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android/platform/external/libultrahdr/e432c4d93ded76d0eaead27b9e4636a85e67672b
commit
e432c4d93ded76d0eaead27b9e4636a85e67672b
[log]
author
Ram Mohan M <[email protected]>
Sun Oct 06 22:25:16 2024 +0530
committer
DichenZhang1 <[email protected]>
Wed Oct 16 12:01:48 2024 -0700
tree
fc489a8882a0acbcd9308cfc7376d54f5207bc0b
parent
8f894f7250de1f18b8fa09f0c1513255be190e8c [diff]
add API to set mastering display, target display peak brightness

For HLG, the brightness level of the maximum code value is not absolute.
This corresponds to the mastering display peak luminance. Also for
linear hdr intent inputs, as the inputs are normalized, there is no
accurate way to estimate the brightness level of the maximum code value.
This change introduces API to set mastering display peak luminance.

The target display peak luminance need not be always mastering display
peak luminance. Even if the content is mastered on a brighter display,
apps can configure desiredHeadRoom to avoid tonemapping on less capable
displays.

Test: ./ultrahdr_api
12 files changed
tree: fc489a8882a0acbcd9308cfc7376d54f5207bc0b
  1. .github/
  2. adobe-hdr-gain-map-license/
  3. benchmark/
  4. cmake/
  5. docs/
  6. examples/
  7. fuzzer/
  8. java/
  9. lib/
  10. tests/
  11. third_party/
  12. .clang-format
  13. Android.bp
  14. CMakeLists.txt
  15. LICENSE
  16. README.md
  17. ultrahdr_api.h
README.md

Introduction

libultrahdr is an image compression library that uses gain map technology to store and distribute HDR images. Conceptually on the encoding side, the library accepts SDR and HDR rendition of an image and from these a Gain Map (quotient between the two renditions) is computed. The library then uses backward compatible means to store the base image (SDR), gain map image and some associated metadata. Legacy readers that do not support handling the gain map image and/or metadata, will display the base image. Readers that support the format combine the base image with the gain map and render a high dynamic range image on compatible displays.

For additional information, see android hdr-image-format guide.

Build from source using CMake

This software suite has been built and tested on platforms:

  • Android
  • Linux
  • macOS
  • Windows

Refer to building.md for complete instructions.

Using libultrahdr

A detailed description of libultrahdr encode and decode api is included in ultrahdr_api.h and for sample usage refer demo app.

libultrahdr includes two classes of APIs, one to compress and the other to decompress HDR images:

Encoding api outline:

ScenarioHdr intent rawSdr intent rawSdr intent compressedGain map compressedQualityExifUse Case
API - 0P010 or rgb1010102NoNoNoOptionalOptionalUsed if, only hdr raw intent is present. [^1]
API - 1P010 or rgb1010102YUV420 or rgba8888NoNoOptionalOptionalUsed if, hdr raw and sdr raw intents are present.[^2]
API - 2P010 or rgb1010102YUV420 or rgba8888YesNoNoNoUsed if, hdr raw, sdr raw and sdr compressed intents are present.[^3]
API - 3P010 or rgb1010102NoYesNoNoNoUsed if, hdr raw and sdr compressed intents are present.[^4]
API - 4NoNoYesYesNoNoUsed if, sdr compressed, gain map compressed and GainMap Metadata are present.[^5]

[^1]: Tonemap hdr to sdr. Compute gain map from hdr and sdr. Compress sdr and gainmap at quality configured. Add exif if provided. Combine sdr compressed, gainmap in multi picture format with gainmap metadata. [^2]: Compute gain map from hdr and sdr. Compress sdr and gainmap at quality configured. Add exif if provided. Combine sdr compressed, gainmap in multi picture format with gainmap metadata. [^3]: Compute gain map from hdr and raw sdr. Compress gainmap. Combine sdr compressed, gainmap in multi picture format with gainmap metadata. [^4]: Decode compressed sdr input. Compute gain map from hdr and decoded sdr. Compress gainmap. Combine sdr compressed, gainmap in multi picture format with gainmap metadata. [^5]: Combine sdr compressed, gainmap in multi picture format with gainmap metadata.

Decoding api outline:

Configure display device characteristics (display transfer characteristics, max display boost) for optimal usage.

InputUsage
max_display_boost(optional, >= 1.0) the maximum available boost supported by a display.
supported color transfer format pairscolor transferColor format SDR32bppRGBA8888HDR_LINEAR64bppRGBAHalfFloatHDR_PQ32bppRGBA1010102 PQHDR_HLG32bppRGBA1010102 HLG