Image MIME Reference
HEJ2K
JPEG 2000 Image (HEIF Container)
image/hej2k
VS
X Bitmap (Legacy MIME Alias)
image/x-xbm
XBM
A complete technical comparison of JPEG 2000 Image (HEIF Container) and X Bitmap (Legacy MIME Alias) — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.
Equal browser support
Feature Support
| Feature | HEJ2K | XBM |
|---|---|---|
| Transparency (Alpha) | Yes | Yes |
| Animation Support | ✕ No | ✕ No |
| Progressive Loading | Yes | ✕ No |
| HDR Support | Yes | ✕ No |
| EXIF Metadata | Yes | ✕ No |
| ICC Color Profile | Yes | ✕ No |
JPEG 2000 Image (HEIF Container)
image/hej2k
Extension
.hej2
Container
HEIF / ISOBMFF (ISO/IEC 15444-16)
Compression
Lossy / Lossless
Algorithm
JPEG 2000HTJ2K
Color Depth
8-bit, 10-bit, 12-bit, 16-bit
Developed by
ISO/IEC JTC 1 / ITU-T
Released
2019
Magic Bytes
XX XX XX XX 66 74 79 70 6A 32 6B 69
X Bitmap (Legacy MIME Alias)
image/x-xbm
Extension
.xbm
Container
C Source Code Header (.h)
Compression
Uncompressed (Source Code)
Algorithm
None
Color Depth
1-bit (Monochrome)
Developed by
MIT / X Consortium (X Window System)
Released
1988
Magic Bytes
23 64 65 66 69 6e 65 (ASCII '#define')
Browser Support Comparison
| Browser | HEJ2K | XBM |
|---|---|---|
Chrome
|
✕ | ✕ |
Firefox
|
✕ | ✕ |
Safari
|
✕ | ✕ |
Edge
|
✕ | ✕ |
IE (Legacy)
|
✕ |
✓
|
HEJ2K
HEJ2K Strengths
- Brings the extensive capabilities of the HEIF container (like EXIF/XMP, thumbnails, and depth maps) to JPEG 2000
- Supports mathematically lossless compression via wavelet transformation
- High scalability and progressive decoding out of the box
Limitations
- Extremely limited software support outside of niche industries
- Zero native compatibility with web browsers
- High computational complexity compared to simpler formats like JPEG or PNG
XBM
XBM Strengths
- Can be compiled directly into C or C++ source code without needing an external file loader or binary asset manager
- Human-readable structure allows developers to inspect, edit, or hand-craft tiny icons directly within a text editor
- Extremely predictable and lightweight for 1-bit hardware displays and embedded systems
Limitations
- Strictly limited to 1-bit monochrome (black and white) graphics with no gray or color support
- Text-based C syntax creates massive file bloat compared to binary 1-bit formats like PBM
- Completely deprecated in modern web browsers and desktop GUI frameworks
When to choose which format
HEJ2K
Use HEJ2K when…
- Medical Imaging
- Geospatial Data
- Scientific Archiving
XBM
Use XBM when…
- X Window System (X11) Cursors and Icons
- Embedded C/C++ Firmware UI Assets
- Early 1990s Unix Web Graphics