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Image MIME Reference
CMU-Raster

CMU Window Manager Raster

image/x-cmu-raster
VS

FlashPix

image/vnd.fpx
FPX

A complete technical comparison of CMU Window Manager Raster and FlashPix — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

Equal browser support

Feature Support

Feature CMU-Raster FPX
Transparency (Alpha) ✕ No Yes
Animation Support ✕ No ✕ No
Progressive Loading ✕ No ✕ No
HDR Support ✕ No ✕ No
EXIF Metadata ✕ No Yes
ICC Color Profile ✕ No Yes
CMU Window Manager Raster
image/x-cmu-raster
Extension
.ras
Container CMU Window Manager Bitmap
Compression Uncompressed
Algorithm
None
Color Depth 1-bit (Monochrome), 8-bit (Indexed/Grayscale)
Developed by Carnegie Mellon University (CMU)
Released 1980s
Magic Bytes
F1 00 40 BB
Full CMU-Raster reference →
FlashPix
image/vnd.fpx
Extension
.fpx
Container Microsoft OLE Structured Storage (COM)
Compression JPEG (Lossy) / Uncompressed / Single-color (Solid)
Algorithm
JPEGNone
Color Depth 8-bit (Grayscale/Indexed), 24-bit (RGB), 32-bit (CMYK/RGBA)
Developed by Eastman Kodak, Microsoft, Hewlett-Packard, Live Picture
Released 1996
Magic Bytes
D0 CF 11 E0 A1 B1 1A E1
Full FPX reference →

Browser Support Comparison

Browser CMU-Raster FPX
Chrome Chrome
✕ ✕
Firefox Firefox
✕ ✕
Safari Safari
✕ ✕
Edge Edge
✕ ✕
IE IE (Legacy)
✕ ✕
CMU-Raster

CMU-Raster Strengths

  • Incredibly simple, uncompressed binary structure that was easy for early, memory-constrained UNIX workstations to parse and render
Limitations
  • Completely obsolete and unsupported outside of niche historical command-line tools like Netpbm
  • The shared '.ras' file extension causes frequent file misidentification and system conflicts
  • Lacks all modern imaging features, including metadata, compression, and alpha channel transparency
FPX

FPX Strengths

  • Allowed early, low-RAM computers to view and edit massive, high-resolution digital photos instantly by only loading the needed tiles and resolutions
  • Pioneered the multi-resolution pyramid and tiling concepts heavily used today in modern deep-zoom and web mapping applications (like Google Maps)
Limitations
  • Completely obsolete and unsupported by modern web browsers or operating systems
  • Uses the complex, proprietary Microsoft OLE container format, making it incredibly difficult to parse or extract data from without dedicated legacy libraries
  • Prone to being misidentified by MIME sniffers as an old Microsoft Office document

When to choose which format

CMU-Raster
Use CMU-Raster when…
  • Historical UNIX / Andrew Project Archival
  • Legacy Academic Computing Research
FPX
Use FPX when…
  • Legacy Digital Photography
  • Kodak Picture CDs (Historical)
  • Early High-Resolution Image Viewers

More comparisons

CMU-Raster vs ACES → FPX vs ACES → CMU-Raster vs APNG → FPX vs APNG → CMU-Raster vs AVCI → FPX vs AVCI → CMU-Raster vs AVCS → FPX vs AVCS → CMU-Raster vs AVIF → FPX vs AVIF → All comparisons →
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