                            ST Picture Formats
                            ------------------
                                Edited by:
 
                               David Baggett
                          5640 Vantage Point Road
                          Columbia, MD  21044 USA
                              (301)  596-4779    
 
                                 Internet:
                              dmb@wam.umd.edu 
                                dmb@tis.com
 
                    (Please report errors or additions.)
 
         Copyright (C) 1988, 1989, 1990, 1991 by David M. Baggett
 
 
     Non-profit redistribution of this document is permitted, provided
     the document is not modified in any way.
 
     Reproduction of this document in whole or in part for  commercial
     purposes is expressly forbidden without the prior written consent
     of David M. Baggett.
 
     The  information  presented here is not guaranteed to be correct.
     The editor and contributors will in no event be liable for direct,
     indirect, incidental, or consequential damages resulting from the 
     use of the information in this document.
 
     This document is the product of many hours of volunteer work by a
     large number of people. Please respect this -- do not violate the
     distribution policy.
 
 
                               CONTRIBUTORS
   
     Steve Belczyk  Phil Blanchfield  Jason Blochowiak  John Brochu**
         David Brooks  Daniel Deimert  Neil Forsyth  Stefan Hoehn  
     Gerfried Klein  G. "Maddog" Knauss  Ken MacLeod  Shamus McBride
          Jim McCabe  Lars Michael  Darek Mihocka  David Mumper
            George Nassas  Jim Omura  George Seto  Joe Smith
               Greg Wageman  Roland Waldi*  Gerry Wheeler
 
 
                                 Contents 
                                 --------
 
         NEOchrome                               *.NEO
         NEOchrome Animation                     *.ANI
         DEGAS                                   *.PI?   ? = 1, 2, 3
         DEGAS Elite                             *.PI?   ? = 1, 2, 3
         DEGAS Elite (Compressed)                *.PC?   ? = 1, 2, 3
         Tiny                                    *.TN?   ? = 1, 2, 3, Y
         Spectrum 512                            *.SPU
         Spectrum 512 (Compressed)               *.SPC
         Spectrum 512 (Smooshed)                 *.SPS
         Art Director                            *.ART
         C.O.L.R. Object Editor Mural            *.MUR
         Doodle                                  *.DOO
         Cyber Paint Sequence                    *.SEQ
         Animatic Film                           *.FLM
         Animaster Sprite Bank                   *.ASB
         STOS                                    *.MBK
         GEM Bit Image                           *.IMG
         STAD                                    *.PAC
         Imagic Film/Picture                     *.IC?   ? = 1, 2, 3
         IFF                                     *.IFF
         RGB Intermediate Format                 *.RGB
         ComputerEyes Raw Data Format            *.CE?   ? = 1, 2
         MacPaint                                *.MAC
         PackBits Compression Algorithm
  
 
                         Introductory Information
                         ------------------------
 word    = 2 bytes
 long    = 4 bytes
 palette = Hardware color palette, stored as 16 words.  First word is
           color register zero (background), last word is color register
           15.  Each word has the form:
 
           Bit:  (MSB) 15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00 (LSB)
                       -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
                        0  0  0  0  0 R2 R1 R0  0 G2 G1 G0  0 B2 B1 B0
 
           R2 = MSB of red intensity
           R0 = LSB of red intensity
 
           G2 = MSB of green intensity
           G0 = LSB of green intensity
 
           B2 = MSB of blue intensity
           B0 = LSB of blue intensity
 
           Intensity ranges from 0 (color not present) to 7 (highest
           intensity).
 
           Example: { red = 7, green = 3, blue = 5 } -> 0735 (hex)
 
           Caveat:  It is wise to mask off the upper four bits of each
                    palette entry, since a few programs store special
                    information there (most notably Art Studio).
 
 
                              The Formats
                              -----------
 
 <NEOchrome>     *.NEO
  
 1 word          flag byte [always 0]
 1 word          resolution [0 = low res, 1 = medium res, 2 = high res]
 16 words        palette
 12 bytes        filename [usually "        .   "]
 1 word          color animation limits.  High bit (bit 15) set if color
                 animation data is valid.  Low byte contains color animation
                 limits (4 most significant bits are left/lower limit,
                 4 least significant bits are right/upper limit).
 1 word          color animation speed and direction.  High bit (bit 15) set
                 if animation is on.  Low order byte is # vblanks per step.
                 If negative, scroll is left (decreasing).  Number of vblanks
                 between cycles is |x| - 1
 1 word          # of color steps (as defined in previous word) to display
                 picture before going to the next.  (For use in slide shows)
 1 word          image X offset [unused, always 0]
 1 word          image Y offset [unused, always 0]
 1 word          image width [unused, always 320]
 1 word          image height [unused, always 200]
 33 words        reserved for future expansion
 16000 words     picture data (screen memory)
 -----------
 32128 bytes     total
  
 
 <NEOchrome Animation>        *.ANI
 
 NOTE:      To get this feature on versions 0.9 and later select the Grabber
            icon and click both mouse buttons in the eye of the second R in the
            word GRABBER.
            Interestingly enough, some versions of NEO only require you
           to press the right button, not both.  Hmmm...
 
 1 long          magic number BABEEBEA (hex) (seems to be ignored)
 1 word          width of image in bytes (always divisible by 8)
 1 word          height of image in scan lines
 1 word          size of image in bytes + 10 (!)
 1 word          x coordinate of image (must be divisible by 16) - 1
 1 word          y coordinate of image - 1
 1 word          number of frames
 1 word          animation speed (# vblanks to delay between frames)
 1 long          reserved; should be zero
 --------
 22 bytes        total for header
 
 ? words         image data (words of screen memory) for each frame, in 
                 order
 
 
 <DEGAS>         *.PI1 (low resolution)
                 *.PI2 (medium resolution)
                 *.PI3 (high resolution)
 
 1 word          resolution (0 = low res, 1 = medium res, 2 = high res)
                 Other bits may be used in the future; use a simple bit
                 test rather than checking for specific word values.
 16 words        palette
 16000 words     picture data (screen memory)
 -----------
 32034 bytes     total
 
 
 <DEGAS Elite>   *.PI1 (low resolution)
                 *.PI2 (medium resolution)
                 *.PI3 (high resolution)
 
 1 word          resolution (0 = low res, 1 = medium res, 2 = high res)
                 Other bits may be used in the future; use a simple bit
                 test rather than checking for specific word values.
 16 words        palette
 16000 words     picture data (screen memory)
 4 words         left color animtion limit table (starting color numbers)
 4 words         right color animation limit table (ending color numbers)
 4 words         animation channel direction flag (0 = left, 1 = off, 2 = right)
 4 words         128 - animation channel delay in 1/60's of a second. [0 - 128]
                 (I.e., subtract word from 128 to get 1/60th's of a second.)
 -----------
 32066 bytes     total
 
 
 <DEGAS Elite (Compressed)>      *.PC1 (low resolution)
                                 *.PC2 (medium resolution)
                                 *.PC3 (high resolution)
  
 1 word          resolution (same as Degas, but high order bit is set;
                 i.e., hex 8000 = low res, hex 8001 = medium res,
                 hex 8002 = high res).  Other bits may be used in the
                 future; use a simple bit test rather than checking
                 for specific word values.
 16 words        palette
 < 32000 bytes   control/data bytes
 4 words         left color animation limit table (starting color numbers)
 4 words         right color animation limit table (ending color numbers)
 4 words         animation channel direction flag [0 = left, 1 = off, 2 = right]
 4 words         128 - animation channel delay in 1/60's of a second. [0 - 128]
                 (I.e., subtract word from 128 to get 1/60th's of a second.)
 -----------
 < 32066 bytes   total
  
 Compression Scheme:
  
    PackBits compression is used (see below).  Each scan line is compressed
 separately; i.e., all data for a given scan line appears before any data
 for the next scan line.  The scan lines are specified from top to bottom
 (i.e., 0 is first).  For each scan line, all the data for a given bit plane
 appears before any data for the next higher order bit plane.  Note that this
 is identical to the IFF 'BODY' image data.
    To clarify:  The first data in the file will be the data for the lowest
 order bit plane of scan line zero, followed by the data for the next higher
 order bit plane of scan line zero, etc., until all bit planes have been
 specified for scan line zero.  The next data in the file will be the data
 for the lowest order bit plane of scan line one, followed by the data for
 the next higher order bit plane of scan line one, etc., until all bit planes
 have been specified for all scan lines.
  
 Caveats:
  
    DEGAS Elite's picture loading routine places some restrictions on
 compressed DEGAS files:
  
         o Elite uses a 40-byte buffer to store data being decompressed.
  
         o Whenever a control command is encountered, bytes are stuffed
         in this buffer.
  
         o The buffer is only emptied when there are EXACTLY 40
         characters in it.
  
 The important conclusion here is that
  
         No control command may cause the buffer to have more than 40
         bytes in it.  In other words, all control commands must end on
         or before the 40-byte boundary.
  
 Any picture violating the last condition will cause Elite to get a bus
 error when the picture is loaded.
  
 
 <Tiny>  *.TNY (any resolution)
         *.TN1 (low resolution)
         *.TN2 (medium resolution)
         *.TN3 (high resolution)
 
    Several people have reported sightings of mutated Tiny pictures that
 do not follow the standard format, so let's be careful out there.  What
 is described here is the format that David Mumper's original
 TNYSTUFF.PRG produces.
 
 1 byte          resolution (same as NEO, but +3 indicates rotation
                 information also follows)
 
 If resolution > 2 {
 1 byte          left and right color animation limits.  High 4 bits
                 hold left (start) limit; low 4 bits hold right (end) limit
 1 byte          direction and speed of color animation (negative value
                 indicates left, positive indicates right, absolute value
                 is delay in 1/60's of a second.
 1 word          color rotation duration (number of iterations)
 }
 
 16 words        palette
 1 word          number of control bytes
 1 word          number of data words
 3-10667 bytes   control bytes
 1-16000 words   data words
 -------------
 42-32044 bytes  total
 
 Control byte meanings:
 
         For a given control byte, x:
 
         x < 0   Absolute value specifies the number of unique words to
                 take from the data section (from 1 to 127)
         x = 0   1 word is taken from the control section which specifies
                 the number of times to repeat the next data word (from
                 128 to 32767)
         x = 1   1 word is taken from the control section which specifies
                 the number of unique words to be taken from the data
                 section (from 128 - 32767)
         x > 1   Specifies the number of times to repeat the next word
                 taken from the data section (from 2 to 127)
 
 Format of expanded data:
 
    The expanded data is not simply screen memory bitmap data; instead, the 
 data is divided into four sets of vertical columns.  (This results in
 better compression.)  A column consists of one specific word taken
 from each scan line, going from top to bottom.  For example, column 1 
 consists of word 1 on scanline 1 followed by word 1 on scanline 2, etc., 
 followed by word 1 on scanline 200.
    The columns appear in the following order:
 
    1st set contains columns 1, 5,  9, 13, ..., 69, 73, 77 in order
    2nd set contains columns 2, 6, 10, 14, ..., 70, 74, 78 in order
    3rd set contains columns 3, 7, 11, 15, ..., 71, 75, 79 in order
    4th set contains columns 4, 8, 12, 16, ..., 72, 76, 80 in order
 
 Note that Tiny partitions the screen this way regardless of resolution; i.e., 
 these aren't bitplanes.  For example, medium resoltion only has two bitplanes, 
 but Tiny still divides medium resolution pictures into four parts.
 
 
 <Spectrum 512>  *.SPU
 
 80 words        first scan line of picture (unused) -- should be zeroes
 15920 words     picture data (screen memory) for scan lines 1 through 199
 9552 words      3 palettes for each scan line (the top scan line is
                 not included because Spectrum 512 can't display it)
 -----------
 51104 bytes     total
 
 Note that the Spectrum 512 mode's three palette changes per scan
 line allow more colors on the screen than normally possible, but a
 tremendous amount of CPU time is required to maintain the image.
 
 The Spectrum format specifies a palette of 48 colors for each scan line.
 To decode a Spectrum picture, one must be know which of these 48 colors
 are in effect for a given horizontal pixel position.
 
 Given an x-coordinate (from 0 to 319) and a color index (from 0 to 15),
 the following C function will return the proper index into the Spectrum
 palette (from 0 to 47):
 
 /*
  *  Given an x-coordinate and a color index, returns the corresponding
  *  Spectrum palette index.
  *
  *  by Steve Belczyk; placed in the public domain December, 1990.
  */
 int 
 FindIndex(x, c)
         int x, c;
 {
         int x1;
 
         x1 = 10 * c;
 
         if (1 & c)              /* If c is odd */
                 x1 = x1 - 5;
         else                    /* If c is even */
                 x1 = x1 + 1;
          if (x >= x1 && x < x1 + 160) 
                 c = c + 16;
         else if (x >= x1 + 160) 
                 c = c + 32;
 
         return c;
 }
 
 
 <Spectrum 512 (Compressed)>        *.SPC
  
 1 word          flag word [$5350 or "SP"]
 1 word          reserved for future use [always 0]
 1 long          length of data bit map
 1 long          length of color bit map
 <= 32092 bytes  compressed data bit map
 <= 17910 bytes  compressed color bit map
 --------------
 <= 50014 bytes  total
  
 Data compression:
  
    Compression is via a modified run length encoding (RLE) scheme,
 similar to DEGAS compressed and Tiny.  The data map is stored as a
 sequence of records.  Each record consists of a header byte followed by
 one or more data bytes.  The meaning of the header byte is as follows:
  
         For a given header byte, x:
  
            0 <= x <= 127   Use the next x + 1 bytes literally (no repetition)
         -128 <= x <=  -1   Use the next byte -x + 2 times

 The data appears in the following order:
  
         1. Picture data, bit plane 0, scan lines 1 - 199
         2. Picture data, bit plane 1, scan lines 1 - 199
         3. Picture data, bit plane 2, scan lines 1 - 199
         4. Picture data, bit plane 3, scan lines 1 - 199
  
 Decompression of data ends when 31840 data bytes have been used.
  
 Color map compression:
  
    Each 16-word palette is compressed separately.  There are three
 palettes for each scan line (597 total).  The color map is stored as a
 sequence of records.  Each record starts with a 1-word bit vector which
 specifies which of the 16 palette entries are included in the data
 following the bit vector (1 = included, 0 = not included).  If a palette
 entry is not included, it is assumed to be zero (black).  The least
 significant bit of the bit vector refers to palette entry zero, while the
 most significant bit refers to palette entry 15.  Bit 15 must be zero,
 since Spectrum 512 does not use palette entry 15.  Bit 0 should also be
 zero, since Spectrum 512 always makes the background color black.
    The words specifying the values for the palette entries indicated in
 the bit vector follow the bit vector itself, in order (0 - 15).
 
 NOTE:   Regarding Spectrum pictures, Shamus McBride reports the following:
 
         "... [The Picture Formats List] says bit 15 of the color map vector
         must be zero. I've encountered quite a few files where [bit 15] is 
         set (with no associated palette entry)..."
 
 
 <Spectrum 512 (Smooshed)>          *.SPS
 
    This format compresses Spectrum 512 pictures better than the standard
 method.  There are at least two programs that support this format, SPSLIDEX
 and ANISPEC, although the two seem to differ slightly in their interpretation
 of the format.
    One point of interest: Shamus McBride deciphered this format without an ST!
  
 1 word          5350 (hex) ("SP")
 1 word          0 (reserved for future use)
 1 long          length of data bit map
 1 long          length of color bit map
 <= ? bytes      compressed data bit map
 <= ? bytes      compressed color bit map
 ----------
 < ?  bytes      total
 
 Data compression:
 
    Compression is via a modified run length encoding (RLE) scheme,
 similar to that used in Spectrum Compressed (*.SPC) pictures.
 
 The data map is stored as a sequence of records.  Each record consists of a
 header byte followed by one or more data bytes.  The meaning of the header
 byte is as follows:
 
         For a given header byte, x (unsigned):
 
           0 <= x <= 127    Use the next byte x + 3 times
         128 <= x <= 255    Use the next x - 128 + 1 bytes literally
                            (no repetition)
 
 There are two kinds of *.SPS files.
 
 The data may appear in the same order as *.SPC files (SPSLIDEX format?):
 
         1. Picture data, bit plane 0, scan lines 1 - 199
         2. Picture data, bit plane 1, scan lines 1 - 199
         3. Picture data, bit plane 2, scan lines 1 - 199
         4. Picture data, bit plane 3, scan lines 1 - 199
 
 The second variant (ANISPEC format?) encodes the data as byte wide vertical
 strips:
 
         Picture data, bit plane 0, scan line   1, columns   0 -   7.
         Picture data, bit plane 0, scan line   2, columns   0 -   7.
         Picture data, bit plane 0, scan line   3, columns   0 -   7.
         . . .
         Picture data, bit plane 0, scan line 199, columns   0 -   7.
         Picture data, bit plane 0, scan line   1, columns   8 -  15.
         Picture data, bit plane 0, scan line   2, columns   8 -  15.
         . . .
         Picture data, bit plane 0, scan line 199, columns 312 - 319.
         Picture data, bit plane 1, scan line   1, columns   0 -   7.
         . . .
         Picture data, bit plane 3, scan line 198, columns 312 - 319
         Picture data, bit plane 3, scan line 199, columns 312 - 319.
 
 A for loop to process that data would look like
 
         for (plane = 0; plane < 4; plane++)
             for (x = 0; x < 320; x += 8)
                 for (y = 1; y < 200; y++)
                     for (x1 = 0; x1 < 8; x1++)
                         image[y, x + x1] = ...
 
 Color map compression:
 
    Color map compression is similar to *.SPC color map compression, but
 the map is compressed as a string of bits, rather than words.  There are
 597 records (one for each palette). Each record is composed of a 14-bit
 header followed by a number of 9-bit palette entries.  The 14-bit header
 specifies which palette entries follow (1 = included, 0 = not included).
 The most significant bit of the header refers to palette entry 1, while
 the least significant bit refers to palette 14.  Palette entries 0 and 15
 are forced to black (zero).  Each palette entry is encoded as "rrrgggbbb".
 
 The format of the palette is described above in the section on uncompressed
 Spectrum pictures (*.SPU).
 
 
 <Art Director>  *.ART (low resolution only)
 
 16000 words     picture data (screen memory)
 16 words        palette
 15 * 16 words   15 more palettes for animation
 -------------
 32512 bytes     total
 
 
 <C.O.L.R. Object Editor Mural>        *.MUR (low resolution only)
 
 16000 words     picture data (screen memory)
                 (palettes are stored in separate files)
 -----------
 32000 bytes     total
 
 
 <Doodle>        *.DOO (high resolution only)
 
 16000 words     picture data (screen memory)
 -----------
 32000 bytes     total
 
 
 <Cyber Paint Sequence>  *.SEQ (low resolution only)
 
    This format, while fairly complex, yields excellent compression of animated
 images while offering reasonably fast decompression times.
  
 1 word          magic number [$FEDB or $FEDC]
 1 word          version number
 1 long          number of frames
 1 word          speed (high byte is vblanks per frame)
 118 bytes       reserved
 ---------
 128 bytes       total for .SEQ header
 
 for each frame {
 1 word          type (ignored?)
 1 word          resolution [always 0]
 16 words        palette
 12 bytes        filename [usually "        .   "]
 1 word          color animation limits [not used]
 1 word          color animation speed and direction [not used]
 1 word          number of color steps [not used]
 1 word          x offset for this frame [0 - 319]
 1 word          y offset for this frame [0 - 199]
 1 word          width of this frame, in pixels (may be 0, see below)
 1 word          height of this frame, in pixels (may be 0, see below)
 1 byte          operation [0 = copy, 1 = exclusive or]
 1 byte          storage method [0 = uncompressed, 1 = compressed]
 1 long          length of data in bytes (if the data is compressed, this
                 will be the size of the compressed data BEFORE decompression)
 60 bytes        reserved                
 --------
 128 bytes       total for frame header
 
 ? bytes         data
 }
 
    Frames are "delta-compressed," meaning that only the changes from one
 frame to the next are stored.  On the ST, .SEQ files are always full-screen
 low resolution animations, so the sequence resulting from expanding all the
 data will be n 320 by 200 pixel low resolution screens, where n is given in
 the .SEQ header.
   
    Since only the changes from frame to frame are stored, image data for a
  frame will rarely be 320x200 (except for the very first frame, which will 
 always be a full screen).  Instead what is stored is the smallest rectangular
 region on the screen that contains all the changes from the previous frame to
 the current frame.  The x offset and y offset in the frame header determine
 where the upper left corner of the "change box" lies, and the width and height
 specify the box's size.
 
    Additionally, each "change box" is stored in one of five ways.  For each
    of these, the screen is assumed to have the full-screen image from the last
    frame on it.
    
    o uncompressed copy:  The data for this frame is uncompressed image data,
      and is simply copied onto the screen at position (x, y) specified
      in the frame header.
 
    o uncompressed eor:  The data for this frame is exclusive or'ed with the
      screen at position (x, y).
 
    o compressed copy:  The data for this frame must be decompressed (see 
      below), and then copied onto the screen at position (x, y) specified
      in the frame header.
  
    o compressed eor:  The data for this frame must be decompressed (see 
      below), and then exclusive or'ed with the screen RAM at position (x, y).
  
    o null frame:  The width and/or height of this frame is 0, so this
      frame is the same as the previous frame.
    
    Of the 5 methods above, the one that results in the smallest amount
    of data being stored for a particular is used for that frame.
   
 Compression Scheme:
 
    Compression is similar to that employed by Tiny, but is not quite as
 space-efficient.
 
 Control word meanings:
 
         For a given control word, x:
 
         x < 0   Absolute value specifies the number of unique words to
                 take from the data section (from 1 to 32767).
         x > 0   Specifies the number of times to repeat the next word
                 taken from the data section (from 1 to 32767).
 
         Note that a control word of 0 is possible but meaningless.
 
 Format of expanded data:
 
    The expanded data is not simply screen memory bitmap data; instead the four
 bitplanes are separated, and the data within each bitplane is presented
 vertically instead of horizontally.  (This results in better compression.)
 
    To clarify, data for a full screen would appear in the following order:
    
    bitplane 0, word 0, scanline 0
    bitplane 0, word 0, scanline 1
    ...
    bitplane 0, word 0, scanline 199
    bitplane 0, word 1, scanline 0
    bitplane 0, word 1, scanline 1
    ...
    bitplane 0, word 1, scanline 199
    ... 
    bitplane 0, word 79, scanline 199
    bitplane 1, word 0, scanline 0
    ... 
    bitplane 3, word 79, scanline 199
 
 Note however, that the data does not usually refer to an entire screen, but
 rather to the smaller "change box," whose size is given in the frame header.
 
 
 <Animatic Film> *.FLM (low resolution only)
 
 1 word          number of frames
 16 words        palette
 1 word          speed (0 - 99; value is 99 - # vblanks to delay between frames)
 1 word          direction (0 = forwards, 1 = backwards)
 1 word          end action (what to do after the last frame)
                 0 = pause, then repeat from beginning
                 1 = immediately repeat from beginning
                 2 = reverse (change direction)
 1 word          width of film in pixels
 1 word          height of film in pixels
 1 word          Animatic version number (major) [< 2]
 1 word          Animatic version number (minor)
 1 long          magic number 27182818 (hex)
 3 longs         reserved for expansion (should be all zeros)
 --------
 32 words        total for header
 
 ? words         image data (words of screen memory) for each frame, in order
 
 
 <Animaster Sprite Bank> *.ASB (low resolution only)
 
 1 word          number of frames - 1
 1 word          ?
 1 byte          maximum width, in pixels
 1 byte          maximum height, in pixels
 16 words        palette
 --------
 38 bytes        total for header
 
 For each frame {
 1 word          width of this frame (in pixels) - 1
 1 word          height of this frame (in pixels) - 1
 1 word          ? 
 ? words         image data (words of screen memory)
 }
 
 
 <STOS>  *.MBK
 
 9 words         ?
 1 long          $19861987 (magic number?)
 1 long          offset from this long to header for low resolution 
                 parameter block (if past end of file, no low res frames)
 1 long          offset from this long to header for med resolution 
                 parameter block (if past end of file, no med res frames)
 1 long          offset from this long to header for high resolution 
                 parameter block (if past end of file, no high res frames)
 1 word          number of low resolution frames
 1 word          number of medium resolution frames
 1 word          number of high resolution frames
 
 For each frame {
 1 long          offset to data (probably only used internally by STOS)
 1 byte          width in words (multiply by 16 to get width in pixels)
 1 byte          height in pixels
 1 byte          X hotspot location
 1 byte          Y hotspot location
 }
 
 (The format implies other stuff could be here.)
 
 1 long          ["PALT" $50414C54]
 16 words        palette
 
 ?               words of data for each frame, in the order mentioned in the
                 header.  Monoplanar mask data follows image data for each
                 frame.

 ----------
 ? words         total
 
    The frames often seem to be in semi-random order, not necessarily in 
 the order they are to be animated. 
 
 
 <GEM Bit Image> *.IMG
  
 1 word          version number of image file [1]
 1 word          length of header in words [usually 8]
 1 word          number of color planes [1 for monochrome]
 1 word          pattern length in bytes [1-8, usually 2 for screen images]
 1 word          pixel width in microns (1/1000 mm, 25400 microns per inch)
 1 word          pixel height in microns
 1 word          line width in pixels
 1 word          number of lines
 -------
 ? words         header length defined in 2nd word of header
  
 ? bytes         data
  
 NOTES:  If the image is a color image (planes > 1), the planes are stored
 separately starting with plane 0.  There is, however, no standard way of
 storing the color palette.  Some programs may save the palette in separate
 files, some may extend the header.  For this reason, you should never
 assume the header is 8 words long, always get the header length from the
 2nd word of the header.  Also, the line width in the 7th word is the number
 of pixels in a line.  Since the data is encoded in byte-wide packets, the
 actual unpacked line width is always a multiple of 8, and may be 1-7 pixels
 longer than the length specified in the header.
 
 For each byte x in the data section,
  
         x = 0           Pattern/scanline run.
                         Read the next byte, n (unsigned).
  
                         If n > 0 then:
                                 Read a number of bytes equal to the "pattern
                                 length" word in the header.  Repeat this
                                 pattern n times.
  
                         If n = 0 then:
                                 Scanline run.  Data for the next scanline
                                 is to be used multiple times.  Read the
                                 following record:
  
                                 1 byte          flag byte [$FF]
                                 1 byte          number of times to use
                                                 next scanline data
  
                                 The data for the next scanline follows,
                                 compressed normally.
  
         x = 80 (hex)    Uncompressed bit string.  The next byte
                         determines the number of bytes to use
                         literally.  The literal data bytes follow.
  
         otherwise       Solid run.  The value of x determines
                         what to draw.  The high bit specifies whether
                         the pixels are set or cleared.  A 1 indicates
                         a byte-run using $FF, a 0 indicates a byte-run
                         using $00.  The low 7 bits, taken as an unsigned
                         quantity, specify the length of the run in bytes.
  
 
 <STAD>          *.PAC (high resolution only)
 
 4 bytes         "pM86" (vertically packed) or "pM85" (horizontally packed)
 1 byte          id byte
 1 byte          pack byte (most frequently occuring byte in bitmap)
 1 byte          "special" byte
 -------
 7 bytes         total for header
 
 ? bytes         data
 
 The data is encoded as follows.  For each byte x in the data section:
 
         x = id byte             Read one more byte, n.  Use pack byte 
                                 n + 1 times.
         x = "special" byte      Read two more bytes, d, and n (in order).
                                 Use byte d n times.
         otherwise               Use byte x literally.
 
 
 <Imagic Film/Picture>           *.IC1 (low resolution)
                                 *.IC2 (medium resolution)
                                 *.IC3 (high resolution)
 
 4 bytes         "IMDC"
 1 word          resolution (0 = low res, 1 = medium res, 2 = high res)
 16 words        palette
 1 word          date (GEMDOS format)
 1 word          time (GEMDOS format)
 8 bytes         name of base picture file (for delta compression), or zeroes
 1 word          length of data (?)
 1 long          registration number
 8 bytes         reserved
 1 byte          compressed? (0 = no, 1 = yes)
 
 If compressed {
 1 byte          delta-compressed? (-1 = no, > -1 = yes)
 1 byte          ?
 1 byte          escape byte
 }
 -------
 65 bytes        total for header (68 bytes if compressed)
 
 ? bytes         data
 
    Compressed data may be either stand-alone or delta-compressed (relative
 to the base picture named in the header).  Delta compression involves
 storing only how the picture differs from the base picture (i.e., only
 portions of the screen that have changed are stored).  This is used to
 to encode animated sequences efficiently.
 
 Compressed data, stand-alone:
 
 For each byte x in the data section:
 
         x = escape byte         Read one more byte, n.  (n is unsigned).
 
                                 If n >= 2, use the next byte n times.
                                 If n = 1, keep reading bytes until a
                                 byte k not equal to 1 is encountered.
                                 Then read the next byte d.
                                 If the number of 1 bytes encountered is o,
                                 use d (256 * o + k) times.  I.e.,
 
                                 if (n == 1) {
                                         o = 0;
                                         while (n == 1) {
                                                o++;
                                                 n = next byte;
                                         }
 
                                         k = n;
                                         d = next byte;
 
                                         Use d (256 * o + k) times.
                                 }
                                 else {
                                         d = next byte;
                                         Use d (n) times.
                                 }
 
         x != escape byte        Use x literally.
 
 Compressed data, delta compressed:
 
 For each byte x in the data section:
 
         x = escape byte         Read one more byte, n.  (n is unsigned).
 
                                 If n >= 3, use the next byte n times.
                                 If n = 1, do the same as for n = 1 in
                                 stand-alone compression (above).
                                 If n = 2, then set n = next byte.
                                         If n = 0, end of picture.
                                         If n >= 2, take n bytes from base
                                         picture.
                                         If n = 1, do the same as for n = 1
                                         in stand-alone compression (above),
                                         but take (256 * o + k) bytes from 
                                         base picture.
 
         x != escape byte        Use x literally.
 
 
 <IFF Format>    *.IFF
  
 4 bytes         "FORM" (FORM chunk ID)
 1 long          length of file that follows
 4 bytes         "ILBM" (InterLeaved BitMap file ID)
 
 4 bytes         "BMHD" (BitMap HeaDer chunk ID)
 1 long          length of chunk [20]
 20 bytes        1 word = image width in pixels
                 1 word = image height in lines
                 1 word = image x-offset [usually 0]
                 1 word = image y-offset [usually 0]
                 1 byte = # bitplanes
                 1 byte = mask (0=no, 1=impl., 2=transparent, 3=lasso)
                 1 byte = compressed [1] or uncompressed [0]
                 1 byte = unused [0]
                 1 word = transparent color (for mask=2)
                 1 byte = x-aspect [5=640x200, 10=320x200/640x400, 20=320x400]
                 1 byte = y-aspect [11]
                 1 word = page width (usually the same as image width)
                 1 word = page height (usually the same as image height)
 
 4 bytes         "CMAP" (ColorMAP chunk ID)
 1 long          length of chunk [3*n where n is the # colors]
 3n bytes        3 bytes per RGB color.  Each color value is a byte
                 and the actual color value is left-justified in the
                 byte such that the most significant bit of the value
                 is the MSB of the byte.  (ie. a color value of 15 ($0F)
                 is stored as $F0)  The bytes are stored in R,G,B order.
 
 4 bytes         "CRNG" (Color RaNGe chunk ID)
 1 long          length of chunk [8]
 8 bytes         1 word = reserved [0]
                 1 word = animation speed (16384 = 60 steps per second)
                 1 word = active [1] or inactive [0]
                 1 byte = left/lower color animation limit
                 1 byte = right/upper color animation limit
 
 4 bytes         "CAMG" (Commodore AMiGa viewport mode chunk ID)
 1 long          length of chunk [4]
 1 long          viewport mode bits (bit 11 = HAM, bit 3 = interlaced)
 
 4 bytes         "BODY" (BODY chunk ID)
 1 long          length of chunk [# bytes of image data that follow]
 ? bytes         actual image data
  
 NOTES: Some of these chunks may not be present in every IFF file, and may
 not be in this order.  You should always look for the ID bytes to find a
 certain chunk.  All chunk IDs are followed by a long value that tells the
 size of the chunk (note that "ILBM" is not a chunk ID).  This is the number of
 bytes that FOLLOW the 4 ID bytes and size longword.  The exception to this is
 the FORM chunk.  The size longword that follows the FORM ID is the size of the
 remainder of the file.  The FORM chunk must always be the first chunk in an
 IFF file.
 
 The R,G,B ranges of AMIGA and ST are different (AMIGA 0...15, ST 0...7),
 as is the maximum number of bitplanes (AMIGA: 5, ST: 4).
 
 Format of body data
  
 An expanded picture is simply a bitmap.  The packing method is PackBits
 (see below), and is identical to MacPaint and DEGAS Elite compressed.
  
 The (decompressed) body data appears in the following order:
  
         line 1 plane 0 ... line 1 plane 1 ... ... line 1 plane m
         [line 1 mask (if appropriate)]
         line 2 plane 0 ... line 2 plane 1 ... ... line 2 plane m
         [line 2 mask (if appropriate)]
         ...
         line x plane 0 ... line x plane 1 ... ... line x plane m
         [line x mask (if appropriate)]
  
 The FORM chunk identifies the type of data:
  
         "ILBM" = interleaved bit map
         "8SVX" = 8-bit sample voice
         "SMUS" = simple music score
         "FTXT" = formatted text (Amiga)
  
 
 <MacPaint>      *.MAC
  
 1 long          version number [0=ignore header, 2=header valid]
 38 * 8 bytes    8x8 brush/fill patterns.  Each byte is a pattern row,
                 and the bytes map the pattern rows top to bottom.  The
                 patterns are stored in the order they appear at the bottom
                 of the MacPaint screen top to bottom, left to right.
 204 bytes       unused
 -------------
 512 bytes       total for header
 
 < 51200 bytes   compressed bitmap data
 -------------
 < 51712 bytes   total
  
 NOTE:  The version number is actually a flag to MacPaint to indicate if
 the brush/fill patterns are present in the file.  If the version is 0,
 the default patterns are used.  Therefore you can simply save a MacPaint
 file by writing a blank header (512 $00 bytes), followed by the packed
 image data.
 
 Bitmap compression:
  
    The bitmap data is for a 576 pixel by 720 pixel monochrome image.
 The packing method is PackBits (see below).  There are 72 bytes per
 scan line.  Each bit represents one pixel; 0 = white, 1 = black.
  
 
 <RGB Intermediate Format>       *.RGB (low resolution only)
 
    This format was invented by Lars Michael to facilitate conversions between
 standard ST picture formats and higher resolution formats like GIF and IFF.
 It supports 12 bits of color resolution by keeping the red, green and blue
 components in separate bit planes.
 
 1 word          resolution (ignored)
 16 word         palette (ignored)
 16000 words     red plane (screen memory)> 1 word          resolution (ignored)
 16 word         palette (ignored)
 16000 words     green plane (screen memory)
 1 word          resolution (ignored)
 16 word         palette (ignored)
 16000 words     blue plane (screen memory)
 ------------
 96102 bytes     total
 
 The format was derived by concatenating three DEGAS .PI1 files together -- 
 one for each color gun.  The RGB value for a pixel is constructed by looking
 at the appropriate pixel in the red plane, green plane, and blue plane.  The
 bitplanes are in standard ST low resolution screen RAM format, but where pixel
 values in screen RAM refer to palette entries (0 through 15), pixel values
 here correspond to absolute R, G, and B values.  The red, green, and blue
 components for each pixel range from 0 to 15 (4 bits), yielding a total of
 12 bits of color information per pixel.  Not coincidentally, this is exactly
 the format of ST palette entries (although on ST's without the extended 
 palette only the lower 3 bits of each color component are used).
 
 You can view a single bit plane on a standard ST by splitting the .RGB file
 into its three DEGAS .PI1 components and setting the palette to successively
 brighter shades of gray.
 
 
 <ComputerEyes Raw Data Format>  *.CE1 (low resolution)
                                 *.CE2 (medium resolution)
                                 
 1 long          [$45594553 or "EYES"]
 1 word          resolution [0 = low res, 1 = medium res]
 8 words         ?
 If resolution = 0 {
 64000 bytes     red plane, 320 x 200, 1 pixel per byte
 64000 bytes     green plane, 320 x 200, 1 pixel per byte
 64000 bytes     blue plane, 320 x 200, 1 pixel per byte
 ------------
 192022 bytes    total
 } 
 else If resolution = 1 {
 128000 words    640 x 200, 1 pixel per word
 ------------
 256022 bytes    total
 }
 
    This is almost two formats in one:
    
         Low resolution:
 
            The planes are arranged vertically, instead of horizontally.
         The first byte is the red component of pixel (0,0), the second is (0,1)
         and the third (0,2).  The 201st corresponds to (1,0), etc.  The 64001st
         byte is the green component of (0,0).
            Only the low six bits of each byte are used.
 
         Medium resolution:
 
            The picture is arranged vertically, instead of horizontally.
         The first word is pixel (0,0), the second is (0,1), and the third
         (0,2).  The 200th is (1,0) etc.
            Each word is divided up into the RGB values for the corresponding
         pixel, as follows:
 
           Bit:  (MSB) 15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00 (LSB)
                       -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
                        0 B4 B3 B2 B1 B0 G4 G3 G2 G1 G0 R4 R3 R2 R1 R0
 
         Bit 15 is not used.
 
 
 <PackBits Compression Algorithm>
 
 The following packing algorithm originated on the Mac, was adopted by
 Electronic Arts/Commodore for use in the IFF standard, and then by Tom
 Hudson for use in DEGAS Elite.  The algorithm is currently used in
 MacPaint, IFF, and DEGAS Elite compressed file formats.  Each scan line
 is packed separately, and packing never extends beyond a scan line.
 
 For a given control byte 'n':
     0 <= n <= 127   : use the next n + 1 bytes literally (no repetition).
  -127 <= n <= -1    : use the next byte -n + 1 times.
          n = -128   : no operation, not used.
 
 -------------------------------------------------------------------------
 
 * Roland Waldi contributed extensive information on the following formats:
 
         GEM, IMG, Doodle, STAD, Imagic Film/Picture, Art Director, IFF
 
 ** John Brochu, ST picture formats guru, provided sage advice and many
    corrections to the following formats:
 
         NeoChrome, DEGAS Elite Compressed, Spectrum 512 Compressed,
         GEM Bit Image, IFF, MacPaint
 
 Version of Wed Jun 26 22:53:08 EDT 1991


