SGI (image file format)
From Just Solve the File Format Problem
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.
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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
- The SGI Image File Format, Draft version 0.97: ftp.sgi.com archive → sgi/graphics/SGIIMAGESPEC
- The SGI Image File Format, Version 1.00
- Another copy: ftp.sgi.com_June2018 → ftp.sgi.com/sgi/graphics/grafica/sgiimage.html
- SGI RGB Image Format
Software
- Konvertor
- Netpbm: pnmtosgi, sgitopnm
- ImageMagick (format named "SGI")
- Tom's Viewer
- libimage
- Deark
