Interop 2026 JPEG XL Investigation

Scope

Features of JPEG XL that should be tested:

• High bit depth: Test for 8, 10, 12, and 16-bit depths.
• Wide gamut: Test Display P3, Adobe RGB, Rec.2020, ProPhoto RGB, etc.
• HDR: Test tone mapping (PQ/HLG) and gain maps (ISO 21496-1)
• ICC profiles: Test exotic/uncommon use of ICC profiles.
• CMYK: Test using the de-facto standard conversion between sRGB and CMYK.
• VarDCT: Test at least the largest and smallest block sizes, and smaller/larger than allowed by spec if the bitstream can express it.
• Modular mode: Test both lossy and lossless mode.
• Alpha channel: Test with VarDCT and modular mode.
• Progressive Rendering: Align on how browsers should render just the DC data, and whether to support progressive_dc which is even further downsampled.
• Lossless Transcoded JPEG: Test basic support.
• Orientation: Test that orientation in codestream is respected and EXIF orientation is ignored.
• Animations: Test basic support.
• Layers: Test basic support.
• JPEG XL art: Support for minimal JPEG XL files using modular mode to produce JPEG XL art (may be sensitive to minor differences in decoders)

Web integration points to test:

• <img>, <picture> & <source>
• <video poster>
• <input type=image>
• <embed>, <object> & <iframe>
• <link rel=preload as=image>
• SVG <image>
• CSS background-image, content, image-set(), list-style-image
• Canvas (2D, WebGL, WebGPU) including createImageBitmap() and Float16Array
• ImageDecoder API

Roadmap

• At least one test in https://wpt.fyi/results/jpegxl for each of the 14 features and 9 integration points listed above.
• Propose a solution (RFC) for testing HDR and wide gamut.

Scoring

• Scored linearly for the total number of features and integration points covered by tests. Tests that cannot be automated due to infrastructure limitations do not contribute to the score.