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1993-07-02
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NAME
mgif - display colour images in grey scales and manipulate them
SYNOPSIS
mgif -fl [-m] file.fl ...
mgif [flag] ... wildcard ...
flags: -x, -xx, -n, -i, -v, -vers, -c, -w, -p, -p0 n, -p1 n, -h
DESCRIPTION
MGIF 4.2 displays colour images in four grey scales in any of the ST and
Falcon030 bitplane modes, and probably the TT modes as well, using a
flickering technique and Floyd-Steinberg dithering to get fantastic
results. In the Falcon true colour mode 32 grey scales are shown, with
dithering, which looks even better.
For best results at least 640x400 pixels at 60Hz is recommended.
A selection of image processing tools can be aplied to the image to
enhance it or produce interesting effects.
Versions up to 3.7 of this program were written by Bill Rosenkranz, but
development is now continued by Johan Klockars.
The currently supported image file formats are:
GIF - extension .GIF (GIF87a and GIF89a)
JPEG - - " - .JPG or .JPE (only the JFIF file format)
PI1 - - " - .PI1
PI2 - - " - .PI2
FL - - " - .FL (this is MGIF's own format)
OPTIONS
-x Use extra JPEG colour decoding steps to get better results.
Without this option a faster grey scale decoding is used.
This option has no useful effect in this monochrome only version.
-xx The same as -x
-n Do not use dithering in JPEG decoding process.
This option has no useful effect in this monochrome only version.
-i Inquire about the files but do not display them.
Ouput contains information like image size, number of bits per
pixel etc.
-v Show verbose messages.
-vers Show MGIF version information.
-c Do not copy image from the flicker screens to the normal screen at
return to command line mode. Very useful when you run mgif from a
window, such as MiNT/toswin or gemini/mupfel.
-w Wait for key at startup. Useful if you run mgif from floppy and want
to change disk before loading begins.
-p Use pipe for command input instead of the usual interaction.
This is not yet functional.
-p0 n Allocate n Kb memory for the original picture.
The default is about one third of the available memory, but not
more than 1 Mb.
-p1 n Allocate n Kb memory for the new picture.
The default is about one third of the available memory, but not
more than 2 Mb.
-h Show help text.
-fl Load files in MGIF's own flicker file format. If not the -m option
is used, the pictures are shown sequentially.
Press any key to go to the next file.
-m Create a mosaic of flicker files. Several images can be displayed
on one screen if they are all small enough.
Two 320x400, four 320x200 or six 200x200 images are displayed
together. Other sizes are treated as the nearest larger size.
wild One or more standard wildcards with extensions as above. If a file
card has no extension it will be treated as if it was a GIF image.
INTERACTIVE COMMANDS
The following commands are available at the prompt:
Control Commands
h Help
Prints a brief summary of the available commands.
q Quit
Move to the next image given on the command line. If there
are no more the program exits.
<ESC>
Exits the program.
<SPACE>
Draws the current image.
<ENTER>
Shows last drawn image again.
w What
Displays information about image, buffers, load time etc.
hi Histogram
Plots the intensity histogram of the current image.
o Toggle Original
Toggle the current image, original/new.
Transformations are cumulative only if "new" is current.
f File Operations
The only available file operation is to save the last screen
image to a special file having the .FL suffix. This file
will contain the three screen images which are used by the
flicker routine to simulate grey scale.
In order to save an image in this format you must first
display it completely by the flicker routine, ie do not
escape the actual screen draw but let it finish.
cp Copy
Copy the new, transformed image, to the original or the
other way around. The former is the most useful.
Display Options
n Noise
Adds noise. Not to the image itself but to the dithering
process. This can help in images which have artificial
banding as a result of the dithering process. You are asked
for a value which is a percentage (0 to 100).
Each time "o" is toggled, noise is reset zo zero (off).
g Laplace filter
This, like noise, is not applied to the image itself but
rahter in the dithering process. It helps to define hard
edges in images and implements a Laplace filter. A
quantity, Beta, is required. A value of one corresponds to
a Beta of 0.25, a value of two corresponds to a Beta of 0.50
etc. A value of zero turns off Laplace filtering.
It is possible to get the same effect by giving a suitable
matrix to the convolution function.
Beta is reset to zero when "o" is toggled.
Frame Processes
e Enlarge
Enlarges images two times. You can choose which dimensions
should be enlarged as either horizontal, vertical or both.
The new pixels inserted are given the average intensity of
their neighbours.
s Shrink
Reduces images two times. You can choose which dimensions
should be reduces as either horizontal, vertical or both.
Every other point is thrown away when reducing.
z Zoom
Use the arrow keys to move around a window covering one
fourth of the picture to choose which part to enlarge two
times. The shift keys can be used to position the window
with pixel accuracy. When you are satisfied, press the
<INSERT> key. At any time any other key aborts zooming.
cu Cut
Cuts out a rectangular area of the image.
A crosshair can be moved around as described under "zoom"
above to select first the top left corner and then the
bottom right corner. Selection is by the <INSERT> key.
The crosshair can be moved outside the screen area if the
complete image is too large to fit on screen. The coordinates
shown on screen will still show the correct values, but the
crosshair itself will of course not be visible.
r Rotate
Rotate the original (not the new) image any integer angle, from
-180 to 180 degrees, counter clockwise. Any changes done to the
new image are lost, so you'll be asked to confirm the operation
if the new image is the current one.
mi Mirror
You can mirror the image horizontally or vertically.
x Shear (not shown on help screens)
Shear image horizontally or vertically a specified amount.
This is not really documented yet.
y Scale (not shown on help screens)
Scale image horizontally or vertically to a specified size.
This is not really documented yet.
Point Processes
hi Histogram equalization
This operation attempts to smooth out images with skewed
or narrow histograms. The intensity values are redistributed
to match their occurence frequency.
i Inversion
This is a bit mo