SGI (image file format)

Latest revision as of 18:24, 4 May 2024

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.

[edit] Format details

[edit] 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.

[edit] 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.

[edit] Identification

Files begin with bytes 01 DA.

[edit] 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

[edit] Software

• Konvertor
• Netpbm: pnmtosgi, sgitopnm
• ImageMagick (format named "SGI")
• Tom's Viewer
• libimage
• Deark

[edit] Sample files

• RGB.tar.Z
• dexvert samples — image/sgi

[edit] Links

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