Calamus Raster Graphic
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== Identification == | == Identification == | ||
CRG files apparently begin with the ASCII signature "{{magic|CALAMUSCRG}}". | CRG files apparently begin with the ASCII signature "{{magic|CALAMUSCRG}}". | ||
| + | |||
| + | == Format details == | ||
| + | ''[Partial decoding, based on analysis of a small number of CRG files. This may be incorrect.]'' | ||
| + | |||
| + | Multi-byte integers are big-endian. | ||
| + | |||
| + | {| class="wikitable" | ||
| + | ! Offset !! Length !! Field !! Observed values !! Details | ||
| + | |- | ||
| + | |0 || 10 || signature || "<code>CALAMUSCRG</code>" || | ||
| + | |- | ||
| + | |10 || 2 || || <code>03 e8</code> || Unknown. By analogy to [[Calamus Vector Graphic|CVG]], maybe a code for the format version. | ||
| + | |- | ||
| + | |12 || 2 || || <code>00 02</code> || Unknown. By analogy to CVG, maybe a code for the page size. | ||
| + | |- | ||
| + | |14 || 4 || || (file size, minus 24) || | ||
| + | |- | ||
| + | |18 || 2 || || <code>00 80</code> || Unknown | ||
| + | |- | ||
| + | |20 || 4 || width || || Image width in pixels | ||
| + | |- | ||
| + | |24 || 4 || height || || Image height in pixels | ||
| + | |- | ||
| + | |28 || 4 || || (various) || Unknown | ||
| + | |- | ||
| + | |32 || 1 || || <code>01</code> || Unknown | ||
| + | |- | ||
| + | |33 || 1 || || <code>00</code> || Unknown | ||
| + | |- | ||
| + | |34 || 4 || || <code>ff ff ff ff</code> || Unknown | ||
| + | |- | ||
| + | |38 || 4 || cmpr_size || || Size of compressed image data, in bytes | ||
| + | |- | ||
| + | |42 || cmpr_size || cmpr_image_data || || Compressed image data (see below) | ||
| + | |} | ||
| + | |||
| + | === RLE compression === | ||
| + | The compressed data consists of a code byte, followed by one or more data bytes, followed by another code byte, and so on. To decompress: | ||
| + | {| class="wikitable" | ||
| + | ! Code byte (N) !! Instructions | ||
| + | |- | ||
| + | |N ≤ 127 || Emit the next N 1 bytes literally. | ||
| + | |- | ||
| + | |N ≥ 128 || Emit the next byte N−127 times. | ||
| + | |} | ||
| + | |||
| + | (This is essentially the same algorithm as in [[TGA]], but byte-oriented instead of pixel-oriented.) | ||
| + | |||
| + | After decompression, pixels are in left-to-right, top-to-bottom order. The format is 8 pixels per byte, most significant bit first, white is 0. Rows are padded to the next byte boundary. | ||
== Software == | == Software == | ||
| Line 15: | Line 64: | ||
* [[XnView]] (Does not seem to work perfectly.) | * [[XnView]] (Does not seem to work perfectly.) | ||
* {{Deark}} supports some CRG files | * {{Deark}} supports some CRG files | ||
| + | * [[RECOIL]] | ||
== Sample files == | == Sample files == | ||
* http://cd.textfiles.com/suzybatari2/new_file/extras/dtp/calamus/cal_pics/ | * http://cd.textfiles.com/suzybatari2/new_file/extras/dtp/calamus/cal_pics/ | ||
| + | * {{DexvertSamples|image/crg}} | ||
Latest revision as of 02:57, 28 December 2023
Calamus Raster Graphic (CRG) is a graphics format associated with the Calamus desktop publishing software by invers Software. At least some CRG images are compressed using a simple run-length encoding scheme.
Refer to Calamus for more information about the software, and related formats.
Contents |
[edit] Identification
CRG files apparently begin with the ASCII signature "CALAMUSCRG".
[edit] Format details
[Partial decoding, based on analysis of a small number of CRG files. This may be incorrect.]
Multi-byte integers are big-endian.
| Offset | Length | Field | Observed values | Details |
|---|---|---|---|---|
| 0 | 10 | signature | "CALAMUSCRG" |
|
| 10 | 2 | 03 e8 |
Unknown. By analogy to CVG, maybe a code for the format version. | |
| 12 | 2 | 00 02 |
Unknown. By analogy to CVG, maybe a code for the page size. | |
| 14 | 4 | (file size, minus 24) | ||
| 18 | 2 | 00 80 |
Unknown | |
| 20 | 4 | width | Image width in pixels | |
| 24 | 4 | height | Image height in pixels | |
| 28 | 4 | (various) | Unknown | |
| 32 | 1 | 01 |
Unknown | |
| 33 | 1 | 00 |
Unknown | |
| 34 | 4 | ff ff ff ff |
Unknown | |
| 38 | 4 | cmpr_size | Size of compressed image data, in bytes | |
| 42 | cmpr_size | cmpr_image_data | Compressed image data (see below) |
[edit] RLE compression
The compressed data consists of a code byte, followed by one or more data bytes, followed by another code byte, and so on. To decompress:
| Code byte (N) | Instructions |
|---|---|
| N ≤ 127 | Emit the next N 1 bytes literally. |
| N ≥ 128 | Emit the next byte N−127 times. |
(This is essentially the same algorithm as in TGA, but byte-oriented instead of pixel-oriented.)
After decompression, pixels are in left-to-right, top-to-bottom order. The format is 8 pixels per byte, most significant bit first, white is 0. Rows are padded to the next byte boundary.
