Image MIME Reference
Alias-PIX
Alias PIX Image
image/x-alias-pix
VS
Compressed GIMP XCF Image
image/x-compressed-xcf
Compressed-XCF
A complete technical comparison of Alias PIX Image and Compressed GIMP XCF Image — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.
Equal browser support
Feature Support
| Feature | Alias-PIX | Compressed-XCF |
|---|---|---|
| Transparency (Alpha) | ✕ No | Yes |
| Animation Support | ✕ No | Yes |
| Progressive Loading | ✕ No | ✕ No |
| HDR Support | ✕ No | Yes |
| EXIF Metadata | ✕ No | Yes |
| ICC Color Profile | ✕ No | Yes |
Alias PIX Image
image/x-alias-pix
Extension
.pix.als.alias.img
Container
Alias PIX Header
Compression
Run-Length Encoding (RLE)
Algorithm
RLE
Color Depth
24-bit (RGB), 8-bit (Matte/Grayscale variant)
Developed by
Alias Research (Later Alias|Wavefront / Autodesk)
Released
Early 1990s
Magic Bytes
No explicit magic bytes (Relies on 10-byte integer header)
Compressed GIMP XCF Image
image/x-compressed-xcf
Extension
.xcf.gz.xcf.bz2.xcfgz.xcfbz2
Container
Gzip or Bzip2 Archive
Compression
Gzip (Deflate) / Bzip2
Algorithm
DeflateBWT (Burrows-Wheeler)
Color Depth
8-bit (Per Channel), 16-bit (Integer/Floating Point), 32-bit (Integer/Floating Point)
Developed by
The GIMP Team
Released
1995
Magic Bytes
1F 8B 08 (gzip) or 42 5A 68 (bzip2)
Browser Support Comparison
| Browser | Alias-PIX | Compressed-XCF |
|---|---|---|
Chrome
|
✕ | ✕ |
Firefox
|
✕ | ✕ |
Safari
|
✕ | ✕ |
Edge
|
✕ | ✕ |
IE (Legacy)
|
✕ | ✕ |
Alias-PIX
Alias-PIX Strengths
- The highly simplified structure made it incredibly fast to encode and decode on early 1990s SGI hardware
- Lossless Run-Length Encoding (RLE) saved disk space without degrading the quality of final 3D renders
Limitations
- Completely obsolete, having been replaced by more robust formats like TIFF, TGA, and EXR in modern 3D pipelines
- The lack of a distinct magic byte signature makes reliable automated file detection almost impossible
- Does not support integrated alpha channels, instead requiring cumbersome, separate 'Matte' files to denote transparency
Compressed-XCF
Compressed-XCF Strengths
- Drastically reduces the massive file sizes of standard XCF project files, saving significant disk space
- Preserves 100% of the non-destructive editing data (layers, masks, paths, guides) from the GIMP workspace
- Uses standard, universally supported compression algorithms (gzip/bzip2) meaning the archive can be rescued or extracted by standard OS tools if GIMP is unavailable
Limitations
- Increases file load and save times due to the CPU overhead required to compress and decompress the massive pixel arrays
- Impossible for automated tools to parse metadata or dimensions without first unarchiving the payload into memory
- File extension combinations (.xcf.gz) can confuse basic MIME sniffers which stop reading at the .gz extension
When to choose which format
Alias-PIX
Use Alias-PIX when…
- Legacy Alias PowerAnimator Textures
- 1990s SGI Workstation Render Outputs
- Historical 3D Graphics Archival
Compressed-XCF
Use Compressed-XCF when…
- GIMP Multi-layer Project Archival
- Saving disk space for complex raster edits
- Open-source graphic design workflows