Add tracking for "Ultra HDR JPG"

[gregbenz]

HDR image support is growing on the web and it will be important to understand which browsers and how widespread support is for HDR images.

Chrome Canary (on desktop and Android 14) now offer support for a gain map standard for HDR images as "Ultra HDR JPG". This format includes a secondary image and metadata to allow a single file to display in an optimal way on both SDR (standard dynamic rang) and HDR (high dynamic range) displays. https://developer.android.com/guide/topics/media/hdr-image-format
Adobe has published sample JPG gain map images at https://helpx.adobe.com/camera-raw/using/gain-map.html

This format is inherently backwards compatible with any browser which supports JPG, but only one which supports both HDR and the new gain map standard will be able to properly display the HDR content. I would propose tracking a list of browsers which properly interpret the gain map.

[gregbenz]

Related topic: HDR AVIF: #6504

[gregbenz]

JPG gain maps are now supported in 4 browsers (collectively ~75% of browsing if all clients were updated to latest):

• mainline Chrome v116 (via chrome://flags/#gainmap-hdr-images) - on desktop
  

• Chrome Canary v118 (via chrome://flags/#gainmap-hdr-images) on Android 14 beta
  

• Brave v1.57.47 (via brave://flags/#gainmap-hdr-images)
  

• Opera v101 (via opera://flags/#gainmap-hdr-images)
  

• MS Edge Canary v117 on Windows (no dev flag needed)