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Image MIME Reference
MIX

Microsoft Image Extension

image/vnd.mix
VS

Portable Graymap

image/x-portable-graymap
PGM

A complete technical comparison of Microsoft Image Extension and Portable Graymap — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

Equal browser support

Feature Support

Feature MIX PGM
Transparency (Alpha) Yes ✕ No
Animation Support ✕ No ✕ No
Progressive Loading ✕ No ✕ No
HDR Support ✕ No Yes
EXIF Metadata ✕ No ✕ No
ICC Color Profile Yes ✕ No
Microsoft Image Extension
image/vnd.mix
Extension
.mix
Container Microsoft OLE Structured Storage (COM)
Compression Proprietary (Internal JPEG/RLE)
Algorithm
JPEGDeflateProprietary
Color Depth 8-bit, 24-bit, 32-bit (RGBA)
Developed by Microsoft Corporation
Released 1996
Magic Bytes
D0 CF 11 E0 A1 B1 1A E1
Full MIX reference →
Portable Graymap
image/x-portable-graymap
Extension
.pgm
Container Netpbm
Compression Uncompressed
Algorithm
None
Color Depth 8-bit (Grayscale), 16-bit (Grayscale)
Developed by Jef Poskanzer (Netpbm Project)
Released 1988
Magic Bytes
50 32 (ASCII) or 50 35 (Binary)
Full PGM reference →

Browser Support Comparison

Browser MIX PGM
Chrome Chrome
✕ ✕
Firefox Firefox
✕ ✕
Safari Safari
✕ ✕
Edge Edge
✕ ✕
IE IE (Legacy)
✕ ✕
MIX

MIX Strengths

  • Allowed early consumer software to non-destructively edit complex compositions involving photos, text, and vector clipart
  • Shared an architecture with other Microsoft Office products, enabling deep integration (OLE embedding) into Word and PowerPoint at the time
Limitations
  • Completely proprietary and undocumented, leading to a massive loss of historical data for users who archived their family photos in this project format
  • Requires traversing a complex OLE filesystem just to extract the flattened raster image
  • No support in modern image editors like Photoshop, GIMP, or web browsers
PGM

PGM Strengths

  • Extremely simple format allows custom parsers to be written from scratch in minimal time
  • Supports 16-bit precision, making it highly valuable for scientific, medical, and height-map data where 8-bit precision is insufficient
  • ASCII encoding ('P2') allows manual editing and visual inspection of pixel values directly within a text editor
Limitations
  • Strictly limited to grayscale; cannot display color
  • Lack of compression results in massive file sizes, making it entirely impractical for web delivery or consumer storage
  • Does not support alpha transparency or modern metadata structures

When to choose which format

MIX
Use MIX when…
  • Historical Microsoft Picture It! Projects
  • Microsoft PhotoDraw 2000 Graphics
  • Early 2000s Consumer Digital Scrapbooking
PGM
Use PGM when…
  • Computer Vision and Machine Learning Pre-processing
  • Scientific and Medical Image Processing
  • Unix/Linux Command-Line Image Pipelines

More comparisons

MIX vs ACES → PGM vs ACES → MIX vs APNG → PGM vs APNG → MIX vs AVCI → PGM vs AVCI → MIX vs AVCS → PGM vs AVCS → MIX vs AVIF → PGM vs AVIF → All comparisons →
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