Free webp to jpg
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Image MIME Reference
JNG

JPEG Network Graphics

image/x-jng
VS

JPEG 2000 Compound Image File Format

image/jpm
JPM

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

Equal browser support

Feature Support

Feature JNG JPM
Transparency (Alpha) Yes Yes
Animation Support ✕ No ✕ No
Progressive Loading Yes Yes
HDR Support ✕ No ✕ No
EXIF Metadata Yes Yes
ICC Color Profile Yes Yes
JPEG Network Graphics
image/x-jng
Extension
.jng
Container PNG-style Chunk Structure (JHDR, JDAT, IDAT, IEND)
Compression Lossy (JPEG/DCT for color) / Lossless (Deflate for alpha mask)
Algorithm
JPEG (Discrete Cosine Transform)Deflate (LZ77)
Color Depth 8-bit, 12-bit, 24-bit (RGB), 32-bit (RGBA)
Developed by MNG Development Group (Glenn Randers-Pehrson et al.)
Released 2001
Magic Bytes
8B 4A 4E 47 0D 0A 1A 0A
Full JNG reference →
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 →

Browser Support Comparison

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

JNG Strengths

  • Solved a massive technical hurdle in the early 2000s by combining high-compression lossy photographic data with crisp, 8-bit alpha transparency
  • Utilized the highly robust, extensible chunk-based architecture of the PNG format
  • Provided an excellent, bandwidth-saving alternative to massive 32-bit transparent PNGs for web design
Limitations
  • Failed to achieve critical mass; browser vendors largely abandoned the MNG/JNG standard due to implementation complexity
  • Completely obsolete today, having been superseded by natively supported, superior formats like WebP, AVIF, and HEIC
  • Decoding requires a hybrid engine that can parse PNG chunks while simultaneously decoding a JPEG stream and a Deflate stream, complicating software support
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

When to choose which format

JNG
Use JNG when…
  • Embedded frames in MNG animations
  • Historical web graphics requiring lossy compression with transparency
JPM
Use JPM when…
  • Scanned Document Archiving
  • Mixed Raster Content (MRC) Imaging
  • Digital Libraries

More comparisons

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