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Image MIME Reference
Compressed-XCF

Compressed GIMP XCF Image

image/x-compressed-xcf
VS

Portable Bitmap

image/x-portable-bitmap
PBM

A complete technical comparison of Compressed GIMP XCF Image and Portable Bitmap — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

Equal browser support

Feature Support

Feature Compressed-XCF PBM
Transparency (Alpha) Yes ✕ No
Animation Support Yes ✕ No
Progressive Loading ✕ No ✕ No
HDR Support Yes ✕ No
EXIF Metadata Yes ✕ No
ICC Color Profile Yes ✕ No
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)
Full Compressed-XCF reference →
Portable Bitmap
image/x-portable-bitmap
Extension
.pbm
Container Netpbm
Compression Uncompressed
Algorithm
None
Color Depth 1-bit (Monochrome)
Developed by Jef Poskanzer (Netpbm Project)
Released 1988
Magic Bytes
50 31 (ASCII) or 50 34 (Binary)
Full PBM reference →

Browser Support Comparison

Browser Compressed-XCF PBM
Chrome Chrome
✕ ✕
Firefox Firefox
✕ ✕
Safari Safari
✕ ✕
Edge Edge
✕ ✕
IE IE (Legacy)
✕ ✕
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
PBM

PBM Strengths

  • Absolute structural simplicity allows parsers to be written from scratch with just a few lines of code
  • ASCII encoding allows manual editing and debugging directly within a standard text editor
  • Serves as a flawless, lossless intermediary for 1-bit raster data like scanned documents or barcodes
Limitations
  • Strictly limited to 1-bit monochrome images; cannot natively display shades of gray or color
  • Lack of compression results in extremely large file sizes, particularly when using the ASCII 'P1' encoding
  • No support for alpha transparency or modern metadata standards like EXIF

When to choose which format

Compressed-XCF
Use Compressed-XCF when…
  • GIMP Multi-layer Project Archival
  • Saving disk space for complex raster edits
  • Open-source graphic design workflows
PBM
Use PBM when…
  • Optical Character Recognition (OCR) Pre-processing
  • Unix/Linux Command-Line Image Pipelines
  • Academic Image Processing Teaching

More comparisons

Compressed-XCF vs ACES → PBM vs ACES → Compressed-XCF vs APNG → PBM vs APNG → Compressed-XCF vs AVCI → PBM vs AVCI → Compressed-XCF vs AVCS → PBM vs AVCS → Compressed-XCF vs AVIF → PBM vs AVIF → All comparisons →
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