xv

NAME

SYNTAX

NOTE

DESCRIPTION

SECTION 1: OVERVIEW

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display an image in a window on the screen

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display an image on the root window, in a variety of styles

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grab any rectangular portion of the screen and turn it into an image

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arbitrarily stretch or compress the image

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rotate the image in 90-degree steps

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flip the image around the horizontal or vertical axes

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crop a rectangular portion of the image

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magnify any portion of the image by any amount, up to the size of the screen

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determine pixel values and x,y coordinates in the image

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adjust image brightness and contrast with a gamma correction function

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apply different gamma functions to the Red, Green, and Blue color components, to correct for non-linear color response

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adjust global image saturation

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perform global hue remapping

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perform histogram equalization

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edit an image's colormap

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reduce the number of colors in an image

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dither in color and b&w

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smooth an image

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crop off solid borders automatically

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convert image formats

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generate Encapsulated PostScript

Unfortunately the Automatic Checkbook Balancing Module still isn't completely debugged, and is not included in this distribution.  

SECTION 2: STARTING XV

Section 2.1: Displaying Pixel Values

196, 137 = 191,121,209 (287 42 81 HSV)

The first pair of numbers (196,137) are the x and y positions of the cursor, in image coordinates. These numbers remain the same regardless of any image resizing, or cropping. For example, if you click on the eye of the fish on the right side of the default image, you'll get (approximately) 251,129 regardless of the size of the displayed image. This allows you to zoom in for precise measurements. The first triplet of numbers (191,121,209) are the RGB values of the selected pixel. The components will have integer values in the range 0-255. The values displayed are prior to any HSV/RGB modification, but after any colormap changes. See "Section 5: The Color Editor" for details. The second triplet of numbers (287 42 81) are the HSV values of the selected pixel. The first component will have integer values in the range 0-359, and the second and third components will have integer values in the range 0-100. The values displayed are prior to any HSV/RGB modification, but after any colormap changes. See "Section 5: The Color Editor" for details. Also, see "Appendix D: RGB and HSV Colorspaces" for more information about what these numbers mean. Note: If you actually want to measure some pixels, it will probably help to crop to a small region of your image, and expand that region to the point where you can see the individual pixels. This string is automatically copied to your X server's cut buffer whenever you measure pixel values. This lets you easily feed this information to another program, useful if you're doing manual feature extraction, or something. Try it: measure a pixel's value, and then go click your Middle mouse button in an xterm window.  

Section 2.2: Cropping

114x77 rectangle starting at 119,58

that would mean that the current cropping rectangle is 114 image pixels wide, 77 image pixels high, and its top-left corner is located 119 image pixels in from the left edge of the image, and 58 image pixels in from the top edge. These values will be updated as you drag the cropping rectangle around. If you want to set the size or position of the cropping rectangle precisely, you can use the arrow keys on your keyboard. First, make the xv info window visible as described above (if it's not already visible). Second, use the mouse to draw a rough approximation of the cropping rectangle that you want. You can now use the arrow keys to move the cropping rectangle around the image. Once you've gotten the top and left sides of the cropping rectangle precisely where you want them, you can move the bottom-right corner of the cropping rectangle (only) by holding the <shift> key down while using the arrow keys. Pressing the up arrow will make the rectangle shorter, and pressing the down arrow will make the rectangle taller. Once you have a cropping rectangle that you can live with, you can proceed with the actual cropping operation. Click the Crop button in the xv controls window, or type the 'c' key in any open xv window. The image window will shrink to show only portions of the image that were inside the cropping rectangle. Note: if you are running a window manager such as mwm, which decorates windows with a title bar, resizing regions, and such, it is quite possible that the aspect ratio of the cropped image will get screwed up. This is because certain window managers enforce a minimum window size. If you try to crop to a rectangle that is too small, the window manager will create the smallest window it can, and the image will be stretched to fit this window. If this happens, you can press the Aspect button in the xv controls window, or type the 'a' key in any open xv window. This will expand the image so that it has the correct aspect ratio again. You can crop a cropped image by repeating the same steps (drawing a new cropping rectangle and issuing the Crop command), ad infinitum. You can return to the original, uncropped image by using the UnCrop command. Simply click the UnCrop button or type the 'u' key in any open xv window. Note that using the UnCrop command will turn off image smoothing (the Smooth) command), due to the potentially long time it can take to generate a large, smoothed image. Note that if you try to make the cropping rectangle too small in either width or height (under 5 screen pixels), it'll just turn itself off. If you want to crop a very small portion of an image, you'll probably have to do it in two passes. First, crop to a small (but large enough to still be enabled) rectangle, expand that region, then crop again.  

Section 2.3: Zooming

SECTION 3:   THE CONTROL WINDOW

Section 3.1: Resizing Commands

Normal (Keyboard equivalent 'n')

Attempts to return the image to its normal size, where one image pixel maps to one screen pixel. For example, if the image (or the current cropped portion of the image) has a size of 320x200, this command will attempt to make the image window be 320 screen pixels wide by 200 screen pixels high. This command may fail in two cases. If you're running a window manager (such as mwm) that enforces a minimum window size, and the 'normal' size is too small, the image may get distorted. See the note in "Section 2.2: Cropping" for more information. Also, if the image is larger than the size of your screen, it will be 'halved' until it fits on the screen. For example, if you try to display a 1400x900 image on a 1280x1024 screen, the Normal command will display a 700x450 image.

Max Size (Keyboard equivalent 'm')

This command will make the displayed image be the same size as the screen. If you are running a window manager that puts up a titlebar, you'll find that the titlebar is now off the top of the screen. To get the titlebar back, simply shrink the image to anything smaller than the size of the screen. The window will be moved so that the titlebar is once again visible.

Maxpect (Keyboard equivalent 'M')

Makes the image as large as possible, while preserving the aspect ratio. This avoids the generally unwanted image distortion that Max Size is capable of generating. For example, if you have a 320x200 image, and an 1280x1024 screen, doing the Maxpect command will result in an image that is 1280x800. Max Size, on the other hand, would've generated an image of size 1280x1024, which would be appear 'stretched' vertically.

Dbl Size (Keyboard equivalent '>')

Doubles the current size of the image, with the constraint that neither axis is allowed to be larger than the screen. For example, given a 320x200 image and a 1280x1024 screen, the image can be doubled once (to 640x400), a second time (to 1280x800), but a third time would make the image 1280x1024. You'll note that on the third time, the width didn't change at all, since it was already at its maximum value. Also note that the height wasn't allowed to double (from 800 to 1600), but was truncated at its maximum value (1024).

Half Size (Keyboard equivalent '<')

Halves the current size of the image, with the constraint that neither axis is allowed to have a size less than 1 pixel. Also, you may run into 'minimum size' problems with your window manager. See the note in "Section 2.2: Cropping" for more information. Note that the window size is maintained as a pair of integers. As a result you may see some integer round-off problems. For example, if you halve a 265x185 image, you'll get a 132x92 image, which is just fine. However, if you Dbl Size this image, you'll get a 264x184 image, not the 265x185 image you might have expected.

+10% (Keyboard equivalent '.')

Increases the current size of the image by 10%, subject to the constraint that the image cannot be made larger than the screen size (in either axis). For example, issuing this command on a 320x200 image will result in a 352x220 image.

-10% (Keyboard equivalent ',')

Decreases the current size of the image by 10%. Neither axis of the image is allowed to shrink below 1 pixel. Also, you run the risk of running into 'minimum window size' problems with your window manager. It should be noted that the +10% and -10% commands have no concept of an 'original size'. They simply increase or decrease the current image size by 10%. As a result, they do not undo each other. For example, take a 320x200 image. Do a +10% and the image will be 352x220. If you issue the -10% command now, the image will be made (352 - 35.2)x(220 - 22), or 316x198.

4x3 (Keyboard equivalent '4')

Attempts to resize the image so that the ratio of width to height is equal to 4 to 3. (e.g., 320x240, 400x300, etc.) This is useful because many images were meant to fill the screen of whatever system they were generated on, and nearly all video tubes have an aspect ratio of 4:3. This command will stretch the image so that things will probably look right on your X display (nearly all of which, thankfully, have square pixels). This command is particularly useful for images which have really bizarre sizes (such as the 600x200 images presumably meant for CGA, and the 640x350 16-color EGA images).

Aspect (Keyboard equivalent 'a')

Applies the 'default aspect ratio' to the image. This is done automatically when the image is first loaded. Normally, the default aspect ratio is '1:1', but certain GIF files may have an aspect ratio encoded in them. You can also set the default aspect ratio via a command-line argument or an X resource. See 'Section 9: Modifying XV Behavior' for more info. The idea behind this command is that you'd stretch the image manually (via your window manager) to roughly the size you'd like, and then use the Aspect command to fix up the proportions. Normally Aspect expands one axis of the image to correct the aspect ratio. If this would result in an image that is larger than the screen, the Aspect command will instead shrink one of the axes to correct the aspect ratio.

Section 3.2: Rotate/Flip Commands

Turn CW (Keyboard equivalent 't')

Rotates the image 90 degrees clockwise.

Turn CCW (Keyboard equivalent 'T')

Rotates the image 90 degrees counter-clockwise.

Flip H (Keyboard equivalent 'h')

Flips the image horizontally (around the vertical center-line of the image).

Flip V (Keyboard equivalent 'v')

Flips the image vertically (around the horizontal center-line of the image).

Section 3.3: Smoothing Commands

Raw (Keyboard equivalent 'r')

Returns the displayed image to its 'raw' state (where each pixel in the displayed image is as close as possible to the corresponding pixel in the internal image). In short, it turns off any dithering or smoothing. When dithering or smoothing haven't been done, this command is disabled.

Dither (Keyboard equivalent 'd')

Regenerates the displayed image by dithering with the available colors in an attempt to approximate the original image. This is only relevant if the color allocation code failed to get all the colors it wanted. If it did get all the desired colors, the Dither command will just generate the same display image as the Raw command. On the other hand, if you didn't get all the desired colors, the Dither command will try to approximate the missing colors by dithering with the colors that were obtained. If you're running xv on a 1-bit display the Dither command will be disabled, as the image will always be dithered for display.

Smooth (Keyboard equivalent 's')

Smooths out distortion caused by integer round-off when an image is expanded or shrunk. This is generally a desirable effect, however it is fairly time-consuming on large images on most current workstations. As such, by default, it is not done automatically. See "Section 9: Modifying XV Behavior" for more details.

Section 3.4: Cropping Commands

Crop (Keyboard equivalent 'c')

Crops the image to the current cropping rectangle. This command is only available when a cropping rectangle has been drawn on the image. See "Section 2.2: Cropping" for further information.

UnCrop (Keyboard equivalent 'u')

Returns the image to its normal, uncropped state. This command is only available after the image has been cropped. See "Section 2.2: Cropping" for further information.

AutoCrop (Keyboard equivalent 'A')

Crops off any constant borders that exist in the image. It will crop to the smallest rectangle that encloses the 'interesting' section of the image. It may not always appear to work because of minor invisible color changes in the image. As such, it works best on computer-generated images, and not as well on scanned images.

Section 3.5: The Display Modes Menu

Window

Displays the image in a window. If you were previously in a 'root' mode, the root window will also be cleared.

Root: Tiled

The image is displayed in the root window. One image is displayed aligned with the top-left corner of the screen. The image is then duplicated towards the bottom and right edges of the screen, as many times as necessary to fill the screen.

Root: Integer Tiled

Similar to Root: Tiled, except that the image is first shrunk so that its width and height are integer divisors of the screen's width and height. This keeps the images along the bottom and right edges of the screen from being Normal, Dbl Size, etc.) will lose the 'integer'-ness of the image.

Root: Mirrored

Tiles the original image with versions that have been horizontally flipped, vertically flipped, and both horizontally and vertically flipped. This gets rid of the sharp dividing lines where tiled images meet. The effect is quite interesting.

Root: Integer Mirrored

Like Root: Mirrored, but also does the integer-ization described under the Root: Integer Tiled entry.

Root: Center Tiled

Like Root: Tiled, but it positions the images so that one of them is centered on the screen, and the rest are tiled off in all directions. Visually pleasing without the image size distortion associated with Root: Integer Tiled.

Root: Centered

Displays a single image centered in the root window, surrounded by black.

Root: Centered, Warp

Displays a single image centered in the root window, surrounded by a black and white 'warp' pattern, which produces some mildly visually pleasing Moire effects.

Root: Centered, Brick

Displays a single image centered in the root window, surrounded by a black and white 'brick' pattern.

Note: The three 'centered' modes (Root: Centered, Root: Centered, Warp, and Root: Centered, Brick, but not Root: Center Tiled) require the creation of a Pixmap the size of the screen. This can be a fairly large request for resources, and will fail on a color X terminal with insufficient memory. They can also require the transmission of considerably more data than the other 'root' modes. If you're on a brain-damaged X terminal hanging off a slow network, you should probably go somewhere else. Barring that, you should certainly avoid the 'centered' modes. Also note: If you quit xv while displaying an image on the root window, the image will remain in the root window, and the colors used by the image will remain allocated. This is generally regarded as correct behavior. If you decide you want to get rid of the root image to free up resources, or simply because you're sick of seeing it, the quickest route is to use run 'xv -clear', which will clear the root window, release any allocated colors, and exit. Alternately, xsetroot and any other X program that puts things in the root window should be able to do the trick as well.  

Section 3.6: The 24-bit Conversion Menu

Fast

Converts 24-bit images into 8-bit images by dithering with a fixed 6x6x6 RGB colormap. It is the quickest of the three algorithms, but also generally produces the worst images. It can also be selected via the '-quick24' command-line option or X resource.

Slow

The default algorithm. Takes about twice as long as the fast algorithm. Uses the median-cut algorithm to pick a set of 256 colors, and then dithers using these colors. It can be selected via the '-slow24' command-line option or X resource.

Best

By far and away the slowest of the algorithms. It can take up to ten times as long as the 'slow' algorithm. It uses a cleverer version of the median-cut algorithm to pick a better set of colors than the slow algorithm. It does not dither. This might look best if you're going to be expanding the image by very much, as the dithering in the other two algorithms becomes very noticable. You can also select this option via the '-best24' command-line option or X resource.

Section 3.7: Working With Multiple Files

Section 3.7.1: Operating a List Window

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clicking in the top or bottom arrow of the scrollbar scrolls the list by one line in the appropriate direction. It will continue to scroll the list as long as you hold the mouse down.

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The thumb (the small white rectangle in the middle of the scrollbar) shows roughly where in the list you are. You can change your position in the list by clicking and dragging the thumb to another position in the scrollbar. The list will scroll around as you move the thumb.

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You can scroll the list up or down a page at a time by clicking in the grey region between the thumb and the top or bottom arrows.

If you click on a name in the list, that name will become highlighted. You can drag the highlight bar up and down, and the list will scroll appropriately. It is also possible to control the list window from the keyboard. In all cases, you must make sure that the window sees the keypress. Generally, this means you have to have the cursor inside the window, though your window manager may also require you to click inside the window first.

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The up and down arrow keys move the highlight bar up and down. If the bar is at the top or bottom of the window, the list will scroll one line.

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The page up and page down keys scroll the list up or down a page at a time.

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Pressing the home key will jump to the beginning of the list. Pressing the end key will jump to the bottom of the list.

Section 3.7.2: The File Commands

Next (Keyboard equivalent <space>)

Attempts to load the next file in the list. If it is unable to load the next file, it will continue down the list until it successfully loads a file. If it gets to the bottom of the list without successfully loading a file, it will put up the default image.

Previous (Keyboard equivalent <backspace>)

Attempts to load the previous file in the list. If it is unable to load the previous file, it will continue up the list until it successfully loads a file. If it gets to the top of the list without successfully loading a file, it will put up the default image.

Delete (Keyboard equivalent <ctrl-D>)

This command lets delete the currently selected file from the list (and optionally delete the associated disk file). Note that the currently selected file is the one with the highlight bar on it. While this is generally the same as the currently displayed image, it doesn't have to be. The Delete command will pop-up a window asking you what you want to delete. Your choices are:

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List Entry, which will remove the highlighted name from the list. (Keyboard equivalent: the enter key)

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Disk File, which will remove the highlighted name from the list and also delete the associated disk file. This removes unwanted images, just like manually typing 'rm <filename>' in another window. (Keyboard equivalent: <ctrl-D>)

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Cancel, which lets you get out of the Delete command without actually deleting anything. (Keyboard equivalent: the esc key)

Section 3.7.3: Image Reloading

Section 3.8: The Grab Command

Section 3.9: Other Commands

Info (Keyboard equivalent 'i')

Opens and closes the xv info window. See "Section 4: The Info Window" for more details.

ColEdit (Keyboard equivalent 'e')

Opens and closes the xv color editor window. See "Section 5: The Color Editor" for more details.

Load (Keyboard equivalent <ctrl-L>)

Opens the xv load window. See "Section 6: The Load Window" for more details.

Save (Keyboard equivalent <ctrl-S>)

Opens the xv save window. See "Section 7: The Save Window" for more details.

Quit (Keyboard equivalent 'q')

Quits out of the program.

SECTION 4:      THE INFO WINDOW

Section 4.1: Overview

Section 4.2: The Fields

Got all 67 desired colors. (66 unique)

This means that 67 entries in the image's colormap were used in the image, but that only 66 of these colors were different, as far as the X server was concerned. See "Appendix E: Color Allocation" for a complete discussion of how colors are allocated, and what the "Colors" field can tell you. Note that the fields are filled in as information becomes available. As such, they can be used as a rough 'progress indicator' when loading images. When you begin loading, all the fields are cleared. Once the image has been successfully loaded, the top three fields (Filename, Format, Resolution) are filled in. Once the colors have been allocated, and the display image generated, the bottom three fields are shown (Cropping, Expansion, and Colors).  

Section 4.3: Status Lines

SECTION 5:     THE COLOR EDITOR

Section 5.1: Overview

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Colormap Editing: This tool lets you arbitrarily modify individual colormap entries. Useful for modifying the color of captions or other things that have been added to images. Also works well on images that have a small number of colors, such as images generated by 'drawing' or CAD programs. It's also an easy way to spiff up boring 1-bit black and white images.

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HSV Modification: This tool lets you alter the image globally in the HSV colorspace. (See "Appendix D: RGB and HSV Colorspaces" for more info.) Here are examples of the sort of things you can do with this tool:

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turn all the blues in an image into reds

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change the tint of an image

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change a greyscale image into a mauve-scale image

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increase or decrease the amount of color saturation in an image

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change the overall brightness of an image

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change the overall contrast of an image

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RGB Modification: This tool lets you route the red, green, and blue color components of an image through independent mapping functions. The functions can either be the standard gamma function, or any arbitrary function that can be drawn with straight line segments or a cubic spline. See "Section 5.3.4: The Intensity Graph" for more info about graph functions.

The major use of the RGB Modification tool is to correct for the differing color response curves of various color monitors, printers, and scanners. This is the tool to use when "the image is too red", for instance. These three tools are tied together in a fixed order. The Colormap Editing tool operates on the original colors in the image. The output of this tool is piped into the HSV Modification tool. Its output is piped into the RGB Modification tool. The output from the RGB Modification tool is what actually gets displayed. In addition there is a collection of buttons that control the xv color editor as a whole (more or less). Don't Panic! It's not as complicated as it looks.  

Section 5.2: The Colormap Editing Tool

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View the 'default' image by running xv without specifying any filenames.

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Open the xv color editor window, and Left click on the first color cell.

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Turn this color cell red by setting the RGB dials to 255,0,0.

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Left click on the 64th color cell (the rightmost color cell in the last complete row).

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Turn this color cell yellow by setting the RGB dials to 255,255,0.

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Middle click on the first color cell. A smooth series of yellowish-reds will be generated from the 64th color cell to the first color cell. Note that the 'direction' doesn't matter.

Since certain images will have many colors that are the same, or nearly the same, it is sometimes convenient to group color cells together. Grouped color cells all take on the same color, and changing any one of them affects all of the other colors in the group. To group color cells together, do the following:

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Hold down the <shift> key.

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Left click on one color cell that you would like to be in the group

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Right click on other color cells that you wish to be in this group. (Right clicking on cells that are already selected will de-select them.)

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Release the <shift> key when you're done.

You can create as many groups as you like. You can use this grouping/ungrouping technique to copy colors from one color cell to another. Left click on the source color cell, Right click on the destination color cell, and Right click on the destination color cell again (to ungroup it).  

Section 5.2.1: Using the Dial Controls

Section 5.2.2: Colormap Editing Commands

ColUndo

Undoes the last change made to the colormap that resulted in a color cell changing value. This includes grouping and ungrouping color cells, and changing any of the dials.

Revert

Undoes all color changes. Returns the colormap to its original state. Destroys any groups that you may have created.

RGB/HSV

Toggles the Colormap Editing dials between editing colors in terms of Red, Green, and Blue, and editing colors in terms of Hue, Saturation, and Value.

Grey

Turns color images into greyscale images by changing the colormap. This replaces each color cell with a greyscale representation of itself. Use the Revert command to restore the colors.

RevVid

This command behaves differently, depending on the setting of the RGB/HSV mode. (You can tell which mode you're in by the titles on the dials.) In RGB mode, each color component is separately 'inverted'. For example, Yellow (which is composed of full red, full green, and no blue) would turn to Blue (no red, no green, full blue). In HSV mode, only the Value (intensity) component is 'inverted'. The Hue and Saturation components remain the same. In this mode, bright colors turn to dark versions of the same color. For example, a Yellow would turn Brown.

Random

Generates a random colormap. This is of questionable usefulness, but it will occasionally come up with pleasing color combinations that you never would've come up with yourself. So it stays in. It works best on images with a small number of colors. Note that it respects cell groupings, so if your image has a lot of colors, you can create a few large groups and then use the Random command.

Note: It is HIGHLY RECOMMENDED that if you're using the Colormap Editing tool, you do NOT use the HSV Modification tool or the RGB Modification tool as well. If you do, the results can be quite confusing. For example, you might edit a color cell, and set its color values to produce a purple. However, because of HSV/RGB Modification further down the line, the actual color displayed on the image (and in the color cell) is yellow. Very confusing, indeed.  

Section 5.3: The HSV Modification Tool

Section 5.3.1: Hue Remapping Controls

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As a simple example of the sort of things you can do with the hue remapping control, we'll change the background color of the default (xv logo) image without changing any other colors in the image. Since the background is composed of a gradient of 64 colors, you would not want to do this with the Colormap Editing tool. It would take forever.

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First, get the default image up on the screen by running 'xv' without giving any filenames. Open up the xv color editor window via the ColEdit command.

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Next, click the mouse in the image window and drag it around. You'll see that all the background pixels have the same Hue component value (240).

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To remap this hue, simply adjust the From dial so that its range includes this Hue value. The background should change from 'blue' to a reddish color, assuming the To dial is still set to its default range (centered around 'R'). If more than the background changed color, you can shrink the From range so that it covers fewer colors. In fact, it's possible to shrink the range to the point where it only covers only a single value.

Note that the values printed when you are tracking pixel values in the image are the values before the HSV Modification tool is applied. For example, the background of the default image will still claim to be blue, regardless of what color you may have changed it to. This is so that you know what Hue value you will need to remap if you want to change its color again. If you press the Reset button that is located near the hue remapping controls, it will effectively disable the hue remapping by setting the To range equal to the From range. Below the hue remapping controls are a group of 'radio buttons'. You can have up to six different hue remappings happening simultaneously. Higher numbered mappings take precedence over lower number mappings. An example of multiple hue remappings:

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Draw a From range that is a complete circle. The easiest way to do this is to draw a range that is nearly a full circle, then click and hold down the 'increase range' button located below the From range dial until the range stops getting bigger.

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Copy this range to the To range by pressing the Reset button.

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Rotate the To range slightly, by either clicking and dragging anywhere in the To range dial, or by using the 'rotate clockwise' and 'rotate counter-clockwise' buttons located below the To range.

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You've just built yourself what is effectively a tint control.

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Now, suppose, you'd like to adjust the background color of your (tint-modified) image, without affecting anything else. Clicking on the background in the image window reveals that the background still has an (original) hue of 240. To modify this hue without affecting anything else, we'll need a second hue remapping.

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Click on the 2 radio button. The dials will change to some other default setting. As before, set the From range to encompass the value 240, preferably as 'tightly' as possible, and set the To range to produce the desired background color.

Note that the six hue remappings are not 'cascaded'. The output of one remapping is not fed as input into any of the other hue remappings. The hue remappings always operate on the hue values in the original image. In this example, if remapping #1 adds 32 to all hue values, thereby mapping the blue background (value 240) into a purple-blue (value 272), remapping #2 still sees the background at 240, and can remap it to anything it likes. Similarly, in the same example, if remapping #1 has mapped a green-blue color (value 208) into blue (value 240), remapping #2 will not map this into another color. As far as remapping #2 is concerned, that green-blue is still green-blue. If it seems complicated, I'm sorry. It is.  

Section 5.3.2: The White Remapping Control

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Press the Grey control in the Colormap Editing tool. This turns all the colors in the image into shades of grey.

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Drag the handle in the white remapping control halfway down towards the 'R' mark. The Hue and Saturation values should be roughly 0-degrees and 50%. The image should now be displayed in shades of pink.

Section 5.3.3: The Saturation Control

Section 5.3.4: The Intensity Graph

Y = 255 * (I/255) ^ (1/g)

where I is the input value (0-255), g is the gamma value, and Y is the computed result. Gamma values (for our purposes) can range between 0 and 10000, non-inclusive.

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A gamma value of '1.00' results in the normal 1:1 straight line.

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Gamma values of less than 1.00 but greater than 0.00 result in 'exponential' curves, which will dim the image.

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Gamma values greater than 1.00 result in 'logarithmic' curves, which will brighten the image. Try it and see.

There is a shortcut for the 'Gam' button. Type 'g' while the mouse is inside the graph window. Also, touching any of the handles after a 'Gam' command will put the graph back into its 'normal' mode. (Either 'spline' or 'lines' depending on which of the top two buttons is turned on.) Generally, whenever you move a graph handle and let go of it, the image will be redrawn to show you the effects of what you've done. This can be time-consuming if you intend to move many points around. You can temporarily prevent the redisplay of the image by holding down a <shift> key. Continue to hold the <shift> key down while you move the handles to the new position. Release the <shift> key when you're done, and the image will be redisplayed.  

Section 5.4: The RGB Modification Tool

*

Adjust the Red graph so that there is a strong red presence on the right side of the graph, and none on the left, or in the middle.

*

Adjust the Green graph so that there is a strong green presence in the middle of the graph, and none on the left or right.

*

Adjust the Blue graph so that there is a strong blue presence on the left side of the graph, and none on the left, or in the middle.

You now have a transformation that will take greyscale images and display them in pseudo-color, using a 'temperature' color scheme. Neato!  

Section 5.5: The Color Editor Controls

Apply (Keyboard equivalent 'p')

Displays the image using the current HSV and RGB Modifications. Also turns the 'Display with HSV/RGB mods' checkbox on. (See below.) This is only useful when the 'Auto-apply HSV/RGB mods' checkbox is off.

NoMod

Displays the image without any HSV or RGB Modifications. Also turns the 'Display with HSV/RGB mods' checkbox off.

Reset (Keyboard equivalent 'R')

Resets all HSV and RGB controls to their default settings. Doesn't affect the Colormap Editing tool.

Undo

Undoes the last change to the HSV or RGB controls. It may be helpful to think of xv as maintaining a series of 32 'snapshots' of the HSV and RGB controls. You are normally looking at the last frame in this series. The Undo control moves you backwards in the series.

Redo

Only available after you've hit Undo. Moves you forward in the 'snapshot' series described above. Note that if you have hit Undo a few times (i.e., you're now looking at some frame in the middle of the series), and you change an HSV or RGB control, all subsequent frames in the series are thrown away, and the current state becomes that last frame in the series.

1,2,3,4

Pressing any of these buttons recalls a preset (a complete set of values for the HSV and RGB controls).

Set

Used in conjunction with the Reset,1,2,3,4 buttons to store the current settings of the HSV and RGB controls into a preset. To do so, press the Set button, and then press one of the Reset,1,2,3,4 buttons. The current HSV and RGB control settings will be stored in that preset, as long as xv continues running. The values will be lost when the program exits. It is also possible to save these values permanently. See the CutRes button (below) and "Section 9: Modifying XV Behavior" for more details.

CutRes

Copies the current settings of the HSV and RGB controls, as text, into the X server's cut buffer. You can then use a text editor to paste these values into your '.Xdefaults' (or '.Xresources') file. This lets you save the current settings 'permanently'. See "Section 9: Modifying XV Behavior" for more details.

Close

This button closes the xv color editor window.

Brite

Brightens the image by moving all the handles in the Intensity graph up by a constant amount.

Dim

Darkens the image by moving all the handles in the Intensity graph down by a constant amount.

Sharp

Increases the contrast of the image by moving handles on the left side of the Intensity graph down, and handles on the right side up.

Dull

Decreases the contrast of the image by moving handles on the left side of the Intensity graph up, and handles on the right side down.

Norm (Keyboard equivalent 'N')

Normalizes the image so that the darkest pixels in the image are given an intensity of '0', and the brightest pixels in the image are given an intensity of '255'. Intermediate colors are interpolated accordingly. This forces the image to have the full (maximum) dynamic range.

HistEQ (Keyboard equivalent 'H')

Runs a histogram equalization algorithm on the currently displayed region of the image. This is, if you're cropped, it will only run the algorithm on the cropped section. Note, however, that the only modification it makes to the image is to generate a bizarre corrective Intensity curve. As such, if you HistEQ a section of the image, then UnCrop, the rest of the image will probably not be what you'd want. Also note that the histogram curve will 'go away' if you touch any of the handles in the Intensity graph window, just like a 'gamma' curve would.

The 'Display with HSV/RGB mods' checkbox tells you whether or you're looking at a modified image (checked) or the 'raw', unmodified image (unchecked). The Apply and NoMod buttons change the setting of this checkbox, and you can also change the checkbox directl by clicking on it. The 'Auto-apply HSV/RGB mods' checkbox controls whether or not the program regenerates and redisplays the image after each change to an HSV or RGB control. By default, this checkbox is turned on, so that you can easily see the results of your modifications. However, in the case that you want to make a large number of changes at once, it might be preferable to turn automatic redisplay off for a while, to speed things up. The 'Auto-reset on new image' checkbox controls whether or not the HSV and RGB controls are Reset back to their default values whenever a new image is loaded up. By default, this is also turned on, as when you're playing with the HSV/RGB controls, you probably only want to affect the current image, and not all subsequently loaded images as well.  

SECTION 6: THE LOAD WINDOW

Ctrl-F moves the cursor forward one character

Ctrl-B moves the cursor backward one character

Ctrl-A moves the cursor to the beginning of the line

Ctrl-E moves the cursor to the end of the line

Ctrl-D deletes the character to the right of the cursor

Ctrl-U clears the entire line

Ctrl-K clears from the cursor position to the end of the line.

If the filename is so long that it cannot be completely displayed in the text entry region, a thick line will appear on the left or right side (or both sides) of the region to show that "there's more over this way". Pressing the Rescan button will rescan the current directory. While the contents of the current directory are read each time the load window is opened, it is perfectly possible (given a multitasking operating system) that some other program may add, delete, or rename files in the current directory. XV would not know if this happened. The Rescan button gives you an easy way of 'kicking' xv into looking again.  

SECTION 7: THE SAVE WINDOW

Full Color

Saves the image as currently shown with all color modifications, cropping, rotation, flipping, resizing, and smoothing. The image will be saved with all of its colors, even if you weren't able to display them all on your screen. For example, you can load a color image on a 1-bit B/W display, modify it, and write it back. The saved image will still be full color, even though all you could see on your screen was some B/W-dithered nightmare.

Greyscale

Like Full Color, but saves the image in a greyscale format.

B/W Dithered

Like Full Color, but before saving the image xv generates a 1-bit-per-pixel, black-and-white dithered version of the image, and saves that, instead.

Reduced Color

Saves the image as currently shown, with all color modifications, cropping, rotation, flipping, resizing, and smoothing. The image will be saved as shown on the screen, with as many or few colors as xv was able to use on the display. The major purpose of this is to allow special effects (color reduction) to be saved, in conjunction with the '-ncols' command line option. You will probably never need to use this.

Format notes:

GIF

While xv can read both the GIF87a and GIF89a formats, it will only write GIF87a. This is in keeping with the GIF89 specification, which states that if you don't need any of the features added in GIF89 (which xv doesn't), you should continue to write GIF87, for greater compatibility with old GIF87-only readers. Since GIF only supports one format (up to 8 bits per pixel, with a colormap), there will be no size difference between a Full Color and a Greyscale image. A B/W Dithered image, on the other hand, will be considerably smaller.

PM

Full Color images are saved in the 3-plane, 1-band, PM_C format. Greyscale and B/W Dithered images are both saved in the 1-plane, 1-band, PM_C format. As such, there is no size advantage to saving in the B/W Dithered format.

PBM (raw)

Full Color images are saved in PPM format. Greyscale images are saved in PGM format. B/W Dithered images are saved in PBM format. Each of these formats are tailored to the data that they save, so PPM images are larger than PGM images, which are in turn larger than PBM images. In the raw variation of the PBM formats, the header information is written in plain ASCII text, and the image data is written as binary data. This is the more popular of the two dialects of PBM.

PBM (ascii)

Like PBM (raw), only the image data is written as ASCII text. As such, images written in this format will be several times larger than images written in PBM (raw). This is a pretty good format for interchange between systems because it is easy to parse. Also, since they are pure, printable ASCII text, images saved in this format can be mailed, without going through a uuencode-like program. Note that xv-produced PBM files may break some PBM readers that do not correctly parse comments. If your PBM reader cannot parse comments, you can easily edit the PBM file and remove the comment lines. A comment is everything from a "#" character to the end of the line.

X11 Bitmap

Saves files in the format used by the bitmap program, which is part of the standard X11 distribution. Since bitmap files are inherently 1-bit per pixel, you can only select the B/W Dithered option for this format.

Sun Rasterfile

Full/Reduced Color images are stored in a 24-bit RGB format, Greyscale images are stored in an 8-bit greyscale format, and B/W Dithered images are stored in a 1-bit B/W format.

PostScript

Full/Reduced Color images are stored in a 24-bit RGB format, Greyscale images are stored in an 8-bit greyscale format, and B/W Dithered images are stored in a 1-bit B/W format. XV writes Encapsulated PostScript, so you can incorporate xv-generated PostScript into many desktop-publishing programs. XV also prepends some color-to-greyscale code, so even if your printer doesn't support color, you can still print 'color' PostScript images. These images will be three times larger (in file size) than their greyscale counterparts, so it's a good idea to save Greyscale PostScript, unless you know you may be printing the file on a color printer at some point. Also, you should probably never need to generate B/W Dithered PostScript, as every PostScript printer I've ever heard of can print greyscale images. The only valid cases I can think of are: A) doing it for a special effect, and B) doing it to generate a much smaller (roughly 1/8th the size) PostScript file. Note: When you try to save a PostScript file, the xv postscript window will pop up to let you specify how you want the image printed. (See "Section 8: The PostScript Window", for details.)

JPEG

XV writes files in the JFIF format created by the Independent JPEG Group. Full/Reduced Color images are written in a 24-bit RGB format, and Greyscale images are written in an 8-bit greyscale format. B/W Dithered images should not be used, as they will probably wind up being larger than Greyscale versions of the same images, due to the way JPEG works. Note: You cannot write Reduced Color JPEG files. If you attempt to, a Full Color JPEG file will be saved. When you save in the JPEG format, a dialog box will pop up and ask you for a quality setting. '75%' is the default value, and really, it's a fine value. You shouldn't have to change it unless you're specifically trying to trade off quality for compression, or vice versa. The useful range of values is 5%-95%.

TIFF

Full/Reduced Color images are written in a 24-bit RGB format, Greyscale images are written in an 8-bit greyscale format, and B/W Dithered images are written in a 1-bit B/W format. When you save in the TIFF format, a dialog box will pop up and ask you which type of image compression it should use. None, LZW, and PackBits compression types are available for Full/Reduced Color, Greyscale, and B/W Dithered modes. In addition, there are two B/W Dithered-only algorithms, CCITT Group3 and CCITT Group4.

SECTION 8: THE POSTSCRIPT WINDOW

SECTION 9: MODIFYING XV BEHAVIOR

Section 9.1: Command Line Options Overview

xv [-] [-2xlimit] [-aspect w:h] [-bg color] [-black color]
  [-bw width] [-cegeometry geom] [-cemap] [-cgeometry geom]
  [-clear] [-cmap] [-cursor char#] [-DEBUG level]
  [-display disp] [-dither] [-expand exp] [-fg color]
  [-fixed] [-geometry geom] [-help] [-hi color] [-hsv]
  [-igeometry geom] [-imap] [-keeparound] [-lo color] [-max]
  [-maxpect] [-mono] [-ncols nc] [-nglobal] [-ninstall]
  [-nopos] [-noqcheck] [-owncmap] [-perfect] [-quit] [-rbg color]
  [-rfg color] [-rgb] [-rmode mode] [-root] [-rw] [-slow24]
  [-smooth] [-visual type] [-wait seconds] [-white color]
  [-wloop] [-noresetroot] [-browse] [-nostat] [-best24] [-quick24]
  [-cecmap] [-crop] [-rv] [-nolimits] [-loadclear] [filename ...]

Section 9.2: General Options

-help

Print usage instructions, listing the current available command-line options. Any unrecognized option will do this as well.

-display disp

Specifies the display that xv should attempt to connect to. If you don't specify a display, xv will use the environment variable $DISPLAY.

-fg color (Resource name: foreground string)

Sets the foreground color used by the windows.

-bg color (Resource name: background string)

Sets the background color used by the windows.

-hi color (Resource name: highlight string)

Sets the highlight color used for the top-left edges of the control buttons.

-lo color (Resource name: lowlight string)

Sets the lowlight color used for the bottom-right edges of the control buttons, and also the background of some windows.

-bw bwidth (Resource name: borderWidth integer)

Sets the width of the border on the windows. Your window manager may choose to ignore this, however.

Section 9.3: Image Sizing Options

-geometry geom (Resource name: geometry string)

Lets you specify the size and placement of the 'image' window. It's most useful when you only specify a position, and let xv choose the size. If you specify a size as well, xv will create a window of that size, unless -fixed is specified. The geom argument is in the form of a normal X geometry string (e.g. "300x240" or "+10+10" or "400x300+10+10").

-fixed (Resource name: fixed boolean)

Only used in conjunction with the -geometry option. If you specify a window size with the -geometry option, xv will normally stretch the picture to exactly that size. This is not always desirable, as it may seriously distort the aspect ratio of the picture. Specifying the -fixed option corrects this behavior by instructing xv to use the specified geometry size as a maximum window size. It will, however, preserve the original aspect ratio of the picture. For example, if you give a rectangular geometry of '320x240', and you try to display a square picture with a size of '256x256', the window opened will actually be '240x240', which is the largest square that still fits in the '320x240' rectangle that was specified.

-expand exp (Resource name: expand floating-point)

Lets you specify an initial expansion or compression factor for the picture. You can specify floating-point values. Values larger than zero multiply the picture's dimensions by the given factor. (i.e., an expand factor of '3' will make a 320x200 image display as 960x600). Factors less than zero are treated as reciprocals. (i.e., an expand factor of '-4' makes the picture 1/4th its normal size.). '0' is not a valid expansion factor.

-aspect w:h (Resource name: aspect string)

Lets you set an initial aspect ratio, and also sets the value used by the Aspect control. The aspect ratio of nearly every X display (and, in fact, any civilized graphics display) is 1:1. What this means is that pixels appear to be 'square'. A 100 pixel wide by 100 pixel high box will appear on the screen as a square. Unfortunately, this is not the case with some screens and digitizers. The -aspect option lets you stretch the picture so that the picture appears correctly on your display. Unlike the other size-related options, this one doesn't care what the size of the overall picture is. It operates on a pixel-by-pixel basis, stretching each image pixel slightly, in either width or height, depending on the ratio. Aspect ratios greater than '1:1' (e.g., '4:3') make the picture wider than normal. Aspect ratios less than '1:1' (e.g. '2:3') make the picture taller than normal. (Useful aspect ratio: A 512x480 image that was supposed to fill a standard 4x3 video screen (produced by many video digitizers) should be displayed with an aspect ratio of '5:4')

Section 9.4: Color Allocation Options

-ncols nc (Resource name: ncols integer)

Sets the maximum number of colors that xv will use. Normally, this is set to 'as many as it can get'. However, you can set this to smaller values for interesting effect. Most notably, if you set it to '0', it will display the picture by dithering with 'black' and 'white'. (The actual colors used can be set by the -black and -white options, below.)

-nglobal (Resource name: nglobal boolean)

Adjusts the way the program behaves when it is unable to get all the colors it requested. Normally, it will search the display's default colormap, and 'borrow' any colors it deems appropriate. These borrowed colors are, however, not owned by xv, and as such, can changed without xv's permission, or knowledge. If this happens, the displayed picture will change, in a less-than-desirable direction. If you specify the -nglobal option, xv will not use 'global' colors. It will only use colors that it successfully allocated, which makes it immune to any color changes. It should be noted that 'use global colors' is the default because color changes aren't generally a problem if you are only using xv to display a picture for a short time. Color changes only really become a problem if you use xv to display a picture that you will be keeping around for a while, while you go and do some other work (such as using xv to display a background). In such cases you will want to specify -nglobal. Note: using the -ncols or -root options automatically turn on -nglobal.

-rw (Resource name: rwColor boolean)

Tells xv to use read/write color cells. Normally, xv allocates colors read-only, which allows it to share colors with other programs. If you use read/write color cells, no other program can use the colors that xv is using, and vice-versa. The only reason you'd do such a thing is that using read/write color cells allows the Apply function in the xv color editor window to operate much faster.

-perfect (Resource name: perfect boolean)

Makes xv try 'extra hard' to get all the colors it wants. In particular, when -perfect is specified, xv will allocate and install its own colormap if (and only if) it was unable to allocate all the desired colors. This option is not allowed in conjunction with the -root option.

-owncmap (Resource name: ownCmap boolean)

Like '-perfect', only this option forces xv to always allocate and install its own colormap, thereby leaving the default colormap untouched.

-cecmap (Resource name: ceditColorMap boolean)

Specifies whether xv installs the image's colormap in the xv color editor window, as well as in the image's window. By default, the program does install the colormap in the color editor window, however this can occasionally make the color editor window unreadable. (This option only apples when the '-perfect' or '-owncmap' options create their own colormaps.)

-ninstall (Resource name: ninstall boolean)

Prevents xv from 'installing' its own colormap, when the -perfect or -owncmap options are in effect. Instead of installing the colormap, it will merely 'ask the window manager, nicely' to take care of it. This is the correct way to install a colormap (i.e., ask the WM to do it), unfortunately, it doesn't actually seem to work in many window managers, so the default behavior is for xv to handle installation itself. However, this has been seen to annoy one window manager (dxwm), so this option is provided if your WM doesn't like programs installing their own colormaps.

Section 9.5: 24-bit Conversion Options

-quick24 (Resource name: quick24 boolean)

Forces xv to use the 'quick' 24-bit to 8-bit conversion algorithm. This algorithm dithers the picture using a fixed set of colors that span the entire RGB colorspace. In versions of xv prior to 2.10, this was the default algorithm. It no longer is.

-slow24 (Resource name: slow24 boolean)

Specifies that the 'slow' 24-bit to 8-bit conversion algorithm is to be used by the program. This algorithm uses a version of Heckbert's median cut algorithm to pick the 'best' colors on a per-image basis, and dithers with those. This is the current default conversion algorithm. Advantages: The -slow24 algorithm often produces better looking pictures than the -quick24 algorithm. Disadvantages: The -slow24 algorithm is about half the speed of the -quick24 algorithm. Also, since the colors are chosen on a per-image basis, it can't be used to display multiple images simultaneously, as each image will almost certainly want a different set of 256 colors. The -quick24 algorithm, however, uses the same exact colors for all images, so it can display many images simultaneously, without running out of colors.

-best24 (Resource name: best24 boolean)

Forces xv to use the same algorithm used in the program ppmquant, written by Jef Poskanzer. This algorithm also uses a version of Heckbert's median cut algorithm, but is capable of picking 'better' colors than the -slow24 algorithm, and it doesn't dither. Advantages: Generally produces slightly better images than the -slow24 algorithm. Also, the images are undithered, so they look better when expanded. Disadvantages: Much slower than the -slow24 algorithm. Like, 5 to 10 times slower. The images produced aren't that much better than those produced by the -slow24 algorithm.

-noqcheck (Resource name: noqcheck boolean)

Turns off a 'quick check' that is normally made. Normally, before running either of the 24-bit to 8-bit conversion algorithms, xv determines whether the picture to be displayed has more than 256 unique colors in it. If the picture doesn't, it will treat the picture as an 8-bit colormapped image (i.e., GIF), and won't run either of the conversion algorithms. Advantages: The pictures will be displayed 'perfectly', whereas if they went through either of the conversion algorithms, they'd be dithered. Disadvantages: Often uses a lot of colors, which limits the ability to view multiple images at once. (See the -slow24 option above for further info about color sharing.)

Section 9.6: Root Window Options

-root (Resource name: <none>)

Directs xv to display images in the root window, instead of opening its own window. Exactly how the images will be displayed in the root window is determined by the setting of the -rmode option.

-rmode mode    (Resource name: rootMode integer)

Determines how images are to be displayed on the root window, when
-root has been specified. You can find the current list of 'modes' by using a mode value of '-1'. XV will complain, and show a list of valid modes. The current list at of the time of this writing is:

0:     tiling

1:     integer tiling

2:     mirrored tiling

3:     integer mirrored tiling

4:     centered tiling

5:     centered on a solid background

6:     centered on a 'warp' background

7:     centered on a 'brick' background

The default mode is '0'. See "Section 3.5: The Display Modes Menu" for a description of the different display modes.

-noresetroot (Resource name: resetroot)

Normally, when changing from root to window display mode, the root is set to the standard X crosshatch pattern. Using -noresetroot or setting resetroot to false will force the root to remain. This is useful when comparing between different tiled images.

-rfg color (Resource name: rootForeground string)

Sets the 'foreground' color used in some of the root display modes.

-rbg color (Resource name: rootBackground string)

Sets the 'background' color used in some of the root display modes.

-max (Resource name: <none>)

Makes xv automatically stretch the image to the full size of the screen. This is mostly useful when you want xv to display a background. While you could just as well specify the dimensions of your display ('-geom 1152x900' for example), the -max option is display-independent. If you suddenly decide to start working on a 1280x1024 display (ferinstance) the same command will still work. Note: If you specify -max when you aren't using -root, the behavior is slightly different. The image will be made as large as possible while still preserving the normal aspect ratio.

-maxpect (Resource name: <none>)

Makes the image as large as possible while preserving the aspect ratio.

-quit (Resource name: <none>)

Makes xv display the (first) specified file and exit, without any user intervention. Since images displayed on the root window remain there until explicitly cleared, this is very useful for having xv display background images on the root window in some sort of start-up script. Needless to say, this is only useful if you are using -root.

-clear (Resource name: <none>)

Clears the root window of any extraneous xv images. Note: it is not necessary to do an 'xv -clear' before displaying another picture in the root window. xv will detect that there's an old image in the root window and automatically clear it out (and free the associated colors).

Section 9.7: Window Options

-cmap (Resource name: ctrlMap boolean)

Maps the xv controls window.

-cgeom geom (Resource name: ctrlGeometry string)

Sets the initial geometry of the xv controls window. Note: only the position information is used. The window is of fixed size.

-imap (Resource name: infoMap boolean)

Maps the xv info window.

-igeom geom (Resource name: infoGeometry string)

Sets the initial geometry of the xv info window. Note: only the position information is used. The window is of fixed size.

-cemap (Resource name: ceditMap boolean)

Maps the xv color editor window.

-cegeom geom (Resource name: ceditGeometry string)

Sets the initial geometry of the xv color editor window. Note: only the position information is used. The window is of fixed size.

-nopos (Resource name: nopos boolean)

Turns off the 'default' positioning of the various xv windows. Every time you open a window, you will be asked to position it. (Assuming your window manager asks you such things. mwm, for instance doesn't seem to ask)

Section 9.8: Miscellaneous Options

-mono (Resource name: mono boolean)

Forces the image to be displayed as a greyscale. This is most useful when you are using certain greyscale X displays. While xv attempts to determine if it's running on a greyscale display, many X displays lie, and claim to be able to do color. (This is often because they have color graphics boards hooked up to b/w monitors. The computer, of course, has no way of knowing what type of monitor is attached.) On these displays, if you don't specify -mono, what you will see is a greyscale representation of one of the RGB outputs of the system. (For example, you'll see the 'red' output on our greyscale Sun 3/60s.) The -mono option corrects this behavior.

-white color (Resource name: white string)

Specifies the 'white' color used when the picture is b/w stippled. (When '-ncols 0' has been specified.)

-black color (Resource name: black string)

Specifies the 'black' color used when the picture is b/w stippled. (When '-ncols 0' has been specified.) Try something like: 'xv -ncols 0 -bl red -wh yellow <filename>' for some interesting, late-'60s-style psychodelia effects.

-wait secs (Resource name: <none>)

Turns on a 'slide-show' feature. Normally, if you specify multiple input files, xv will display the first one, and wait for you to give the Next command (or whatever). The -wait option makes xv wait the specified number of seconds, and then go on to the next picture, without any user intervention. The program still accepts commands, so it's possible to 'abort' the current picture without waiting the full specified time by using the Next command.

-wloop (Resource name: <none>)

Normally, when running a slide-show with the -wait option, xv will terminate after displaying the last image. If you also specify the -wloop option, the program will loop back to the first image and continue the slide-show until the user issues the Quit command.

-rgb (Resource name: hsvMode boolean)

Specifies that, by default, the colormap editing dials in the xv color editor window should be in RGB mode. This is the normal default behavior.

-hsv (Resource name: hsvMode boolean)

Specifies that, by default, the colormap editing dials in the xv color editor window should be in HSV mode.

-dither (Resouce name: autoDither boolean)

When specified, tells xv to automatically issue a Dither command whenever an image is first displayed. Useful on displays with limited color capabilities (4-bit and 6-bit displays.)

-smooth (Resource name: autoSmooth boolean)

When specified, tells xv to automatically issue a Smooth command whenever an image is first displayed. This is useful when you are using one of the image sizing options (such as '-expand' or '-max').

-crop (Resource name: autoCrop boolean)

When specified, tells xv to automatically issue an AutoCrop command whenever an image is first displayed.

-visual vistype (Resource name: visual string)

Normally, xv uses the default visual model provided by your X server. You can override this by explicitly selecting a visual to use. Valid types are StaticGray, StaticColor, TrueColor, GrayScale, PseudoColor, and DirectColor. Not all of these are necessarily provided on any given X display. Run xdpyinfo on your display to find out what visual types are supported.

-cursor curs (Resource name: cursor integer)

Specifies an alternate cursor to use in the image window (instead of the normal 'cross' cursor). curs values are obtained by finding the character number of a cursor you like in the 'cursor' font. (Run 'xfd -fn cursor' to display the cursor font.) For example, a curs value of '56' corresponds to the (singularly useless) 'Gumby' cursor.

-keeparound (Resource name: keepAround boolean)

The '-keeparound' option is now poorly named, as I've changed the default behavior. Now, if you Delete the last file in the xv controls list, nothing unexpected will happen. If you specify the '-keeparound' option, which toggles the '-keeparound' flag off, the program will automatically exit as a convenience. It should probably be renamed '-goaway' or something...

-2xlimit (Resource name: 2xlimit boolean)

By default, xv prevents the image window from ever getting larger than the screen. Unfortunately, because of this, if you load an image that is larger than your screen, the image will be shrunk until it fits on your screen. Some folks find this undesirable behavior. Specifying the -2xlimit option doubles the size limitations. The image window will be kept from getting larger than 2x the width and height of your screen. Just in case you're wondering why there's any size limitations: it's fairly easy to accidentally ask for a huge image to be generated. Simply crop a section of the image, zoom so you can see the individual pixels, and uncrop. If there were no size limitations, the (expanded many times) image could be huge, and might crash your X server. At the very least, it would take a long period of time, and freeze your X server during part of it. Generally undesirable behavior.

-nolimits (Resource name: nolimites boolean)

For the truly daring, this turns off all limitations on the maximum size of an image window. (Well, there's still an X-imposed maximum size of 64k by 64k, but that really shouldn't be a problem.) Warning: as mentioned above, it is fairly easy to accidentally generate a huge image when you do an UnCrop command, and you may well crash xv, your X server, the host machine, or all three. Use At Your Own Risk!!!

-rv (Resource name: reverse)

Makes xv display a 'negative' of the loaded image. White becomes black, and black becomes white. Color images will have 'interesting' effects, as the RGB components are individually reversed. For example, red (255,0,0) will become cyan (0,255,255), yellow will become blue, and so on.

-DEBUG level (Resource name: <none>)

Turns on some debugging information. You shouldn't need this. If everything worked perfectly, I wouldn't need this either.

-browse (Resource name: browseMode boolean)

Prevents the xv load window from being closed whenever you successfully load a file. This makes 'browsing' a directory somewhat more pleasant.

-nostat (Resource name: nostat boolean)

Turns off the stat() call is is performed for each file whenever you change directories in the xv load and xv save windows. This is useful if you're on a machine with lots of remote files mounted on it, and you find the directory switching to be too slow.

-loadclear (Resource name: clearOnLoad boolean)

If you were on a PseudoColor display, xv used to automatically clear the image window (or the root window, if you were in a root mode), whenever you loaded a new image. This was to prevent the potentially annoying/confusing 'rainbow' effect that happens when colormap entries are freed and reallocated with different colors. Ths has changed. By default, xv no longer clears the image/root window. This is for two reasons: I've decided that the rainbow effect is semi-entertaining, in that it gives you something to look at while the next image is being loaded. Secondly, if you are viewing a series of images that have the same colors in them, it's possible for xv to animate them (by using the '-wait' command line option), albeit no faster than one frame every 1-2 seconds. For example, you can go get the satellite radar images from vmd.cso.uiuc.edu (in the directory 'wx'), run 'xv -wait 0 -wloop SA*', and voila! Just like the evening news!

-

Specifying '-' all by itself tells xv to take its input from stdin, rather than from a file. This lets you put xv on the end of a Un*x pipe.

Section 9.9: Color Editor Resources

*

Start xv and put it in the background by typing 'xv &'.

*

Type the command 'cat >foo' in an active xterm window

*

Bring the xv color editor window up.

*

Issue the Cut Resources command.

*

Click your Middle mouse button in the xterm window. A set of resource lines describing the current state of the xv color editor controls will be 'pasted' into the window.

*

You could type '<ctrl-D>' in the xterm to complete the cat command, edit this file, and put it in your .Xdefaults/.Xresources file.

The lines generated by Cut Resources will look like the following:
xv.default.huemap1: 330 30 CW 330 30 CW
xv.default.huemap2: 30 90 CW 30 90 CW
xv.default.huemap3: 90 150 CW 90 150 CW
xv.default.huemap4: 150 210 CW 150 210 CW
xv.default.huemap5: 210 270 CW 210 270 CW
xv.default.huemap6: 270 330 CW 270 330 CW
xv.default.whtmap: 0 0 1
xv.default.satval: 0
xv.default.igraf: S 4 : 0,0 : 64,64 : 192,192 : 254,254
xv.default.rgraf: S 4 : 0,0 : 64,64 : 192,192 : 254,254
xv.default.ggraf: S 4 : 0,0 : 64,64 : 192,192 : 254,254
xv.default.bgraf: S 4 : 0,0 : 64,64 : 192,192 : 254,254

These lines completely describe one state of the xv color editor controls. There are five different states that you can specify via X resources. The 'default' state (as shown) holds the settings used whenever the program is first started, and whenever the Reset command is used. You can also store settings in one of the four xv presets (accessed via the '1'-'4' buttons in the xv color editor) by changing the string 'default' in the above lines to 'preset1', 'preset2', 'preset3', or 'preset4' respectively. There are four types of resource described in these lines: huemap, whtmap, satval, and graf.  

Section 9.9.1: Huemap Resources

1.

The 'starting' angle of the From range, in degrees (integer).

2.

The 'ending' angle of the From range, in degrees (integer).

3.

The direction of the From range. Either 'cw' (clockwise) or 'ccw' (counter-clockwise).

4.

The 'starting' angle of the To range, in degrees (integer).

5.

The 'ending' angle of the To range, in degrees (integer).

6.

The direction of the To range. Either 'cw' or 'ccw'.

Section 9.9.2: Whtmap Resources

1.

The hue to remap 'white' to, in degrees (integer).

2.

The saturation to give to the remapped 'white', in percent (integer).

3.

A boolean specifying whether the white remapping control is enabled. If '1', the control is enabled. If '0', the control is disabled.

Section 9.9.3: Satval Resource

Section 9.9.4: Graf Resources

In 'gamma' format, the graf resource takes two parameters:

1.

The letter 'G', specifying 'gamma' mode

2.

A single floating point number specifying the gamma value.

In 'spline/line' mode, the graf resource takes a variable number of parameters:

1.

The letter 'S' specifying 'spline' mode, or the letter 'L' specifying 'line' mode.

2.

An integer number indicating the number of handles (control points) that this graph window will have. (Must be in the range 2-16, inclusive.)

3.

For each handle, there will be a ':', and the x and y positions of the handle, separated by a comma. The x and y positions can be in the range 0-255 inclusive.

Section 9.9.5: Other Resources

LIMITATIONS

It also only displays the first image in GIF files that have multiple images in them.

As for PM pictures, this program only displays 1-plane PM_I pictures, or 1-, 3-, or 4-plane PM_C pictures.

PM FORMAT

The 4-, 6-, 16-, 24-, and 32-bit code has not been extensively tested. (A 4-bit MicroVax GPX system, a 6-bit HP 9000/320, a 16-bit Sony 3710, and a 24-bit HP 9000/350, respectively. The 32-bit code hasn't actually been tested at all.) You won't be able to do '-ncols 0' on a 6-, 16-, 24-, or 32-bit display, not that you should want to.  

AUTHORS

GIF reading code based on gif2ras.c, by Patrick J. Naughton (naughton@wind.sun.com)

GIF writing code essentially unchanged from code written by Michael Maudlin (mlm@cs.cmu.edu).

SUN Rasterfile i/o code written by Dave Heath (heath@cs.jhu.edu)

JPEG interface code written by Markus Baur (s_baur@iravcl.ira.uka.de)

JPEG i/o code provided by the Independent JPEG Group.

TIFF i/o code and interface code written by Sam Leffler (sam@sgi.com)

Portions of 'ppmquant' snarfed for the '-best24' algorithm. ppmquant (and the rest of the pbmplus package) was written by Jef Poskanzer. (jef@well.sf.ca.us)

fsQuick code written and supplied by David B. Rosen (rosen@cns.bu.edu). This code is a very fast implementation of Floyd-Steinberg dithering for 1-bit b/w displays.

Index

NAME

SYNTAX

NOTE

DESCRIPTION

SECTION 1: OVERVIEW

SECTION 2: STARTING XV

Section 2.1: Displaying Pixel Values

Section 2.2: Cropping

Section 2.3: Zooming

SECTION 3:      THE CONTROL WINDOW

Section 3.1: Resizing Commands

Section 3.2: Rotate/Flip Commands

Section 3.3: Smoothing Commands

Section 3.4: Cropping Commands

Section 3.5: The Display Modes Menu

Section 3.6: The 24-bit Conversion Menu

Section 3.7: Working With Multiple Files

Section 3.7.1: Operating a List Window

Section 3.7.2: The File Commands

Section 3.7.3: Image Reloading

Section 3.8: The Grab Command

Section 3.9: Other Commands

SECTION 4:      THE INFO WINDOW

Section 4.1: Overview

Section 4.2: The Fields

Section 4.3: Status Lines

SECTION 5:      THE COLOR EDITOR

Section 5.1: Overview

Section 5.2: The Colormap Editing Tool

Section 5.2.1: Using the Dial Controls

Section 5.2.2: Colormap Editing Commands

Section 5.3: The HSV Modification Tool

Section 5.3.1: Hue Remapping Controls

Section 5.3.2: The White Remapping Control

Section 5.3.3: The Saturation Control

Section 5.3.4: The Intensity Graph

Section 5.4: The RGB Modification Tool

Section 5.5: The Color Editor Controls

SECTION 6: THE LOAD WINDOW

SECTION 7: THE SAVE WINDOW

SECTION 8: THE POSTSCRIPT WINDOW

SECTION 9: MODIFYING XV BEHAVIOR

Section 9.1: Command Line Options Overview

Section 9.2: General Options

Section 9.3: Image Sizing Options

Section 9.4: Color Allocation Options

Section 9.5: 24-bit Conversion Options

Section 9.6: Root Window Options

Section 9.7: Window Options

Section 9.8: Miscellaneous Options

Section 9.9: Color Editor Resources

Section 9.9.1: Huemap Resources

Section 9.9.2: Whtmap Resources

Section 9.9.3: Satval Resource

Section 9.9.4: Graf Resources

Section 9.9.5: Other Resources

LIMITATIONS

PM FORMAT

AUTHORS