Parent Issue

Part of #74333

Summary

Add support for detecting and handling UltraHDR JPEG images (ISO 21496-1 gain map format) in the client-side media upload workflow.

Background

UltraHDR is a format that embeds HDR information (gain maps) within standard JPEG files, allowing HDR-capable displays to show enhanced dynamic range while maintaining backwards compatibility with SDR displays. This format is increasingly common from modern smartphone cameras (Google Pixel, Samsung Galaxy, etc.).

Implementation

• Detect UltraHDR images during upload using the open-ultrahdr npm package
• Automatically extract the SDR base image for storage, ensuring backwards compatibility
• The original UltraHDR file can be preserved for HDR display support

Acceptance Criteria

• UltraHDR JPEGs are detected during client-side upload
• Regular JPEGs continue to work normally
• No errors occur when uploading UltraHDR images
• ISO JPEG gain maps are detected during client-side upload
• All sub sized generated images retain ISO JPG gain maps by default
• JPEGs without a gain map continue to work normally
• No errors occur when uploading ISO JPEG gain map images

Technical Notes

• Uses open-ultrahdr npm package (wraps open-ultrahdr-wasm)
• WASM files are loaded as needed
• Processing happens client-side with no server requirements