Image MIME Reference
XBM
X Bitmap (Legacy MIME Alias)
image/x-xbm
VS
Pixologic ZBrush PCX
image/vnd.zbrush.pcx
ZBrush-PCX
A complete technical comparison of X Bitmap (Legacy MIME Alias) and Pixologic ZBrush PCX — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.
Equal browser support
Feature Support
| Feature | XBM | ZBrush-PCX |
|---|---|---|
| Transparency (Alpha) | Yes | ✕ No |
| Animation Support | ✕ No | ✕ No |
| Progressive Loading | ✕ No | ✕ No |
| HDR Support | ✕ No | ✕ No |
| EXIF Metadata | ✕ No | ✕ No |
| ICC Color Profile | ✕ No | ✕ No |
X Bitmap (Legacy MIME Alias)
image/x-xbm
Extension
.xbm
Container
C Source Code Header (.h)
Compression
Uncompressed (Source Code)
Algorithm
None
Color Depth
1-bit (Monochrome)
Developed by
MIT / X Consortium (X Window System)
Released
1988
Magic Bytes
23 64 65 66 69 6e 65 (ASCII '#define')
Pixologic ZBrush PCX
image/vnd.zbrush.pcx
Extension
.pcx
Container
ZSoft PCX
Compression
Run-Length Encoding (RLE)
Algorithm
ZSoft Run-Length Encoding (RLE)
Color Depth
8-bit (Grayscale), 24-bit (RGB)
Developed by
ZSoft (Format) / Pixologic (MIME Registration)
Released
1985
Magic Bytes
0A 05 01 08
Browser Support Comparison
| Browser | XBM | ZBrush-PCX |
|---|---|---|
Chrome
|
✕ | ✕ |
Firefox
|
✕ | ✕ |
Safari
|
✕ | ✕ |
Edge
|
✕ | ✕ |
IE (Legacy)
|
✓
|
✕ |
XBM
XBM Strengths
- Can be compiled directly into C or C++ source code without needing an external file loader or binary asset manager
- Human-readable structure allows developers to inspect, edit, or hand-craft tiny icons directly within a text editor
- Extremely predictable and lightweight for 1-bit hardware displays and embedded systems
Limitations
- Strictly limited to 1-bit monochrome (black and white) graphics with no gray or color support
- Text-based C syntax creates massive file bloat compared to binary 1-bit formats like PBM
- Completely deprecated in modern web browsers and desktop GUI frameworks
ZBrush-PCX
ZBrush-PCX Strengths
- Extremely simple, lossless RLE compression makes it trivial to parse and encode programmatically
- Universally supported by almost every 2D image editor created since the 1990s
Limitations
- Completely obsolete for modern 3D workflows, which require 16-bit or 32-bit floating-point precision (like OpenEXR or TIFF) to avoid stepping artifacts in displacement maps
- No support for modern metadata (EXIF/XMP) or native alpha channels
- Zero native support in modern web browsers
When to choose which format
XBM
Use XBM when…
- X Window System (X11) Cursors and Icons
- Embedded C/C++ Firmware UI Assets
- Early 1990s Unix Web Graphics
ZBrush-PCX
Use ZBrush-PCX when…
- Legacy ZBrush Alpha Brushes
- 8-bit Grayscale Displacement Maps
- ZBrush Texture Exports