Calamus Raster Graphic

File Format
Name	Calamus Raster Graphic
Ontology	Electronic File Formats Graphics Calamus Raster Graphic
Extension(s)	.crg

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.

Identification

CRG files apparently begin with the ASCII signature "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.

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)

RLE compression

Code byte (N)	Instructions
N ≤ 127	Emit the next N+1 bytes literally.
N ≥ 128	Emit the next byte N−127 times.

After decompression, pixels are in left-to-right, top-to-bottom order. 8 pixels per byte, most significant bit first, white is 0. Rows are padded to the next byte boundary.

Software

• Konvertor
• XnView (Does not seem to work perfectly.)
• Deark supports some CRG files

Sample files

• http://cd.textfiles.com/suzybatari2/new_file/extras/dtp/calamus/cal_pics/