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Image MIME Reference
FITS

Flexible Image Transport System

image/fits
VS

Silicon Graphics Image

image/x-rgb
SGI-RGB

A complete technical comparison of Flexible Image Transport System and Silicon Graphics Image — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

Equal browser support

Feature Support

Feature FITS SGI-RGB
Transparency (Alpha) ✕ No Yes
Animation Support ✕ No ✕ No
Progressive Loading ✕ No ✕ No
HDR Support Yes ✕ No
EXIF Metadata ✕ No ✕ No
ICC Color Profile ✕ No ✕ No
Flexible Image Transport System
image/fits
Extension
.fits.fit.fts
Container FITS
Compression Uncompressed / Tile Compressed (Rice, GZIP)
Algorithm
UncompressedRiceGZIPHcompress
Color Depth 8-bit, 16-bit, 32-bit, 64-bit (Float/Double)
Developed by IAU FITS Working Group / NASA
Released 1981
Magic Bytes
53 49 4D 50 4C 45 20 20 3D 20
Full FITS reference →
Silicon Graphics Image
image/x-rgb
Extension
.rgb.sgi.rgba.bw.int.inta
Container SGI Image Header (512 bytes)
Compression Uncompressed / Run-Length Encoding (RLE)
Algorithm
NoneScanline RLE
Color Depth 8-bit (Per Channel), 16-bit (Per Channel)
Developed by Silicon Graphics, Inc. (Paul Haeberli)
Released 1988
Magic Bytes
01 DA
Full SGI-RGB reference →

Browser Support Comparison

Browser FITS SGI-RGB
Chrome Chrome
✕ ✕
Firefox Firefox
✕ ✕
Safari Safari
✕ ✕
Edge Edge
✕ ✕
IE IE (Legacy)
✕ ✕
FITS

FITS Strengths

  • The undisputed global standard for archiving and sharing astronomical data
  • Self-documenting: Headers are written in plain ASCII, ensuring data is readable decades later regardless of software
  • Supports incredibly high dynamic range, N-dimensional arrays, and complex binary tables
Limitations
  • No support in standard consumer software or web browsers
  • Uncompressed raw FITS files from modern telescopes can be excessively large
  • Does not use standard metadata models like EXIF or XMP, requiring specialized parsers
SGI-RGB

SGI-RGB Strengths

  • Supports 16-bit precision per channel and an embedded alpha channel, making it ideal for the demanding compositing workflows of 1990s cinema VFX
  • The scanline-based RLE compression was exceptionally fast to decode on classic MIPS-based SGI workstations
  • Features a straightforward 512-byte header, making it relatively easy to parse and write custom decoders in C or Python
Limitations
  • Completely obsolete and unsupported in modern web environments
  • Replaced entirely by TIFF, OpenEXR, and PNG in modern visual effects and 3D rendering pipelines
  • Lacks support for modern color management via ICC profiles or advanced EXIF metadata

When to choose which format

FITS
Use FITS when…
  • Astronomy & Astrophysics
  • Space Telescope Data (Hubble, JWST)
  • Scientific Data Archiving
  • Spectroscopy
SGI-RGB
Use SGI-RGB when…
  • Legacy 3D Animation and VFX Textures
  • Silicon Graphics IRIX Workstation Archival
  • 1990s Medical Imaging

More comparisons

FITS vs ACES → SGI-RGB vs ACES → FITS vs APNG → SGI-RGB vs APNG → FITS vs AVCI → SGI-RGB vs AVCI → FITS vs AVCS → SGI-RGB vs AVCS → FITS vs AVIF → SGI-RGB vs AVIF → All comparisons →
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