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Image MIME Reference
Alias-PIX

Alias PIX Image

image/x-alias-pix
VS

DirectDraw Surface

image/vnd.ms-dds
DDS

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

Equal browser support

Feature Support

Feature Alias-PIX DDS
Transparency (Alpha) ✕ No Yes
Animation Support ✕ No ✕ No
Progressive Loading ✕ No ✕ No
HDR Support ✕ No Yes
EXIF Metadata ✕ No ✕ No
ICC Color Profile ✕ No ✕ No
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 →
DirectDraw Surface
image/vnd.ms-dds
Extension
.dds
Container DirectDraw Surface
Compression Block Compression (BC1-BC7) / DXTC / S3TC / Uncompressed (RGBA, Floating-Point)
Algorithm
DXT1-DXT5BC1-BC7ASTC / ETC2 (Extended)
Color Depth 8-bit, 16-bit, 24-bit, 32-bit (RGBA), 16-bit/32-bit Floating Point (HDR)
Developed by Microsoft Corporation
Released 1999
Magic Bytes
44 44 53 20
Full DDS reference →

Browser Support Comparison

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  • Completely obsolete, having been replaced by more robust formats like TIFF, TGA, and EXR in modern 3D pipelines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

DDS Strengths

  • Massively reduces VRAM footprint and memory bandwidth usage because the GPU decodes the block compression in hardware
  • Encapsulates complex texture arrays, volume textures, cubemaps, and entire mipmap chains within a single, highly structured file
  • Supports high-dynamic-range (HDR) floating-point data for modern physically based rendering (PBR)
Limitations
  • Block compression algorithms (like DXT) are lossy and can introduce ugly blocky artifacts, especially in smooth gradients or normal maps if not tuned properly
  • Files are generally larger on the physical hard drive than highly compressed formats like PNG or WebP
  • Zero support in web browsers or standard consumer image viewers

When to choose which format

Alias-PIX
Use Alias-PIX when…
  • Legacy Alias PowerAnimator Textures
  • 1990s SGI Workstation Render Outputs
  • Historical 3D Graphics Archival
DDS
Use DDS when…
  • Real-Time 3D Game Textures
  • DirectX and Vulkan Rendering Pipelines
  • Skyboxes and Environment Cubemaps
  • Volume Textures (3D Textures)

More comparisons

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