Image MIME Reference
Generic-RAW
Digital Camera Raw (Generic Linux MIME)
image/x-dcraw
VS
JPEG 2000 Core Image File
image/jp2
JPEG-2000
A complete technical comparison of Digital Camera Raw (Generic Linux MIME) and JPEG 2000 Core Image File — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.
JPEG-2000 wins on browser support
Feature Support
| Feature | Generic-RAW | JPEG-2000 |
|---|---|---|
| Transparency (Alpha) | ✕ No | Yes |
| Animation Support | ✕ No | ✕ No |
| Progressive Loading | ✕ No | Yes |
| HDR Support | Yes | Yes |
| EXIF Metadata | Yes | Yes |
| ICC Color Profile | Yes | Yes |
Digital Camera Raw (Generic Linux MIME)
image/x-dcraw
Extension
.raw
Container
Varies (Predominantly TIFF/EP)
Compression
Lossless / Uncompressed
Algorithm
Varies (Often Lossless JPEG ITU-T81 or uncompressed)
Color Depth
12-bit, 14-bit, 16-bit
Developed by
freedesktop.org (MIME mapping) / Dave Coffin (dcraw tool)
Released
1997
Magic Bytes
Varies by vendor format
JPEG 2000 Core Image File
image/jp2
Extension
.jp2.j2k.jpf.jpx.jpm
Container
JP2 (ISO/IEC 15444-1)
Compression
Lossy / Lossless
Algorithm
Discrete Wavelet Transform (DWT)
Color Depth
8-bit, 16-bit, 32-bit, 38-bit
Developed by
Joint Photographic Experts Group
Released
2000
Magic Bytes
00 00 00 0C 6A 50 20 20 0D 0A 87 0A
Browser Support Comparison
| Browser | Generic-RAW | JPEG-2000 |
|---|---|---|
Chrome
|
✕ | ✕ |
Firefox
|
✕ | ✕ |
Safari
|
✕ |
✓ 5+
|
Edge
|
✕ | ✕ |
IE (Legacy)
|
✕ | ✕ |
Generic-RAW
Generic-RAW Strengths
- Provides a unified, highly useful catch-all MIME type for application developers who just need to know if a file is a raw image, rather than tracking 50+ individual camera extensions
- Deeply integrated into the Linux desktop ecosystem, ensuring file manager thumbnails work seamlessly via tools like ufraw-thumbnailer
Limitations
- Not an official IANA standard
- Can cause conflicts where standard TIFF files are misidentified as raw camera data by over-aggressive MIME sniffers
- The underlying 'dcraw' tool was abandoned by its creator in 2018 (though its successor, LibRaw, continues to maintain the ecosystem)
JPEG-2000
JPEG-2000 Strengths
- Superior compression efficiency over baseline JPEG without introducing blocking artifacts
- True mathematically lossless compression available in the same format
- Extremely scalable: a single file can be decoded at various resolutions (thumbnails to full size) without loading the entire file
Limitations
- Very poor native web browser support prevents it from being a web standard
- High computational complexity makes encoding and decoding significantly slower than JPEG
- Early patent concerns and complex licensing hindered its initial adoption rate
When to choose which format
Generic-RAW
Use Generic-RAW when…
- Linux Desktop File Associations (GNOME/KDE)
- Thumbnail Generation for Raw Images (UFRaw/LibRaw)
- Server-side Image Processing Fallbacks
JPEG-2000
Use JPEG-2000 when…
- Digital Cinema (DCP)
- Medical Imaging (DICOM)
- Geospatial Data
- Archival Preservation