                                I t s a g i f
                                 M a n u a l                      

This is a very brief manual for itsagif. A larger manual may be found
online at http://www.cafe.net/peda/iag/man.html.

The program begins with a splash screen. You can dismiss the splash screen
by pressing a key or button; itsagif then asks for a PICT file to open.
After a file is chosen, itsagif will display an image preview and a control
window, both of which are named after the chosen file.  Opening a file
named "Example" will result in the following control window:

            (images are available in the online manual)

We will now go over each element of the control window, from top to bottom.      

   Source Controls      

   The source controls display information about the source image.

Size: 199x204 (159K)          
   This control displays the size of the original image. Our example
   image is 199 pixels wide and 204 pixels high. When placing the GIF file
   in some HTML the size should be included. For our example, the
   appropriate HTML would be "<img src="Example.gif" width=199 height=204>".

   The memory requirements are listed after the image dimensions. Our
   example image uses 159K when stored as a 24-bit image without any
   compression.
   
2254 colours
   This control displays the number of colours present in the original image; 
   our example image has 2254 distinct colours.      
   
Destination Controls      
   The destination controls determine how the image is converted into a GIF
   image.

Size: 199x205 (71.9K)
   This control displays the size of the produced image; the dimensions of
   the produced image match those of the original image. However, the
   produced image will be a 71.9K GIF file. The GIF file will be identical
   to the preview image if you are previewing the image with a 24-bit video
   card. If you are previewing the image with a 1,2,4,8, or 16-bit video
   card the produced GIF file will be as good or better than the preview
   image.
   
   The remaining destination controls impact the quality and memory
   requirements of the produced GIF file. After changing any of the
   controls, itsagif will automatically recompute the preview image and
   memory requirements. While computing the memory requirements itsagif may
   display lower estimates of the size (for example ">36K"...">44K"...
   ...">60K"..."71.9K").

2254 colours
   This control displays the number of colours used in the produced image.
   You may specify the number of colours by entering a value into this
   control. Using fewer colours will usually reduce the size of the produced
   GIF file.

9 passes
   This control displays the number of passes needed to render the image.
   Each pass can paint at most 256 colours. You may specify the number of
   passes by entering a value into this control. Using fewer passes will
   usually reduce the size of the produced GIF file.

First pass: 256 colours
   This control displays the number of colours used to paint the first pass.          
   Using a small number of colours on the first pass allows viewers to get a
   quick preview of image. To see what the image will look like after the
   first pass, set this control as desired and subsequently specify that one
   pass is to be used to render the image (using the # of passes control
   described above). You will also see the memory size of the first pass;
   14,400 baud modems transfer approximately 1K per second.

Later passes: 255 colours
   This control displays the number of colours used to paint all passes after          
   the first pass.

Background (FFFFFF)
   This control displays a small swatch of colour that represents the image's
   intended background colour along with the HTML description of that colour.
   Clicking on the colour allows you to choose a new colour; option-clicking
   gives you finer control over the colour chosen. Our example image has a
   white background (the default) which is specified in HTML as
   "bgcolor=#FFFFFF" in the body tag, as follows: "<body bgcolor=#FFFFFF>".
   Itsagif will display the background colour around the preview image as
   well as over portions of the image that have been marked as transparent.

Transparency
   When this control is checked, portions of the image are transparent. To
   specify a transparent colour, move the pointer over the desired colour on
   the preview image and click once. Click over other colours to specify
   multiple transparency colours. Clicking over a transparent region causes
   the underlying colour to become opaque again. the delete key removes
   the most recently added transparency colour.
   
   Unchecking this control will disable transparency.

Interlace first pass
   When this control is checked, the first pass of the image will be stored
   in an interlaced manner. Interlacing the first pass allows viewers to
   get a very quick idea of what the image will look like as it is being
   downloaded. Interlacing usually increases the memory size, although only
   slightly.
   
Interlace later passes
   When this control is checked, all passes after the first pass are
   interlaced. Most browsers will present the image to the viewer in less
   time if later passes are not interlaced.                                      
   
Use global colour table
   When this control is checked, a single colour table is used for all
   passes, instead of one colour table per pass. Images with a global
   colour table are compatible wuth more (older) browsers and utilities.
   Multiple passes may still be used to provide sharp previews.

          *                         *                            *

Be warned that itsagif requires *alot* of memory for larger continuous-tone
images, as it keeps both the original and preview image in memory at 24-bits.
Furthermore, additional structures are used to maintain exact knowledge
about every colour in the image. Large continuous-tone images take a *long*
time to load, as these structures are built up as the image is loaded. The
algorithms may be improved in the future, if there is enough demand - the
program was written mainly out of interest and to demonstrate that GIF files
can contain more than 256 colours.

____________________________________
(1) The Graphics Interchange Format(C) is the Copyright property of
CompuServeIncorporated. GIF(sm) is a service mark property of CompuServe
Incorporated.
