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Image MIME Reference
HSJ2

JPEG 2000 Image Sequence (Obsolete)

image/hsj2
VS

Truevision TGA (Legacy MIME Alias)

image/x-tga
TGA

A complete technical comparison of JPEG 2000 Image Sequence (Obsolete) and Truevision TGA (Legacy MIME Alias) — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

Equal browser support

Feature Support

Feature HSJ2 TGA
Transparency (Alpha) Yes Yes
Animation Support Yes ✕ No
Progressive Loading Yes ✕ No
HDR Support Yes ✕ No
EXIF Metadata Yes ✕ No
ICC Color Profile Yes ✕ No
JPEG 2000 Image Sequence (Obsolete)
image/hsj2
Extension
.hsj2
Container HEIF / ISOBMFF (ISO/IEC 15444-16 Obsolete)
Compression Lossy / Lossless
Algorithm
Motion JPEG 2000 (ISO/IEC 15444-3)
Color Depth 8-bit, 10-bit, 12-bit, 16-bit
Developed by ISO/IEC JTC 1 / ITU-T
Released 2019
Magic Bytes
XX XX XX XX 66 74 79 70 68 73 6A 32
Full HSJ2 reference →
Truevision TGA (Legacy MIME Alias)
image/x-tga
Extension
.tga.icb.vda.vst
Container Truevision TGA Footer/Header
Compression Uncompressed / Run-Length Encoding (RLE)
Algorithm
NoneRLE
Color Depth 8-bit (Grayscale or Indexed), 16-bit (High Color), 24-bit (True Color), 32-bit (True Color with Alpha Channel)
Developed by Truevision Inc.
Released 1984
Magic Bytes
54 52 55 45 56 49 53 49 4F 4E 2D 58 46 49 4C 45 2E 00 (At the end of the file)
Full TGA reference →

Browser Support Comparison

Browser HSJ2 TGA
Chrome Chrome
✕ ✕
Firefox Firefox
✕ ✕
Safari Safari
✕ ✕
Edge Edge
✕ ✕
IE IE (Legacy)
✕ ✕
HSJ2

HSJ2 Strengths

  • Historically attempted to combine Motion JPEG 2000 sequences with the flexible metadata capabilities of the HEIF container
  • Supported mathematically lossless compression and scalable wavelet decoding
Limitations
  • Officially deprecated by the standardization body (ISO/IEC JTC 1)
  • Completely superseded by image/hej2k, rendering hsj2 files obsolete for any new development or archiving
  • Zero web browser compatibility and negligible modern software support
TGA

TGA Strengths

  • Incredibly simple byte layout allows developers to write custom loaders and exporters in a few dozen lines of code, bypassing the need for heavy external libraries
  • Native support for 8-bit alpha channels ensures flawless transparency masking for real-time 3D rendering
  • Fast, predictable RLE decoding requires almost no CPU overhead compared to DEFLATE (PNG) or DCT (JPEG)
Limitations
  • RLE compression is relatively weak by modern standards, resulting in large file sizes
  • Lacks a standard magic byte header at the beginning of the file, making file-sniffing unreliable for older v1.0 files
  • Zero support in web browsers; must be converted to PNG or WebP for web delivery

When to choose which format

HSJ2
Use HSJ2 when…
  • Legacy Archival
  • Deprecated Workflows
TGA
Use TGA when…
  • Video Game 3D Textures and Materials
  • 3D Rendering and Animation Sequences
  • Legacy Video Production Workflows

More comparisons

HSJ2 vs ACES → TGA vs ACES → HSJ2 vs APNG → TGA vs APNG → HSJ2 vs AVCI → TGA vs AVCI → HSJ2 vs AVCS → TGA vs AVCS → HSJ2 vs AVIF → TGA vs AVIF → All comparisons →
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