Free webp to jpg
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Image MIME Reference
APNG

Animated Portable Network Graphics

image/vnd.mozilla.apng
VS

Sigma X3F RAW Image

image/x-sigma-x3f
Sigma-X3F

A complete technical comparison of Animated Portable Network Graphics and Sigma X3F RAW Image — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

APNG wins on browser support

Feature Support

Feature APNG Sigma-X3F
Transparency (Alpha) Yes ✕ No
Animation Support Yes ✕ No
Progressive Loading Yes ✕ No
HDR Support ✕ No Yes
EXIF Metadata Yes Yes
ICC Color Profile Yes Yes
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 →
Sigma X3F RAW Image
image/x-sigma-x3f
Extension
.x3f
Container Foveon Proprietary Header
Compression Uncompressed / Proprietary Lossless
Algorithm
NoneFoveon Proprietary Huffman-based
Color Depth 12-bit (Per Channel), 14-bit (Per Channel)
Developed by Foveon, Inc. / Sigma Corporation
Released 2002
Magic Bytes
46 4F 56 62
Full Sigma-X3F reference →

Browser Support Comparison

Browser APNG Sigma-X3F
Chrome Chrome
✓ 59
 ✕
Firefox Firefox
✓ 3
 ✕
Safari Safari
✓ 8
 ✕
Edge Edge
✓ 79
 ✕
IE IE (Legacy)
✕ ✕
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)
Sigma-X3F

Sigma-X3F Strengths

  • Provides absolute per-pixel color accuracy without the interpolation artifacts or moiré patterns typical of Bayer-sensor RAW files
  • Unique 'FOVb' magic byte signature prevents accidental misidentification by standard file sniffers, unlike many TIFF-based raw formats
  • Incredible sharpness and detail resolution at the raw sensor level
Limitations
  • Decoding is extremely computationally expensive and completely proprietary, meaning third-party software often struggles to match the color science of Sigma's own (famously slow) Photo Pro application
  • Massive file sizes because it records three complete RGB channels for every single spatial pixel coordinate
  • Zero support in web browsers or standard OS image viewers

When to choose which format

APNG
Use APNG when…
  • High-Quality Web Animations
  • Stickers (Apple iMessage, LINE, Discord)
  • UI Loaders with Alpha Transparency
  • GIF Replacement
Sigma-X3F
Use Sigma-X3F when…
  • Professional Digital Photography
  • Sigma / Foveon High-Acuity Imaging
  • Non-destructive RAW Post-Processing

More comparisons

APNG vs ACES → Sigma-X3F vs ACES → APNG vs AVCI → Sigma-X3F vs AVCI → APNG vs AVCS → Sigma-X3F vs AVCS → APNG vs AVIF → Sigma-X3F vs AVIF → All comparisons →
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