移植opencv2.4.9到android过程记录

【移植opencv2.4.9到android过程记录】智者不为愚者谋，勇者不为怯者死。这篇文章主要讲述移植opencv2.4.9到android过程记录相关的知识，希望能为你提供帮助。
http://blog.csdn.net/brightming/article/details/50606463
在移植到arm开发板的时候已经说过，OpenCV已经为各平台准备了一套cmake交叉编译脚本。为Android移植的脚本在opencv目录/platforms/android/android.toolchain.cmake。
这个脚本里面有很详细的过程介绍，按照它里面的说明，配置好ndk的路径，就可以了。
但我们还需要实现其他目的：
1、使用fpu，neon,且Tag_FP_arch: VFPv4
2、动态库的形式编译
这些通过阅读android.toolchain.cmake文件，以及opencv目录下的CMakeLists.txt文件可以知道。例如关于abi的说明（在交叉编译脚本）：

# ABI-specific flags if( ARMEABI_V7A ) set( ANDROID_CXX_FLAGS "${ANDROID_CXX_FLAGS} -march=armv7-a -mfloat-abi=softfp" ) if( NEON ) set( ANDROID_CXX_FLAGS "${ANDROID_CXX_FLAGS} -mfpu=neon" ) elseif( VFPV3 ) set( ANDROID_CXX_FLAGS "${ANDROID_CXX_FLAGS} -mfpu=vfpv3" ) else() set( ANDROID_CXX_FLAGS "${ANDROID_CXX_FLAGS} -mfpu=vfpv3-d16" ) endif() elseif( ARMEABI_V6 ) set( ANDROID_CXX_FLAGS "${ANDROID_CXX_FLAGS} -march=armv6 -mfloat-abi=softfp -mfpu=vfp" ) # vfp == vfpv2 elseif( ARMEABI ) set( ANDROID_CXX_FLAGS "${ANDROID_CXX_FLAGS} -march=armv5te -mtune=xscale -msoft-float" ) endif()

看上面没有vfpv4的，先不更改了。
而关于编译动态库的，则在opencv/CMakeLists.txt内：

169 # OpenCV build components 170 # =================================================== 171 OCV_OPTION(BUILD_SHARED_LIBS"Build shared libraries (.dll/.so) instead of static ones (.lib/.a)" NOT (ANDROID OR ios) ) 172 OCV_OPTION(BUILD_opencv_apps"Build utility applications (used for example to train classifiers)" (NOT ANDROID) IF (NOT IOS) ) 173 OCV_OPTION(BUILD_ANDROID_EXAMPLES"Build examples for Android platform"ONIF ANDROID ) 174 OCV_OPTION(BUILD_DOCS"Create build rules for OpenCV Documentation" ON ) 175 OCV_OPTION(BUILD_EXAMPLES"Build all examples"OFF ) 176 OCV_OPTION(BUILD_PACKAGE"Enables ‘make package_source‘ command"ON ) 177 OCV_OPTION(BUILD_PERF_TESTS"Build performance tests"ONIF (NOT IOS) ) 178 OCV_OPTION(BUILD_TESTS"Build accuracy & regression tests"ONIF (NOT IOS) ) 179 OCV_OPTION(BUILD_WITH_DEBUG_INFO"Include debug info into debug libs (not MSCV only)" ON ) 180 OCV_OPTION(BUILD_WITH_STATIC_CRT"Enables use of staticaly linked CRT for staticaly linked OpenCV" ON IF MSVC ) 181 OCV_OPTION(BUILD_FAT_java_LIB"Create fat java wrapper containing the whole OpenCV library" ON IF NOT BUILD_SHARED_LIBS AND CMAKE_COMPILER_IS_GNUCXX ) 182 OCV_OPTION(BUILD_ANDROID_SERVICE"Build OpenCV Manager for Google Play" OFF IF ANDROID AND ANDROID_SOURCE_TREE ) 183 OCV_OPTION(BUILD_ANDROID_PACKAGE"Build platform-specific package for Google Play" OFF IF ANDROID )

执行cmake指令：

cmake -DCMAKE_INSTALL_PREFIX=../install_neon_dir -DCMAKE_BUILD_TYPE=RELEASE -DBUILD_SHARED_LIBS=1 -DCMAKE_TOOLCHAIN_FILE=../android.toolchain.cmake -DANDROID_ABI="armeabi-v7a with NEON" ../../../

可以看到结果为：

--C/C++: --Built as dynamic libs?:YES --C++ Compiler:/home/gumh/software/android-ndk-r9d/toolchains/arm-linux-androideabi-4.8/prebuilt/linux-x86_64/bin/arm-linux-androideabi-g++(ver 4.8) --C++ flags (Release):-fexceptions -frtti -Wno-psabi --sysroot=/home/gumh/software/android-ndk-r9d/platforms/android-8/arch-arm -fpic -funwind-tables -finline-limit=64 -fsigned-char -no-canonical-prefixes -march=armv7-a -mfloat-abi=softfp -mfpu=neon -fdata-sections -ffunction-sections -Wa,--noexecstack-fsigned-char -W -Wall -Werror=return-type -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wundef -Winit-self -Wpointer-arith -Wshadow -Wsign-promo -Wno-narrowing -Wno-delete-non-virtual-dtor -fdiagnostics-show-option -fomit-frame-pointer -mfpu=neon -mthumb -fomit-frame-pointer -fno-strict-aliasing -O3 -DNDEBUG-DNDEBUG --C++ flags (Debug):-fexceptions -frtti -Wno-psabi --sysroot=/home/gumh/software/android-ndk-r9d/platforms/android-8/arch-arm -fpic -funwind-tables -finline-limit=64 -fsigned-char -no-canonical-prefixes -march=armv7-a -mfloat-abi=softfp -mfpu=neon -fdata-sections -ffunction-sections -Wa,--noexecstack-fsigned-char -W -Wall -Werror=return-type -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wundef -Winit-self -Wpointer-arith -Wshadow -Wsign-promo -Wno-narrowing -Wno-delete-non-virtual-dtor -fdiagnostics-show-option -fomit-frame-pointer -mfpu=neon -marm -fno-omit-frame-pointer -fno-strict-aliasing -O0 -g -DDEBUG -D_DEBUG-O0 -DDEBUG -D_DEBUG --C Compiler:/home/gumh/software/android-ndk-r9d/toolchains/arm-linux-androideabi-4.8/prebuilt/linux-x86_64/bin/arm-linux-androideabi-gcc --C flags (Release):-fexceptions -Wno-psabi --sysroot=/home/gumh/software/android-ndk-r9d/platforms/android-8/arch-arm -fpic -funwind-tables -finline-limit=64 -fsigned-char -no-canonical-prefixes -march=armv7-a -mfloat-abi=softfp -mfpu=neon -fdata-sections -ffunction-sections -Wa,--noexecstack-fsigned-char -W -Wall -Werror=return-type -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes -Wundef -Winit-self -Wpointer-arith -Wshadow -Wno-narrowing -fdiagnostics-show-option -fomit-frame-pointer -mfpu=neon -mthumb -fomit-frame-pointer -fno-strict-aliasing -O3 -DNDEBUG-DNDEBUG --C flags (Debug):-fexceptions -Wno-psabi --sysroot=/home/gumh/software/android-ndk-r9d/platforms/android-8/arch-arm -fpic -funwind-tables -finline-limit=64 -fsigned-char -no-canonical-prefixes -march=armv7-a -mfloat-abi=softfp -mfpu=neon -fdata-sections -ffunction-sections -Wa,--noexecstack-fsigned-char -W -Wall -Werror=return-type -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes -Wundef -Winit-self -Wpointer-arith -Wshadow -Wno-narrowing -fdiagnostics-show-option -fomit-frame-pointer -mfpu=neon -marm -fno-omit-frame-pointer -fno-strict-aliasing -O0 -g -DDEBUG -D_DEBUG-O0 -DDEBUG -D_DEBUG --Linker flags (Release):-Wl,--fix-cortex-a8 -Wl,--no-undefined -Wl,--gc-sections -Wl,-z,noexecstack -Wl,-z,relro -Wl,-z,now --Linker flags (Debug):-Wl,--fix-cortex-a8 -Wl,--no-undefined -Wl,--gc-sections -Wl,-z,noexecstack -Wl,-z,relro -Wl,-z,now --Precompiled headers:YES

在arm的编译时，设置-mfpu是：-mfpu=neon-vfpv4，这里只是neon.
最后编译的结果为：

[[email protected] build_neon]$ readelf -a lib/armeabi-v7a/libopencv_core.so ... Attribute Section: aeabi File Attributes Tag_CPU_name: "ARM v7" Tag_CPU_arch: v7 Tag_CPU_arch_profile: Application Tag_ARM_ISA_use: Yes Tag_THUMB_ISA_use: Thumb-2 Tag_FP_arch: VFPv3 Tag_Advanced_SIMD_arch: NEONv1 Tag_ABI_PCS_wchar_t: 4 Tag_ABI_FP_denormal: Needed Tag_ABI_FP_exceptions: Needed Tag_ABI_FP_number_model: IEEE 754 Tag_ABI_align_needed: 8-byte Tag_ABI_enum_size: int Tag_ABI_HardFP_use: SP and DP Tag_ABI_optimization_goals: Aggressive Speed Tag_CPU_unaligned_access: v6 Tag_DIV_use: Not allowed