CALS Compressed Bitmap

Writable

image

CAL is an image file format used by CALS. CAL files are compressed bitmap formatted files used for storing monochrome images. CAL files were developed in the 1980s to standardize graphics data interchange for electronic publishing for the federal government.

Identify it

Extensions	`.ct1.cal.ras.ct2.ct3.nif.ct4.c4`
Signatures	`737263646f6369643a` at byte 0 (CALS Compressed Bitmap)
PRONOM	`x-fmt/28`
Wikidata	`Q59715886`

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Open it

ImageMagickOpen sourcereads and writes · ImageMagick License
Corel Presentations 11writes
ABViewerreads
Corel Presentations 7reads
PaintShop Photo Pro X3reads
PaintShop Pro X4reads
Q129793reads · shareware

Convert it

To	With	Fidelity	Command and losses
Portable Network Graphics	ImageMagick	Lossless	`convert in.cal out.png` Pixels kept; some metadata, colour profiles or layers may be dropped.
Tagged Image File Format	ImageMagick	Lossless	`convert in.cal out.tif` Pixels kept; some metadata, colour profiles or layers may be dropped.
GIF 89a	ImageMagick	Lossy	`convert in.cal out.gif` Reduced to 256 colours.
JPEG File Interchange Format 1.02	ImageMagick	Lossy	`convert in.cal out.jpg` Lossy compression.
WebP	ImageMagick	Lossy	`convert in.cal out.webp` Lossy compression.

Sources

From Converters (FFmpeg, ImageMagick, Pandoc, LibreOffice), Just Solve the File Format Problem (File Formats Wiki), PRONOM, Wikidata. Updated 2026-10-24.

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