SGI (image file format)

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File Format
Name SGI (image file format)
Ontology
Extension(s) .sgi, .bw, .rgb, .rgba, others
PRONOM x-fmt/140
Wikidata ID Q7514956

SGI image (also known as IRIS, and sometimes called RGB or Irix RGB) is a raster image file format. It is associated with an image library used on Silicon Graphics workstations. The image may be uncompressed, or use RLE compression.

Contents

Format details

File structure

SGI image files start with a 512-byte fixed header, most of which is unused. If the image is uncompressed, the pixel data follows. Compressed images have a scan-line table, followed by the compressed pixel data.

The pixel data is stored bottom-up.

Image types

The following image types are supported:

  • Grayscale, 8 or 16 bits/sample
  • RGB, 8 or 16 bits/sample
  • RGBA, 8 or 16 bits/sample
  • RGB 3-3-2, 8 bits/pixel (obsolete)
  • Colormapped (but no palette is stored in the file) (obsolete)
  • Colormap (file contains only a palette; no image) (obsolete)
  • Grayscale+alpha images also exist, though they're not covered in the specification.

Identification

Files begin with bytes 01 DA.

Specifications

Software

Sample files

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