SGI (image file format)

File Format
Name	SGI (image file format)
Ontology	Electronic File Formats Graphics SGI (image file format)
Extension(s)	.sgi, .bw, .rgb, .rgba
PRONOM	x-fmt/140

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, Version 1.00
• The SGI Image File Format, Draft version 0.97

Software

• Netpbm: pnmtosgi, sgitopnm
• ImageMagick (format named "SGI")
• libimage

External links

• Wikipedia article