ST Picture Formats: Difference between revisions
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(Added MegaPaint format) |
(Added Calamus Raster Graphic) |
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COKE format *.TG1 |
COKE format *.TG1 |
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MegaPaint *.BLD |
MegaPaint *.BLD |
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| + | Calamus Raster Graphic *.CRG |
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PackBits Compression Algorithm |
PackBits Compression Algorithm |
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| ⚫ | |||
| ⚫ | |||
Introductory Information |
Introductory Information |
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------------------------ |
------------------------ |
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1 word image width in pixels [if negative, file is compressed] |
1 word image width in pixels [if negative, file is compressed] |
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1 word image height in pixels |
1 word image height in pixels |
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| − | ------ |
+ | ------- |
4 bytes total for header |
4 bytes total for header |
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| Line 1,744: | Line 1,745: | ||
n = 255 : use the next byte + 1 times and repeat 255 |
n = 255 : use the next byte + 1 times and repeat 255 |
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n>0 and n<255 : output n (literal) |
n>0 and n<255 : output n (literal) |
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| + | |||
| + | |||
| + | <Calamus Raster Graphic> *.CRG |
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| + | |||
| + | 10 bytes file id [CALAMUSCRG] |
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| + | 1 word version? [$03E8] |
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| + | 1 word version? [$0002] |
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| + | 1 long file size, minus 24 |
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| + | 1 word code for the page size? [$0080] |
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| + | 1 long image width in pixels |
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| + | 1 long image height in pixels |
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| + | 1 long unknown [varies] |
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| + | 1 byte unknown [$01] |
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| + | 1 byte unknown [$00] |
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| + | 1 long unknown [$FFFFFFFF] |
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| + | 1 long size of compressed image data in bytes |
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| + | -------- |
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| + | 42 bytes total for header |
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| + | |||
| + | ?? monochrome image adata |
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| + | |||
| + | RLE compression scheme: The compressed data consists of a code byte, followed by one or |
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| + | more data bytes, followed by another code byte, and so on. |
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| + | |||
| + | To decompress: Code byte (N) Instructions |
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| + | N <= 127 Emit the next N+1 bytes literally. |
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| + | N >= 128 Emit the next byte N?127 times. |
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| + | |||
| + | After decompression, pixels are in left-to-right, top-to-bottom order. The format is |
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| + | 8 pixels per byte, most significant bit first, white is 0. Rows are padded to the next |
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| + | byte boundary. |
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