Really Useful CD 1/ReallyUsefulCD1.iso/extras/graphics/_greyedit/docs/guide

Text File | 1991-05-08 | 22.3 KB | 585 lines

>Guide
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GreyEdit 1.02                                  ---------------------------
                                                This program is SHAREWARE
Version date : 08 May 1991                     ---------------------------
                                          please refer to the end of this guide

----------------
- Introduction -
----------------
GreyEdit can process and edit 256-level greyscale (digitized) images. In
addition it can grab video images from the Zeridajh Video Digitiser podule,
when this is present.

Several extremely fast filter algorithms, histogram equalization, range
expansion and inversion may be applied to whole images. In addition, noise
pixels may be edited by hand, and sides of images may be cut off, optionally
aided by zoom functions for precise editing.


-------------------------
- Using the application -
-------------------------
To start up GreyEdit, double-click on the '!GreyEdit' icon.

It will install itself on the icon bar, and clicking MENU on the iconbar icon
will give the usual 'Info' and 'Quit' options. Clicking SELECT or ADJUST will
pop up the options menu, but some options will not be selectable at this stage.

GreyEdit accepts and outputs the Clear graphics file format, which plays an
intermediate role in my other image processing applications !Translator and
!Creator. Clear files can also be processed by !ChangeFSI, by Roger Wilson.
Only greyscale, <=8 bits per pixel Clear files are accepted bu GreyEdit. You
can convert any colour image to a greyscale image by using Translator's
'Black and white' option. Refer to the end of this guide for more details.

Loading an image can be done in three ways :
a) by dragging a greyscale Clear file to the GreyEdit icon on the icon bar
b) by dragging a greyscale Clear file to the image window (when an image is
   already loaded)
c) by grabbing an image from a video source using the Zeridajh Video
   Digitiser podule, when this is present (see below)

In addition, output may be to a 'tweaked' 256-colour sprite file, using the
standard palette. Refer to 'Save Sprite' and 'Displaying greyvalues' for
details.

When succesfully processed, the image will appear in a resizable, scrollable
window. The title of the window will indicate the image's (file)name and the
current zoom factors.


-----------------
- The main menu -
-----------------
Clicking MENU on the image window (when an image is loaded) or clicking
SELECT or ADJUST on the iconbar icon will pop up the main menu. All menu
items are explained in detail below.

--------------
| Image info |
--------------
This icon leads to the image info window.

This window shows some information relating to the current image, such
as resolution, size, etc..

--------
| Grab |
--------
This icon gives access to a submenu of options that enable you to grab video
images from the Zeridajh Video Digitiser podule. When the podule is not
present, this icon will be shaded.

---------------
| Grab | Size |
---------------
This icon leads to a submenu in which the size of the image to be grabbed may
be selected. There are nine sizes available, ranging from 640x512 down to
160x128 pixels.

--------------------
| Grab | Line skip |
--------------------
This icon gives access to a writable icon, in which you may enter the 'line
skip' factor.

The line skip factor is the number of scanlines that will be skipped at the
top of the video image that is being digitised. A value of zero selects the
default line skip (an equal number of scanlines above and below the picture
is skipped). Any positive number may be entered, but, as a video image has a
limited number of scanlines, values that are too large may cause the resulting
image to be distorted.

----------------------
| Grab | Sensitivity |
----------------------
This icon leads to a slider bar in which the sensitivity of the podule to the
video signal may be changed from 0 (least sensitive) to 100% (most sensitive).

This icon is only available when a special chip is present on the podule
through which the sensitivity is controlled, instead of the potentiometer at
the back on the standard model. If this is not present, this icon is shaded.

-----------------------
| Grab | Video signal |
-----------------------
This icon gives access to a video signal window.

This window will graphically display the synchronisation signals present in
the video signal and enables strange or non-standard video signals to be
identified. A rough classification of the present video signal is given at
the bottom of the video signal window (usually 'No video signal' or 'Normal
video signal'). The signal represents the exclusive or of the vsync and hsync
signals.

Clicking a mouse button will abort the plotting.

----------
| Pop up |
----------
This icon leads to a submenu in which options may be set that influence the
way the image is first displayed when it is popped up in the image window,
or after a change of screen mode.

-------------------------
| Pop up | Auto palette |
-------------------------
Clicking on this icon toggles the 'auto palette' flag.

When ON (i.e. ticked), a greyscale palette is automatically selected (in fact,
its effect is exactly the same as clicking on the 'Grey palette' icon, refer
to its discussion for more details).

----------------------
| Pop up | Auto zoom |
----------------------
Clicking on this icon toggles the 'auto zoom' flag.

When ON (i.e. ticked), the image is automatically zoomed (see the discussion
of the zoom options elsewhere) so that it fits the screen well (i.e. is
fully visible).

-----------
| Process |
-----------
This icon leads to a submenu of processing options. There are several fast
image processing filters, and an option to switch on pixel-editing and cutting,
among others.

For more technical details on the image processing algorithms, refer to
'Technical details'.

--------------------
| Process | Invert |
--------------------
Clicking on this icon will 'invert' the image.

This means that the entire greyvalue scale from black to white is reversed,
thus producing a 'negative' image. Its effect may be reversed by using it
a second time.

--------------------
| Process | Filter |
--------------------
This icon gives access to a submenu in which several image filters may be
applied by clicking on their respective icons.

-----------------------------------
| Process | Filter | Noise (soft) |
-----------------------------------
This filter will remove noise from the image.

This is the 'soft' version of the noise removal filters, which generally does
not affect many pixels which are not 'noise pixels', but has the disadvantage
that it will usually not succeed in removing all the noise from an image
either.

-------------------------------------
| Process | Filter | Noise (strong) |
-------------------------------------
This filter, like the soft noise filter, will remove noise from the image.

This 'strong' version will (as its name suggests) remove more noise, but has
the disadvantage of possibly affecting much more pixels which aren't noise.

----------------------------
| Process | Filter | Gauss |
----------------------------
This 'lowpass' filter has the effect of 'smoothing' the image.

The smoothing effect is somewhat weaker than that of the Average filter. As a
'smoother', it also effectively removes noise from the image, but the noise
filters should be used by preference to do this, as a lot of image detail is
lost using smoothing filters.

------------------------------
| Process | Filter | Average |
------------------------------
This 'lowpass' filter is similar to the Gauss filter, but has a stronger
'smoothing' effect.

------------------------------
| Process | Filter | Laplace |
------------------------------
This 'highpass' filter will, in contrast to the Gauss and Average filters,
enhance detail in the image.

It has the effect of amplifying local image details, but frequently has the
side-effect of making the image look rather 'harsh'.

---------------------------------------
| Process | Filter | X-gradient Sobel |
---------------------------------------
This filter effectively has a kind of '3-D' effect on the image.

It reacts on horizontal 'gradients' in the image.

---------------------------------------
| Process | Filter | Y-gradient Sobel |
---------------------------------------
This filter is similar to the X-gradient Sobel filter, but reacts on vertical
'gradients' in the image.

------------------------------
| Process | Filter | Maximum |
------------------------------
This filter amplifies the presence of the peak greyvalues in the image.

------------------------------
| Process | Filter | Minimum |
------------------------------
This filter amplifies the presence of the lowest greyvalues in the image.

--------------------
| Process | Expand |
--------------------
Clicking on this icon will expand the greyvalue range of the image.

This algorithm determines the lowest and highest used greyvalues in the
image, and expands the range between these values to the full 0-255 range.
This increases the visual contrast of images that do not use the full
available greyscale range.

----------------------
| Process | Equalize |
----------------------
Clicking on this icon will perform 'histogram equalization' on the image.

This algorithm effectively measures the greyvalue contents of the image and
attempts to balance greyvalue use. It can have a dramatic enhancing effect
on some images. However, on low-contrast images it can have an equally
dramatic degrading effect (they become much lighter and more 'harsh').

------------------
| Process | Edit |
------------------
Clicking on this icon will toggle the 'edit' flag. It enables pixel editing
and cutting of the image.

When ON (i.e. ticked), the image may be edited using the mouse pointer.
While the mouse pointer is in the image window, its center will change to
the colour of the pixel underneath it, so it is easier to identify a
particular pixel among others.

Pixel editing
-------------
Pressing SELECT or ADJUST on a particular pixel enables you to remove noise
pixels by hand :

- SELECT will change the greyvalue of the pixel to the average greyvalue of
  its surrounding neighbors, i.e. it adds all eight surrounding pixels'
  greyvalues and assigns this value DIV 8 to the target pixel. This 'smooths
  out' noisy pixels which can thus be removed with accuracy by hand, in
  preference to using the noise or smoothing filters.
- ADJUST has a similar effect, except the target pixel's greyvalue itself
  is considered in the averaging, i.e. the eight surrounding pixels'
  greyvalues and the target pixel's greyvalue are added, and the resulting
  value DIV 9 is assigned to the target pixel. This is equivalent to what the
  'Average' filter does.

Cutting
-------
Pressing SELECT or ADJUST while holding down the SHIFT key enables you to
cut off the top/left or bottom/right parts of the image :

- SELECT will cut off the top/left part of the image : the pixel clicked on
  will become the new top left pixel
- ADJUST will cut off the bottom/right part of the image : the pixel clicked
  on will become the new bottom right pixel

NOTE : The zoom options may be used while editing, so it is very easy to
locate and 'kill' individual pixels, and perform precision cutting. The pixel
info window (see below) is useful as a further aid in precision cutting and
editing.

------------------------
| Process | Pixel info |
------------------------
Clicking on this icon will pop up the pixel info window.

When the edit flag is ON, this shows the coordinates and greyvalue of the
pixel at the mouse pointer. The top coordinates shown in the window are pixel
offsets from the top left of the image, while the bottom pair represents the
offsets from the bottom right of the image.

This information may help when, for example, cutting has to be very precise
(i.e. you know the number of pixels you want to cut off from the sides).

--------
| Zoom |
--------
This icon gives access to a submenu of zoom options. These can be used to
zoom in or out on the image. The current zoom factors are reflected in the
image window's title (if not 1:1).

-----------------
| Zoom | In/Out |
-----------------
These icons give access to zoom in and zoom out options respectively. Zooming
takes place in steps of 2 (i.e. 2 times, 4 times, 8 times enlarged/reduced,
etc.). By clicking one of the icons given in their submenu's, zooming can be
performed in x ('x') or y ('y') directions individually, or both at the same
time ('Both').

--------------
| Zoom | 1:1 |
--------------
Clicking this icon will reset the zoom factors to 1 (i.e. the image is neither
enlarged nor reduced).

--------
| Misc |
--------
This icon leads to a submenu with miscellaneous options.

-----------------------
| Misc | Grey palette |
-----------------------
Clicking on this icon will select a greyscale palette from black to white.

NOTE : In 256-colour modes, the palette remains unchanged, as it is not
possible to get more than 16 shades of grey by changing it. Refer to
'Displaying greyvalues' for more details.

---------------------
| Misc | Save Clear |
---------------------
This icon leads to a save file window, in which the image may be saved as
a Clear file by entering a (leaf) filename and dragging the filetype icon
to a directory viewer.

The Clear file saved will be 8-bit grey-scale.

Further processing (scale, rotate, mirror, Floyd-Steinberg dithering, etc.)
or conversion to other graphics formats may be performed by using my other
image processing applications Translator and Creator respectively. Refer to
the end of this guide for more details.

----------------------
| Misc | Save Sprite |
----------------------
This icon leads to a save file window, in which the image may be saved as
a Sprite file by entering a (leaf) filename and dragging the filetype icon
to a directory viewer.

The Sprite file saved will be 8-bit, with no palette (i.e. standard palette
actually). The greyvalues of the image are mapped (1-1) to the closest
colours in the standard 256-colour palette that represent them when the
sprite is displayed on a monochrome monitor.

--------------------
| Misc | Auto name |
--------------------
Clicking on this icon toggles the 'auto name' flag.

When ON, the leafnames for files to be saved are generated automatically
from a list that may be entered in the writable icon in the submenu. The
list consists of leafnames, seperated by comma's. The leafnames are taken
cyclically from this list, so 'R,G,B' generates 'R', then 'G', then 'B',
then 'R', then 'G', etc..

The current leafname is reset to the first in the list by :
- Switching 'Auto name' to ON
- Entering a new list in the writable icon

So, if, for any reason, you want to reset the current leafname to the first
one in the list, simply switch the 'auto name' flag off, then on again.


-------------------------
- Displaying greyvalues -
-------------------------
As the Archimedes can display only 16 shades of grey, it is not possible
to give a correct representation of the full 0-255 greyscale range of the
image, even in 256 colour modes.

In 16, 4 and 2 colour modes, a selection of the 16 available greys is made
to create a scale from black to white, and the full greyscale is simply mapped
to the closest of these greys.

In 256-colour modes (and when saving an image as a sprite), the full greyscale
of the image is mapped (1-1) to the colours of the standard 256-colour palette
which closely represent them when the sprite is being displayed on a monochrome
monitor (for example, using the mono video output on the back of the
Archimedes). This is the only way to get more shades of grey on-screen.

To get the best possible result on colour monitors (i.e. using a maximum of
16 shades of grey), save the image as a Clear file and use Translator's
Floyd-Steinberg dithering option (and the 'Current mode' and 'Greyscale'
palette settings when dithering to non-256 colour modes).


---------------------
- Technical details -
---------------------
- The GreyEdit module

The SWI's contained in the GreyEdit module may be useful to users that wish
to build their own image processing or digitizing applications. Refer to
the file Docs.SWIs for detailed descriptions.

- Image filters

The filters apply a 'local' filtering algorithm to the image. Most filters
are '3x3 local neighborhood' filters, which means that for every pixel in the
image, the surrounding eight pixels are considered, together with the current
value of the pixel, to compute a new pixel value according to the algorithm
used.

Most algorithms attach 'weights' to these 9 pixels and calculate the new
greyvalue by adding all (or some of) the pixel values, multiplied with these
weights, and then divide the result by the total weight to average it.

All these filters map any pixels lying 'outside' the image to the nearest
image pixel (i.e. this occurs for all target pixels at the 4 borders).

The individual filters are discussed below. The 'target' pixel is always
the 'middle' pixel, and these terms are used interchangably. The number of
pixels in the neighborhood of this 'middle' pixel that are considered depends
on the filter.

Noise (soft)
------------
If the pixel left to the target pixel is equal (in greyvalue) to the right
pixel, the middle pixel is replaced with the left (=right) pixel value.

Noise (strong)
--------------
If the target pixel is either the maximum or the minimum among the north,
south, east and west pixels, it is replaced with the average value of the
north, south, east and west pixels (this is usually called 'outlier pixel
removal' in image processing literature).

Gauss, lowpass filter
---------------------
The target pixel becomes the weighted average of the greyvalues of the
nw,n,ne, w,mid,e, sw,s,se pixels with corresponding weigths : 1,2,1,
2,4,2, 1,2,1 (i.e. the sum DIV 16 is calculated for the middle pixel).

Average, lowpass filter
-----------------------
Weighted average, all weights equal to 1 (i.e. result is sum DIV 9).

Laplace, highpass filter
------------------------
Weighted average, with weights 0,-1,0, -1,5,-1, 0,-1,0 (i.e. sum is
calculated, and a range check is done (<0 becomes 0, >255 becomes 255)).

Grad-x Sobel, highpass filter
-----------------------------
Weighted average, with weights -1,0,1, -2,0,2, -1,0,1 (i.e. sum is calculated,
127 is added, and a range check is done (<0 is 0, >255 is 255)).

Grad-y Sobel, highpass filter
-----------------------------
Weighted average, with weights -1,-2,-1, 0,0,0, 1,2,1 (calculation as under
Grad-x Sobel filter).

Maximum
-------
The middle pixel becomes the maximum value of all nine pixels.

Minimum
-------
The middle pixel becomes the minimum value of all nine pixels.

- Histogram equalization

First, a 'cumulative histogram' is calculated that contains the cumulative
frequencies of the greyvalues in the entire range (i.e. the cumulative value
of greyvalue 255 is always equal to the total number of pixels in the image).

The cumulative histogram is then scaled down and used as a transformation
factor table to map the old greyvalue range to the full 0-255 greyvalue range.
This yields a new cumulative histogram graph that is as 'flat' as possible,
i.e. the greyvalue content of the image has been 'balanced'.


----------------
- Memory usage -
----------------
GreyEdit automatically grabs the memory it needs to load/grab an image,
and releases it again when the image is discarded (i.e. the image window
is closed or a new image is loaded/grabbed) or cut down.

This ensures that it always runs in the minimum amount of memory and that
you don't need to worry about how much memory to allocate to it. Users
of 1Mb machines will appreciate this scheme, which enables larger images
to be handled without trouble when multitasking with other applications.


------------------------
- Translator & Creator -
------------------------
These applications, which were also written by me, are essential companions
to GreyEdit.

Translator reads a very large number of (mainly foreign) graphics formats,
and can perform colour processing, dithering, scaling, rotate, etc.. It
outputs either sprite or Clear files. All graphic formats accepted by
Translator may be converted to grey-scale Clear files (to be used as input
for GreyEdit) by using the 'Black and white' and Clear output options.

Creator creates a number of (mainly foreign) graphics formats, accepting
Clear files and sprite files as input. It can create GIF, TIFF, AIM and
PBMPlus formats at present. This enables you to port images to a large
number of other computer platforms.

Translator and Creator are available from the address mentioned below and
are part of my shareware image processing package.


-----------
- The end -
-----------
This application is Shareware, and part of the image processing package
consisting of !Translator, !Creator and !GreyEdit.

I have put a lot of effort and time into these programs. Therefore, if you
find them useful, I kindly ask you to register yourself as a user of these
programs. The registration fee is just ú10 (ten english pounds).

Registration entitles you to free new versions of all the above mentioned
applications when they become available, and improved support (and willingness
to add special features). You will also give me an incentive to continue
producing good software for the Archimedes, and keep on improving my existing
applications.

If you want to register, or if you have praise, complaints, comments, bugs(!),
or anything else to offer me, do not hesitate to write to

John Kortink
Middelhuisstr. 17
7482 EL Haaksbergen
The Netherlands

or send email to [e-mail]

Important note : If you want Translator or Creator to handle a new format,
always send me full information, and several example files.

New versions of the applications are available from the same address : just
send ú1 to cover postage and a self-addressed envelope containing a 3.5" disc.
As the applications are under continuous development, it is likely that you
will get a more recent version.

NOTE : To register AND receive the latest versions of the applications, send
ú11 in total, and don't forget the self-addressed envelope and disc.

Happy imaging !!!

_______________________________________________________________________________

!!! NOTE !!!

You may NOT change this application or use ANY part of it in other products
without my approval. You may spread it freely (with *ALL* files included), but
not for any profit. This software is provided 'as is'. Using it is entirely at
your own risk.

_______________________________________________________________________________