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Image MIME Reference
JPM

JPEG 2000 Compound Image File Format

image/jpm
VS

RealNetworks RealPix

image/vnd.rn-realpix
RealPix

A complete technical comparison of JPEG 2000 Compound Image File Format and RealNetworks RealPix — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

Equal browser support

Feature Support

Feature JPM RealPix
Transparency (Alpha) Yes Yes
Animation Support ✕ No Yes
Progressive Loading Yes Yes
HDR Support ✕ No ✕ No
EXIF Metadata Yes ✕ No
ICC Color Profile Yes ✕ No
JPEG 2000 Compound Image File Format
image/jpm
Extension
.jpm.jpgm
Container ISOBMFF / JPM (ISO/IEC 15444-6)
Compression Lossy / Lossless / Mixed Raster Content (MRC)
Algorithm
JPEG 2000JBIG2JPEGMMR
Color Depth 1-bit (Text/Masks), 8-bit, 16-bit, 24-bit
Developed by Joint Photographic Experts Group (JPEG)
Released 2003
Magic Bytes
00 00 00 0C 6A 50 20 20 0D 0A 87 0A ... 66 74 79 70 6A 70 6D 20
Full JPM reference →
RealNetworks RealPix
image/vnd.rn-realpix
Extension
.rp
Container IMFL (XML Markup)
Compression Uncompressed (Plain Text Markup)
Algorithm
None (Plain Text)
Color Depth Dependent on referenced images
Developed by RealNetworks
Released 1998
Magic Bytes
3C 69 6D 66 6C
Full RealPix reference →

Browser Support Comparison

Browser JPM RealPix
Chrome Chrome
✕ ✕
Firefox Firefox
✕ ✕
Safari Safari
✕ ✕
Edge Edge
✕ ✕
IE IE (Legacy)
✕ ✕
JPM

JPM Strengths

  • Highly optimized for scanned documents, drastically reducing file sizes without sacrificing the readability of text or the quality of embedded photos
  • Supports multi-page documents within a single file
  • Object-based architecture allows for complex layout representation and independent extraction of elements
Limitations
  • Failed to achieve widespread adoption, largely being overshadowed by PDF/A and DjVu
  • Zero native web browser compatibility
  • Requires complex, specialized software to properly encode and decode the multi-layered MRC structure
RealPix

RealPix Strengths

  • Allowed for 'Ken Burns'-style animated slideshows at a fraction of the bandwidth required for actual video, crucial for 1990s dial-up connections
  • Plain text XML architecture made it easy for developers and hobbyists to hand-code complex multimedia presentations
  • Perfectly synchronized with RealAudio streams using SMIL-like timing parameters
Limitations
  • Completely obsolete and heavily reliant on the proprietary, defunct RealPlayer browser plugin
  • Not a true image format, causing confusion when handled by standard image processing libraries which expect binary pixel data
  • Lacks modern CSS or HTML5 canvas equivalents without completely rewriting the presentation logic

When to choose which format

JPM
Use JPM when…
  • Scanned Document Archiving
  • Mixed Raster Content (MRC) Imaging
  • Digital Libraries
RealPix
Use RealPix when…
  • Historical Dial-up Streaming Presentations
  • RealPlayer Slideshows
  • Bandwidth-efficient 'Video' Alternatives (late 1990s)

More comparisons

JPM vs ACES → RealPix vs ACES → JPM vs APNG → RealPix vs APNG → JPM vs AVCI → RealPix vs AVCI → JPM vs AVCS → RealPix vs AVCS → JPM vs AVIF → RealPix vs AVIF → All comparisons →
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