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)
