Android Studio 下通过 CMake 配置编译 libyuv 库

参考链接

创建 AS 工程，选择 Native C++，之后默认配置就可以了 （ps: 我工程的名字也取名为 libyuv 了，你们随意）

libyuv 的源码下载下来以后，放到 src/main/cpp 目录下

 修改 src/main/cpp 目录下的 CMakeList.txt

# For more information about using CMake with Android Studio, read the
# documentation: https://d.android.com/studio/projects/add-native-code.html

# Sets the minimum version of CMake required to build the native library.

cmake_minimum_required(VERSION 3.4.1)

include_directories(/home/lingyun/Projects/AndroidStudioProjects/libyuv/app/src/main/cpp/libyuv/include) # 重点，根据自己的路径进行修改
add_subdirectory(/home/lingyun/Projects/AndroidStudioProjects/libyuv/app/src/main/cpp/libyuv) # 重点

# Creates and names a library, sets it as either STATIC
# or SHARED, and provides the relative paths to its source code.
# You can define multiple libraries, and CMake builds them for you.
# Gradle automatically packages shared libraries with your APK.

add_library( # Sets the name of the library.
        native-lib

        # Sets the library as a shared library.
        SHARED

        # Provides a relative path to your source file(s).
        native-lib.cpp)

# Searches for a specified prebuilt library and stores the path as a
# variable. Because CMake includes system libraries in the search path by
# default, you only need to specify the name of the public NDK library
# you want to add. CMake verifies that the library exists before
# completing its build.

find_library( # Sets the name of the path variable.
        log-lib

        # Specifies the name of the NDK library that
        # you want CMake to locate.
        log)

# Specifies libraries CMake should link to your target library. You
# can link multiple libraries, such as libraries you define in this
# build script, prebuilt third-party libraries, or system libraries.

target_link_libraries( # Specifies the target library.
        native-lib

        # Links the target library to the log library
        # included in the NDK.
        ${log-lib}
        yuv) # 重点

然后再修改 libyuv 库的 CMakeList.txt (去掉一些编译生成的文件，也可以不改，按自己需要编辑)

# CMakeLists for libyuv
# Originally created for "roxlu build system" to compile libyuv on windows
# Run with -DTEST=ON to build unit tests

PROJECT ( YUV C CXX )   # "C" is required even for C++ projects
CMAKE_MINIMUM_REQUIRED( VERSION 2.8 )
OPTION( TEST "Built unit tests" OFF )

SET ( ly_base_dir   ${PROJECT_SOURCE_DIR} )
SET ( ly_src_dir    ${ly_base_dir}/source )
SET ( ly_inc_dir    ${ly_base_dir}/include )
SET ( ly_tst_dir    ${ly_base_dir}/unit_test )
SET ( ly_lib_name   yuv )
SET ( ly_lib_static ${ly_lib_name} )
SET ( ly_lib_shared ${ly_lib_name}_shared )

FILE ( GLOB_RECURSE ly_source_files ${ly_src_dir}/*.cc )
LIST ( SORT         ly_source_files )

FILE ( GLOB_RECURSE ly_unittest_sources ${ly_tst_dir}/*.cc )
LIST ( SORT         ly_unittest_sources )

INCLUDE_DIRECTORIES( BEFORE ${ly_inc_dir} )

# this creates the static library (.a)
ADD_LIBRARY             ( ${ly_lib_static} STATIC ${ly_source_files} )

# this creates the shared library (.so)
ADD_LIBRARY             ( ${ly_lib_shared} SHARED ${ly_source_files} )
SET_TARGET_PROPERTIES   ( ${ly_lib_shared} PROPERTIES OUTPUT_NAME "${ly_lib_name}" )
SET_TARGET_PROPERTIES   ( ${ly_lib_shared} PROPERTIES PREFIX "lib" )

# this creates the conversion tool
#ADD_EXECUTABLE         ( yuvconvert ${ly_base_dir}/util/yuvconvert.cc )
#TARGET_LINK_LIBRARIES  ( yuvconvert ${ly_lib_static} )


INCLUDE ( FindJPEG )
if (JPEG_FOUND)
  include_directories( ${JPEG_INCLUDE_DIR} )
  target_link_libraries( yuvconvert ${JPEG_LIBRARY} )
  add_definitions( -DHAVE_JPEG )
endif()

if(TEST)
  find_library(GTEST_LIBRARY gtest)
  if(GTEST_LIBRARY STREQUAL "GTEST_LIBRARY-NOTFOUND")
    set(GTEST_SRC_DIR /usr/src/gtest CACHE STRING "Location of gtest sources")
    if(EXISTS ${GTEST_SRC_DIR}/src/gtest-all.cc)
      message(STATUS "building gtest from sources in ${GTEST_SRC_DIR}")
      set(gtest_sources ${GTEST_SRC_DIR}/src/gtest-all.cc)
      add_library(gtest STATIC ${gtest_sources})
      include_directories(${GTEST_SRC_DIR})
      include_directories(${GTEST_SRC_DIR}/include)
      set(GTEST_LIBRARY gtest)
    else()
      message(FATAL_ERROR "TEST is set but unable to find gtest library")
    endif()
  endif()

  add_executable(libyuv_unittest ${ly_unittest_sources})
  target_link_libraries(libyuv_unittest ${ly_lib_name} ${GTEST_LIBRARY})
  find_library(PTHREAD_LIBRARY pthread)
  if(NOT PTHREAD_LIBRARY STREQUAL "PTHREAD_LIBRARY-NOTFOUND")
    target_link_libraries(libyuv_unittest pthread)
  endif()
  if (JPEG_FOUND)
    target_link_libraries(libyuv_unittest ${JPEG_LIBRARY})
  endif()

  if(NACL AND NACL_LIBC STREQUAL "newlib")
    target_link_libraries(libyuv_unittest glibc-compat)
  endif()

  find_library(GFLAGS_LIBRARY gflags)
  if(NOT GFLAGS_LIBRARY STREQUAL "GFLAGS_LIBRARY-NOTFOUND")
    target_link_libraries(libyuv_unittest gflags)
    add_definitions(-DLIBYUV_USE_GFLAGS)
  endif()
endif()


# install the conversion tool, .so, .a, and all the header files
#INSTALL ( PROGRAMS ${CMAKE_BINARY_DIR}/yuvconvert         DESTINATION bin )
#INSTALL ( TARGETS ${ly_lib_static}                        DESTINATION lib )
#INSTALL ( TARGETS ${ly_lib_shared} LIBRARY                DESTINATION lib RUNTIME DESTINATION bin )
INSTALL ( DIRECTORY ${PROJECT_SOURCE_DIR}/include/     DESTINATION include )

# create the .deb and .rpm packages using cpack
#INCLUDE ( CM_linux_packages.cmake )

YuvUtils.java

package com.example.libyuv;


public class YuvUtils {

    static {
        System.loadLibrary("native-lib");
    }

    // 创建一个YuvUtils，有三个常用的方法，第一个就是NV21转I420，然后旋转I420，最后一个是NV21转换I420并顺时针旋转90度，可以替换前两个方法
    public static native void NV21ToI420(byte[] input, byte[] output, int width, int height);
    public static native void RotateI420(byte[] input, byte[] output, int width, int height, int rotation);
    public static native void NV21ToI420andRotate90Clockwise(byte[] input, byte[] output, int width, int height);
}

native-lib.cpp

#include <jni.h>
#include <string>
#include <cstring>
#include <android/log.h>

#include "libyuv/include/libyuv.h"

#define LOG_TAG "libyuv"
#define LOGV(...)  __android_log_print(ANDROID_LOG_VERBOSE, LOG_TAG, __VA_ARGS__)
#define LOGD(...)  __android_log_print(ANDROID_LOG_DEBUG, LOG_TAG, __VA_ARGS__)
#define LOGI(...)  __android_log_print(ANDROID_LOG_INFO, LOG_TAG, __VA_ARGS__)
#define LOGE(...)  __android_log_print(ANDROID_LOG_ERROR, LOG_TAG, __VA_ARGS__)

using namespace libyuv;

extern "C" JNIEXPORT jstring JNICALL
Java_com_example_libyuv_MainActivity_stringFromJNI(
        JNIEnv *env,
        jobject /* this */) {
    std::string hello = "Hello from C++";
    return env->NewStringUTF(hello.c_str());
}

extern "C"
JNIEXPORT void JNICALL
Java_com_example_libyuv_YuvUtils_NV21ToI420(JNIEnv *env, jobject instance, jbyteArray input_,
                                            jbyteArray output_, jint in_width, jint in_height) {
    jbyte *srcData = env->GetByteArrayElements(input_, NULL);
    jbyte *dstData = env->GetByteArrayElements(output_, NULL);

    NV21ToI420((const uint8_t *) srcData, in_width,
               (uint8_t *) srcData + (in_width * in_height), in_width,
               (uint8_t *) dstData, in_width,
               (uint8_t *) dstData + (in_width * in_height), in_width / 2,
               (uint8_t *) dstData + (in_width * in_height * 5 / 4), in_width / 2,
               in_width, in_height);
    env->ReleaseByteArrayElements(input_, srcData, 0);
    env->ReleaseByteArrayElements(output_, dstData, 0);
}

extern "C"
JNIEXPORT void JNICALL
Java_com_example_libyuv_YuvUtils_RotateI420(JNIEnv *env, jobject type, jbyteArray input_,
                                            jbyteArray output_, jint in_width, jint in_height,
                                            jint rotation) {
    jbyte *srcData = env->GetByteArrayElements(input_, NULL);
    jbyte *dstData = env->GetByteArrayElements(output_, NULL);


    RotationMode rotationMode = kRotate0;
    switch (rotation) {
        case 90:
            rotationMode = kRotate90;
            break;
        case 180:
            rotationMode = kRotate180;
            break;
        case 270:
            rotationMode = kRotate270;
            break;
    }
    I420Rotate((const uint8_t *) srcData, in_width,
               (uint8_t *) srcData + (in_width * in_height), in_width / 2,
               (uint8_t *) srcData + (in_width * in_height * 5 / 4), in_width / 2,
               (uint8_t *) dstData, in_height,
               (uint8_t *) dstData + (in_width * in_height), in_height / 2,
               (uint8_t *) dstData + (in_width * in_height * 5 / 4), in_height / 2,
               in_width, in_height,
               rotationMode);

    env->ReleaseByteArrayElements(input_, srcData, 0);
    env->ReleaseByteArrayElements(output_, dstData, 0);
}

extern "C"
JNIEXPORT void JNICALL
Java_com_example_libyuv_YuvUtils_NV21ToI420andRotate90Clockwise(JNIEnv *env, jobject type,
                                                                jbyteArray input_,
                                                                jbyteArray output_,
                                                                jint in_width, jint in_height) {
    jbyte *srcData = env->GetByteArrayElements(input_, NULL);
    jbyte *dstData = env->GetByteArrayElements(output_, NULL);
    jsize size = env->GetArrayLength(input_);

    NV21ToI420((const uint8_t *) srcData, in_width,
               (uint8_t *) srcData + (in_width * in_height), in_width,
               (uint8_t *) dstData, in_width,
               (uint8_t *) dstData + (in_width * in_height), in_width / 2,
               (uint8_t *) dstData + (in_width * in_height * 5 / 4), in_width / 2,
               in_width, in_height);

    I420Rotate((const uint8_t *) dstData, in_width,
               (uint8_t *) dstData + (in_width * in_height), in_width / 2,
               (uint8_t *) dstData + (in_width * in_height * 5 / 4), in_width / 2,
               (uint8_t *) srcData, in_height,
               (uint8_t *) srcData + (in_width * in_height), in_height / 2,
               (uint8_t *) srcData + (in_width * in_height * 5 / 4), in_height / 2,
               in_width, in_height,
               kRotate90);
    memcpy(dstData, srcData, size);

//    fixme can't work
//    ConvertToI420((const uint8_t *) srcData, size,
//                  (uint8_t *)dstData, in_width,
//                  (uint8_t *)dstData + (in_width * in_height), in_width / 2,
//                  (uint8_t *)dstData + (in_width * in_height * 5 / 4), in_width / 2,
//                  0, 0,
//                  in_width, in_height,
//                  in_width, in_height,
//                  kRotate90,
//                  FOURCC_NV21);
//
//   fixme can't work
//    NV12ToI420Rotate((const uint8_t *) srcData, in_width,
//                     (uint8_t *) srcData + (in_width * in_height), in_width,
//                     (uint8_t *)dstData, in_width,
//                     (uint8_t *)dstData + (in_width * in_height * 5 / 4), in_width / 2,
//                     (uint8_t *)dstData + (in_width * in_height), in_width / 2,
//                     in_width, in_height,
//                     kRotate90);

    env->ReleaseByteArrayElements(input_, srcData, 0);
    env->ReleaseByteArrayElements(output_, dstData, 0);
}

build 生成的 so：

不过这个方法有个问题，就是没有把 neon 优化的代码编译进来，需要自己手动修改 CMakeList.txt，或者使用 .mk 的方式(参考0， 参考1，参考2)，亦或者通过 libyuv 的官网的方法进行编译。

根据 CMakeList 的方式（启用了 neon ）编译出来的大小为 200 多 KB （只测试了 Debug）

根据 mk 的方式编译出来的 libyuv.so 的大小也为 200多 KB  (只测试了 Debug)