Image MIME Reference
PGM
Portable Graymap
image/x-portable-graymap
VS
QuickTime Image Format
image/x-quicktime
QTIF
A complete technical comparison of Portable Graymap and QuickTime Image Format — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.
Equal browser support
Feature Support
| Feature | PGM | QTIF |
|---|---|---|
| Transparency (Alpha) | ✕ No | Yes |
| Animation Support | ✕ No | ✕ No |
| Progressive Loading | ✕ No | ✕ No |
| HDR Support | Yes | ✕ No |
| EXIF Metadata | ✕ No | ✕ No |
| ICC Color Profile | ✕ No | ✕ No |
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)
QuickTime Image Format
image/x-quicktime
Extension
.qtif.qti.qif
Container
QuickTime Atom Container
Compression
Varies (JPEG, SMC, Apple Video, Cinepak, Uncompressed)
Algorithm
QuickTime Image Compression Manager (ICM) Codecs
Color Depth
1-bit to 32-bit (Varies depending on the enclosed codec)
Developed by
Apple Computer, Inc.
Released
1991
Magic Bytes
Varies (Typically begins with a 32-bit size integer followed by 69 64 73 63 ('idsc'))
Browser Support Comparison
| Browser | PGM | QTIF |
|---|---|---|
Chrome
|
✕ | ✕ |
Firefox
|
✕ | ✕ |
Safari
|
✕ | ✕ |
Edge
|
✕ | ✕ |
IE (Legacy)
|
✕ | ✕ |
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
QTIF
QTIF Strengths
- Extremely flexible architecture allowing it to encapsulate virtually any image compression algorithm available on the host machine
- Supported 32-bit images with alpha channels (transparency) long before PNG became an established standard
Limitations
- Fundamentally tied to Apple's deprecated QuickTime architecture, rendering the files almost entirely unreadable on modern systems without specialized legacy software or FFmpeg
- The 'wrapper' nature of the format means that even if a parser can read the QTIF container, it may fail to render the image if it lacks the specific proprietary codec (like Apple SMC) used to compress the pixel data
- Zero native support in modern web browsers
When to choose which format
PGM
Use PGM when…
- Computer Vision and Machine Learning Pre-processing
- Scientific and Medical Image Processing
- Unix/Linux Command-Line Image Pipelines
QTIF
Use QTIF when…
- Classic Mac OS Applications and Backgrounds
- QuickTime VR Panorama Textures
- 1990s CD-ROM Multimedia Assets