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John Brochu, author of the famed "PicSwitch", sent me a letter and a disk containing modified picture format descriptions for NeoChrome, DEGAS Elite Compressed, Spectrum 512 Compressed, GEM Bit Image, IFF, and MacPaint formats. John also sent a description of the PackBits compression method used in DEGAS Elite, IFF, and MacPaint formats. Here's the new version with his corrections. Many thanks go to John for his contributions, and also to Gerfried Klein who sent the MacPaint description as described by by *pple, corp. Dave Baggett dmb@wam.umd.edu | dmb@TIS.COM PS> The "GEM Bit Image" description in previous versions describes an outdated version of this format which has been replaced by what is described below. John believes that the old format was never actually implemented, so I took the description out. ----------------------------------- >8 ---------------------------------------- ST Picture Formats ------------------ Edited by: David Baggett 5640 Vantage Point Road Columbia, MD 21044 USA (301) 596-4779 (usenet: dmb@TIS.COM) (Please report errors or additions) Copyright (C) 1988, 1989, 1990 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 Phil Blanchfield Jason Blochowiak John Brochu** David Brooks Neil Forsyth Stefan Hoehn Gerfried Klein Ken MacLeod Jim McCabe Darek Mihocka David Mumper 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 Art Director *.ART C.O.L.R. Object Editor Mural *.MUR Doodle *.DOO Animatic Film *.FLM GEM Bit Image *.IMG STAD *.PAC Imagic Film/Picture *.IC? ? = 1, 2, 3 IFF *.IFF 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 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 <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). <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 <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) 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 <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, 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. 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. <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 May 16 18:02:25 EDT 1990