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Image MIME Reference
JPEG-XR-Sequence

JPEG XR Image Sequence (HEIF Container)

image/jxrs
VS

Portable Pixmap

image/x-portable-pixmap
PPM

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

Equal browser support

Feature Support

Feature JPEG-XR-Sequence PPM
Transparency (Alpha) Yes ✕ No
Animation Support Yes ✕ No
Progressive Loading Yes ✕ No
HDR Support Yes Yes
EXIF Metadata Yes ✕ No
ICC Color Profile Yes ✕ No
JPEG XR Image Sequence (HEIF Container)
image/jxrs
Extension
.jxrs
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 53
Full JPEG-XR-Sequence reference →
Portable Pixmap
image/x-portable-pixmap
Extension
.ppm
Container Netpbm
Compression Uncompressed
Algorithm
None
Color Depth 24-bit (RGB), 48-bit (RGB High Color)
Developed by Jef Poskanzer (Netpbm Project)
Released 1988
Magic Bytes
50 33 (ASCII) or 50 36 (Binary)
Full PPM reference →

Browser Support Comparison

Browser JPEG-XR-Sequence PPM
Chrome Chrome
✕ ✕
Firefox Firefox
✕ ✕
Safari Safari
✕ ✕
Edge Edge
✕ ✕
IE IE (Legacy)
✕ ✕
JPEG-XR-Sequence

JPEG-XR-Sequence Strengths

  • Supports 32-bit floating point HDR color depths natively across an entire animation sequence
  • Combines the advanced coding efficiencies of JPEG XR with the sequence timing and metadata framework of HEIF
  • Shares frame data structures allowing for optimized storage of burst photography
Limitations
  • Extremely rare format with essentially no mainstream software adoption
  • Zero web browser support
  • Overshadowed heavily by HEVC (HEIC sequences) and AV1 (AVIF sequences) which offer superior compression and broader hardware decoding support
PPM

PPM Strengths

  • Absolute structural simplicity allows parsers and renderers (such as custom raytracers) to write directly to the format with virtually no overhead or external libraries
  • Supports 16-bit per channel (48-bit total) precision, preserving deep color accuracy before converting to final delivery formats
  • ASCII encoding ('P3') allows manual editing and visual inspection of RGB values directly within a text editor
Limitations
  • Zero compression results in astronomical file sizes, making it entirely impractical for web delivery or consumer storage
  • Does not natively support an alpha channel for transparency (this is handled by the newer PAM extension format within the Netpbm suite)
  • Lacks support for modern metadata standards like EXIF, XMP, or embedded ICC color profiles

When to choose which format

JPEG-XR-Sequence
Use JPEG-XR-Sequence when…
  • Experimental Animation Workflows
  • HDR Burst Photography Archiving
  • Specialized Medical & Scientific Imaging
PPM
Use PPM when…
  • Intermediary Format for Image Format Conversion
  • Academic Computer Graphics and Raytracing Output
  • Unix/Linux Command-Line Image Pipelines

More comparisons

JPEG-XR-Sequence vs ACES → PPM vs ACES → JPEG-XR-Sequence vs APNG → PPM vs APNG → JPEG-XR-Sequence vs AVCI → PPM vs AVCI → JPEG-XR-Sequence vs AVCS → PPM vs AVCS → JPEG-XR-Sequence vs AVIF → PPM vs AVIF → All comparisons →
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