SGI (image file format)

Revision as of 16:19, 2 December 2022

SGI (also known as IRIS, and sometimes called RGB or Irix RGB) is a raster image file format. The image may be uncompressed, or use RLE compression.

SGI probably stands for Silicon Graphics Image.

Image types

SGI supports the following image types:

• 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)

Format

SGI 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 scanline table, followed by the compressed pixel data.

The pixel data is stored from bottom-up, instead of top-down as in most image formats.

Identification

SGI 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

Sample files

• RGB.tar.Z
• https://telparia.com/fileFormatSamples/image/sgi/

External links

• Wikipedia article
• SGI Image File Format File Format Summary, from the Encyclopedia of Graphics File Formats