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Image MIME Reference
Alias-PIX

Alias PIX Image

image/x-alias-pix
VS

Animated Portable Network Graphics

image/vnd.mozilla.apng
APNG

A complete technical comparison of Alias PIX Image and Animated Portable Network Graphics — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

APNG wins on browser support

Feature Support

Feature Alias-PIX APNG
Transparency (Alpha) ✕ No Yes
Animation Support ✕ No Yes
Progressive Loading ✕ No Yes
HDR Support ✕ No ✕ No
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)
Full Alias-PIX reference →
Animated Portable Network Graphics
image/vnd.mozilla.apng
Extension
.apng.png
Container PNG Chunk Stream
Compression Deflate (Lossless)
Algorithm
Deflate (zlib)
Color Depth 8-bit (Indexed), 24-bit (TrueColor), 32-bit (RGBA)
Developed by Mozilla Corporation (Stuart Parmenter & Vladimir Vukićević)
Released 2004
Magic Bytes
89 50 4E 47 0D 0A 1A 0A
Full APNG reference →

Browser Support Comparison

Browser Alias-PIX APNG
Chrome Chrome
✕
✓ 59
Firefox Firefox
✕
✓ 3
Safari Safari
✕
✓ 8
Edge Edge
✕
✓ 79
IE 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  • Completely obsolete, having been replaced by more robust formats like TIFF, TGA, and EXR in modern 3D pipelines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
APNG

APNG Strengths

  • Supports 8-bit alpha transparency, completely solving the ugly 'white halo' problem inherent to GIFs
  • Gracefully degrades; viewers that do not support APNG will render a perfectly valid, static PNG of the first frame
  • Provides lossless compression that retains absolute pixel-perfect quality for UI elements and line art
Limitations
  • Because it relies on lossless Deflate compression, file sizes for complex, video-like animations can be massive compared to lossy formats like WebP or AVIF
  • Was initially rejected by the official PNG group, delaying its adoption for nearly a decade
  • Lacks native hardware decoding acceleration, unlike video-based animated formats (like MP4 or WebM)

When to choose which format

Alias-PIX
Use Alias-PIX when…
  • Legacy Alias PowerAnimator Textures
  • 1990s SGI Workstation Render Outputs
  • Historical 3D Graphics Archival
APNG
Use APNG when…
  • High-Quality Web Animations
  • Stickers (Apple iMessage, LINE, Discord)
  • UI Loaders with Alpha Transparency
  • GIF Replacement

More comparisons

Alias-PIX vs ACES → APNG vs ACES → Alias-PIX vs AVCI → APNG vs AVCI → Alias-PIX vs AVCS → APNG vs AVCS → Alias-PIX vs AVIF → APNG vs AVIF → All comparisons →
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