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Image MIME Reference
JPM

JPEG 2000 Compound Image File Format

image/jpm
VS

PiCture eXchange

image/x-pcx
PCX

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

Equal browser support

Feature Support

Feature JPM PCX
Transparency (Alpha) Yes ✕ No
Animation Support ✕ No ✕ No
Progressive Loading Yes ✕ No
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 →
PiCture eXchange
image/x-pcx
Extension
.pcx
Container ZSoft Proprietary Header (128 bytes)
Compression Run-Length Encoding (RLE)
Algorithm
ZSoft RLE
Color Depth 1-bit (Monochrome), 4-bit (16 colors), 8-bit (256 colors), 24-bit (True Color)
Developed by ZSoft Corporation
Released 1985
Magic Bytes
0A (followed by version, e.g., 0A 05 01 08)
Full PCX reference →

Browser Support Comparison

Browser JPM PCX
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
PCX

PCX Strengths

  • Incredibly simple RLE algorithm makes it very fast to decode, which was historically vital for early 3D video game engines
  • Retains crisp, lossless pixel data suitable for pixel art and interface assets
  • Well-documented and highly supported by older desktop publishing and image editing software
Limitations
  • Extremely inefficient compression by modern standards, producing large file sizes compared to PNG
  • Lacks modern imaging features such as alpha channel transparency, EXIF metadata, and color profiles
  • Zero support in web browsers; must be converted to PNG for web use

When to choose which format

JPM
Use JPM when…
  • Scanned Document Archiving
  • Mixed Raster Content (MRC) Imaging
  • Digital Libraries
PCX
Use PCX when…
  • MS-DOS and Early Windows Graphics
  • 1990s Video Game Assets (Textures, UI)
  • Retro Computing Archival

More comparisons

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