commit	be53c5794e5db5ffe3669ca16b27d0daa97a094b	[log] [tgz]
author	Android Build Coastguard Worker <[email protected]>	Sat Dec 02 02:07:41 2023 +0000
committer	Android Build Coastguard Worker <[email protected]>	Sat Dec 02 02:07:41 2023 +0000
tree	f4ccb049b732c195a54810c3113449d664a784ce
parent	7f6fe3262672a9cbc38e3209026838069ebafbb6 [diff]
parent	5d7f30ac00a5b92fca6656629c995cc0fd0087f4 [diff]

tree: f4ccb049b732c195a54810c3113449d664a784ce

README.md

Background

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 parsing 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.

More information about libultrahdr can be found at https://developer.android.com/guide/topics/media/platform/hdr-image-format.

Building libultrahdr

libultrahdr compresses base image and gain map image in to jpeg format. For this libjpeg-turbo is used. This is cloned from https://github.com/libjpeg-turbo/libjpeg-turbo.git and included in the build process.

Requirements

CMake v3.13 or later
NASM or Yasm (If libjpeg-turbo needs to be built with SIMD extensions)
- If using NASM, 2.13 or later is required.
- If using Yasm, 1.2.0 or later is required.
- If building on macOS, NASM or Yasm can be obtained from MacPorts or Homebrew.
Compilers with support for C++17

Should work with GCC v7 (or later) and Clang 5 (or later) on Linux and Mac Platforms.

Should work with Microsoft Visual C++ 2019 (or later) on Windows Platforms.

Build Procedure

To build libultrahdr, examples, unit tests:

Un*x (including Linux, Mac)

mkdir {build_directory}
cd {build_directory}
cmake -G "Unix Makefiles"  -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++ -DUHDR_BUILD_TESTS=1 ../
make
ctest

This will generate the following files under {build_directory}:

libultrahdr.a
Static link library for the ultrahdr API

ultrahdr_app
Sample application demonstrating ultrahdr API

ultrahdr_unit_test
Unit tests

Visual C++ (IDE)

mkdir {build_directory}
cd {build_directory}
cmake -G "Visual Studio 16 2019" -DUHDR_BUILD_TESTS=1 ../
cmake --build ./ --config=Release
ctest -C Release

This will generate the following files under {build_directory/Release}:

ultrahdr.lib
Static link library for the ultrahdr API

ultrahdr_app.exe
Sample application demonstrating ultrahdr API

ultrahdr_unit_test.exe
Unit tests

Visual C++ (Command line)

mkdir {build_directory}
cd {build_directory}
cmake -G "NMake Makefiles" -DUHDR_BUILD_TESTS=1 ../
cmake --build ./
ctest

This will generate the following files under {build_directory}:

ultrahdr.lib
Static link library for the ultrahdr API

ultrahdr_app.exe
Sample application demonstrating ultrahdr API

ultrahdr_unit_test.exe
Unit tests

MinGW

NOTE: This assumes that you are building on a Windows machine using the MSYS environment.

mkdir {build_directory}
cd {build_directory}
cmake -G "MSYS Makefiles" -DUHDR_BUILD_TESTS=1 ../
cmake --build ./
ctest

mkdir {build_directory}
cd {build_directory}
cmake -G "MinGW Makefiles" -DUHDR_BUILD_TESTS=1 ../
cmake --build ./
ctest

This will generate the following files under {build_directory}:

libultrahdr.a
Static link library for the ultrahdr API

ultrahdr_app.exe
Sample application demonstrating ultrahdr API

ultrahdr_unit_test.exe
Unit tests

NOTE: To not build unit tests, skip passing -DUHDR_BUILD_TESTS=1

Building Fuzzers

Refer to README.md for complete instructions.

Using libultrahdr

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

Refer to jpegr.h for detailed description of various encode and decode api.
Refer to ultrahdr_app.cpp for examples of its usage.