Image MIME Reference
HTJ2K-(JPH)
High-Throughput JPEG 2000 Image
image/jph
VS
RealNetworks RealPix
image/vnd.rn-realpix
RealPix
A complete technical comparison of High-Throughput JPEG 2000 Image and RealNetworks RealPix — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.
Equal browser support
Feature Support
| Feature | HTJ2K-(JPH) | RealPix |
|---|---|---|
| Transparency (Alpha) | Yes | Yes |
| Animation Support | ✕ No | Yes |
| Progressive Loading | Yes | Yes |
| HDR Support | Yes | ✕ No |
| EXIF Metadata | Yes | ✕ No |
| ICC Color Profile | Yes | ✕ No |
High-Throughput JPEG 2000 Image
image/jph
Extension
.jph
Container
JPH (ISO/IEC 15444-15)
Compression
Lossy / Lossless
Algorithm
High-Throughput JPEG 2000 (HTJ2K)
Color Depth
8-bit, 16-bit, 32-bit, 38-bit
Developed by
Joint Photographic Experts Group (JPEG)
Released
2019
Magic Bytes
00 00 00 0C 6A 50 20 20 0D 0A 87 0A ... 66 74 79 70 6A 70 68 20
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
Browser Support Comparison
| Browser | HTJ2K-(JPH) | RealPix |
|---|---|---|
Chrome
|
✕ | ✕ |
Firefox
|
✕ | ✕ |
Safari
|
✕ | ✕ |
Edge
|
✕ | ✕ |
IE (Legacy)
|
✕ | ✕ |
HTJ2K-(JPH)
HTJ2K-(JPH) Strengths
- Delivers orders of magnitude faster encoding and decoding than standard JPEG 2000 by utilizing a new, parallelizable block coder
- Supports mathematically lossless and lossy compression within the same codestream architecture
- Allows for resolution scalability, progressive decoding, and region-of-interest extraction without needing to decode the entire image
Limitations
- Zero native web browser support, requiring specialized libraries, API conversions, or WebAssembly (like OpenJPH.js) for web deployment
- Lack of broad consumer awareness, keeping it confined to professional, medical, and scientific workflows
- Requires more advanced software ecosystems to decode than ubiquitous formats like JPEG or WebP
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
HTJ2K-(JPH)
Use HTJ2K-(JPH) when…
- Medical Imaging (DICOM)
- Geospatial Data
- Digital Cinema
- Professional Archiving
RealPix
Use RealPix when…
- Historical Dial-up Streaming Presentations
- RealPlayer Slideshows
- Bandwidth-efficient 'Video' Alternatives (late 1990s)