MetalEDR-iOS

Demo of using Metal to render EDR/HDR content on iOS platform.

How it works

This demo uses a hack to activate EDR display on iOS platform:

• By setting up an invisible AVPlayerLayer, and plays short HDR video clip in the backgrond
• inspired by https://github.com/kiding/wanna-see-a-whiter-white

Then we can use Metal with a Float Point pixel format to output EDR contents.

Limitation

The "EDR trigger" hack basically has the same effect with metalLayer.wantsExtendedDynamicRangeContent = YES;,

But we still missing APIs like -[NSScreen maximumExtendedDynamicRangeColorComponentValue], so it's very hard to apply appropriate tone-mapping within Metal rendering process.

This demo outputs the raw pixel values loaded by CoreGraphics without applying any tone-mapping, so the colors will clip at current EDR max value and may seems off.

Credit

• Inspired by:
  • https://kidi.ng/wanna-see-a-whiter-white/
• HDR Video (EDR Trigger):
  • https://github.com/kiding/wanna-see-a-whiter-white
• HDR Image Resources:
  • https://github.com/AcademySoftwareFoundation/openexr-images/tree/master/TestImages
• Some sample code from:
  • https://developer.apple.com/wwdc21/10161
  • https://developer.apple.com/documentation/metal/using_a_render_pipeline_to_render_primitives?language=objc