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Image MIME Reference
FITS

Flexible Image Transport System

image/fits
VS

JPEG 2000 Codestream

image/j2c
J2C

A complete technical comparison of Flexible Image Transport System and JPEG 2000 Codestream — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

Equal browser support

Feature Support

Feature FITS J2C
Transparency (Alpha) ✕ No Yes
Animation Support ✕ No ✕ No
Progressive Loading ✕ No Yes
HDR Support Yes Yes
EXIF Metadata ✕ No ✕ No
ICC Color Profile ✕ No ✕ No
Flexible Image Transport System
image/fits
Extension
.fits.fit.fts
Container FITS
Compression Uncompressed / Tile Compressed (Rice, GZIP)
Algorithm
UncompressedRiceGZIPHcompress
Color Depth 8-bit, 16-bit, 32-bit, 64-bit (Float/Double)
Developed by IAU FITS Working Group / NASA
Released 1981
Magic Bytes
53 49 4D 50 4C 45 20 20 3D 20
Full FITS reference →
JPEG 2000 Codestream
image/j2c
Extension
.j2c.j2k.jpc
Container None (Raw Bitstream)
Compression JPEG 2000 (Discrete Wavelet Transform) / Lossless / Lossy
Algorithm
Discrete Wavelet Transform (DWT)
Color Depth 8-bit, 10-bit, 12-bit, 16-bit (Per Channel)
Developed by Joint Photographic Experts Group (JPEG)
Released 2000
Magic Bytes
FF 4F FF 51
Full J2C reference →

Browser Support Comparison

Browser FITS J2C
Chrome Chrome
✕ ✕
Firefox Firefox
✕ ✕
Safari Safari
✕ ✕
Edge Edge
✕ ✕
IE IE (Legacy)
✕ ✕
FITS

FITS Strengths

  • The undisputed global standard for archiving and sharing astronomical data
  • Self-documenting: Headers are written in plain ASCII, ensuring data is readable decades later regardless of software
  • Supports incredibly high dynamic range, N-dimensional arrays, and complex binary tables
Limitations
  • No support in standard consumer software or web browsers
  • Uncompressed raw FITS files from modern telescopes can be excessively large
  • Does not use standard metadata models like EXIF or XMP, requiring specialized parsers
J2C

J2C Strengths

  • Provides state-of-the-art wavelet compression for high-end professional workflows (Digital Cinema)
  • Allows for highly efficient progressive decoding (by resolution or quality layer) natively within the stream
  • Supports lossless mathematical compression and high bit-depths (up to 16-bit per channel) natively
Limitations
  • Lacks a standard container to store color space info or metadata, requiring external systems (like MXF or DICOM) to map colors correctly
  • Extremely computationally expensive to encode and decode compared to standard DCT-based JPEG
  • Zero web browser support

When to choose which format

FITS
Use FITS when…
  • Astronomy & Astrophysics
  • Space Telescope Data (Hubble, JWST)
  • Scientific Data Archiving
  • Spectroscopy
J2C
Use J2C when…
  • Digital Cinema Packages (DCP)
  • Medical Imaging (DICOM Payloads)
  • Professional Broadcast and Archiving
  • Embedded Hardware Encoding

More comparisons

FITS vs ACES → J2C vs ACES → FITS vs APNG → J2C vs APNG → FITS vs AVCI → J2C vs AVCI → FITS vs AVCS → J2C vs AVCS → FITS vs AVIF → J2C vs AVIF → All comparisons →
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