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Image MIME Reference
JPEG-XR-(HEIF)

JPEG XR Image (HEIF Container)

image/jxra
VS

Silicon Graphics Image

image/x-rgb
SGI-RGB

A complete technical comparison of JPEG XR Image (HEIF Container) and Silicon Graphics Image — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

Equal browser support

Feature Support

Feature JPEG-XR-(HEIF) SGI-RGB
Transparency (Alpha) Yes Yes
Animation Support ✕ No ✕ No
Progressive Loading Yes ✕ No
HDR Support Yes ✕ No
EXIF Metadata Yes ✕ No
ICC Color Profile Yes ✕ No
JPEG XR Image (HEIF Container)
image/jxra
Extension
.jxra
Container HEIF / ISOBMFF (ISO/IEC 23008-12 / Annex F of ITU-T T.832)
Compression Lossy / Lossless
Algorithm
JPEG XR (Lapped Biorthogonal Transform)
Color Depth 8-bit, 16-bit, 32-bit (Float)
Developed by ISO/IEC JTC 1 / ITU-T
Released 2019
Magic Bytes
XX XX XX XX 66 74 79 70 6A 78 72 41
Full JPEG-XR-(HEIF) 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 JPEG-XR-(HEIF) SGI-RGB
Chrome Chrome
✕ ✕
Firefox Firefox
✕ ✕
Safari Safari
✕ ✕
Edge Edge
✕ ✕
IE IE (Legacy)
✕ ✕
JPEG-XR-(HEIF)

JPEG-XR-(HEIF) Strengths

  • Combines the deep color (32-bit float) and mathematically lossless compression of JPEG XR with the robust metadata architecture of HEIF
  • Allows grouping multiple images, exposure brackets, or focal stacks into a single file collection
Limitations
  • Practically non-existent software and operating system support compared to standard HEIC or legacy JPEG XR (.jxr)
  • Zero web browser support, rendering it entirely unsuitable for public web deployment
  • Eclipsed by modern standards like AVIF and JPEG XL which offer superior compression with much broader industry backing
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

JPEG-XR-(HEIF)
Use JPEG-XR-(HEIF) when…
  • Specialized Archival
  • Experimental Imaging Workflows
  • High Dynamic Range (HDR) Imaging
SGI-RGB
Use SGI-RGB when…
  • Legacy 3D Animation and VFX Textures
  • Silicon Graphics IRIX Workstation Archival
  • 1990s Medical Imaging

More comparisons

JPEG-XR-(HEIF) vs ACES → SGI-RGB vs ACES → JPEG-XR-(HEIF) vs APNG → SGI-RGB vs APNG → JPEG-XR-(HEIF) vs AVCI → SGI-RGB vs AVCI → JPEG-XR-(HEIF) vs AVCS → SGI-RGB vs AVCS → JPEG-XR-(HEIF) vs AVIF → SGI-RGB vs AVIF → All comparisons →
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