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Image MIME Reference
JPEG-XS-(HEIF)

JPEG XS Image (HEIF Container)

image/jxsi
VS

Portable Graymap

image/x-portable-graymap
PGM

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

Equal browser support

Feature Support

Feature JPEG-XS-(HEIF) PGM
Transparency (Alpha) Yes ✕ No
Animation Support ✕ No ✕ No
Progressive Loading ✕ No ✕ No
HDR Support Yes Yes
EXIF Metadata Yes ✕ No
ICC Color Profile Yes ✕ No
JPEG XS Image (HEIF Container)
image/jxsi
Extension
.jxsi.jxs.hif
Container HEIF / ISOBMFF (ISO/IEC 23008-12)
Compression Lossy (Visually Lossless) / Mathematically Lossless
Algorithm
JPEG XS (ISO/IEC 21122-1)
Color Depth 8-bit, 10-bit, 12-bit, 14-bit, 16-bit
Developed by Joint Photographic Experts Group (JPEG)
Released 2019
Magic Bytes
XX XX XX XX 66 74 79 70 6A 78 73 69
Full JPEG-XS-(HEIF) reference →
Portable Graymap
image/x-portable-graymap
Extension
.pgm
Container Netpbm
Compression Uncompressed
Algorithm
None
Color Depth 8-bit (Grayscale), 16-bit (Grayscale)
Developed by Jef Poskanzer (Netpbm Project)
Released 1988
Magic Bytes
50 32 (ASCII) or 50 35 (Binary)
Full PGM reference →

Browser Support Comparison

Browser JPEG-XS-(HEIF) PGM
Chrome Chrome
✕ ✕
Firefox Firefox
✕ ✕
Safari Safari
✕ ✕
Edge Edge
✕ ✕
IE IE (Legacy)
✕ ✕
JPEG-XS-(HEIF)

JPEG-XS-(HEIF) Strengths

  • Provides sub-millisecond encoding and decoding latency while retaining visually lossless quality
  • Brings the extensive metadata, EXIF, XMP, and color-profiling capabilities of the HEIF container to JPEG XS
  • Allows grouping of multiple high-quality JPEG XS frames into a single collection file
Limitations
  • Zero web browser compatibility, limiting it entirely to professional and industrial hardware workflows
  • Extremely niche adoption compared to standard HEVC-based HEIC or raw JPEG XS codestreams
  • Requires custom parsing logic to extract the JPEG XS codestream from the HEIF boxes
PGM

PGM Strengths

  • Extremely simple format allows custom parsers to be written from scratch in minimal time
  • Supports 16-bit precision, making it highly valuable for scientific, medical, and height-map data where 8-bit precision is insufficient
  • ASCII encoding ('P2') allows manual editing and visual inspection of pixel values directly within a text editor
Limitations
  • Strictly limited to grayscale; cannot display color
  • Lack of compression results in massive file sizes, making it entirely impractical for web delivery or consumer storage
  • Does not support alpha transparency or modern metadata structures

When to choose which format

JPEG-XS-(HEIF)
Use JPEG-XS-(HEIF) when…
  • Live Broadcast Infrastructure
  • Medical Imaging & Archival
  • Video over IP Networks
  • Automotive & Drone Systems
PGM
Use PGM when…
  • Computer Vision and Machine Learning Pre-processing
  • Scientific and Medical Image Processing
  • Unix/Linux Command-Line Image Pipelines

More comparisons

JPEG-XS-(HEIF) vs ACES → PGM vs ACES → JPEG-XS-(HEIF) vs APNG → PGM vs APNG → JPEG-XS-(HEIF) vs AVCI → PGM vs AVCI → JPEG-XS-(HEIF) vs AVCS → PGM vs AVCS → JPEG-XS-(HEIF) vs AVIF → PGM vs AVIF → All comparisons →
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