我尝试为Android构建OpenCV 4.5.1 SDK，因为我需要带有contrib模块的SDK，而官方发布的[1]只有标准模块。但我构建的库几乎大了10倍，例如：libopencv_core.a==>47.6 MB自行编译，5.3 MB来自官方存储库(均用于arm64-v8a(
这是我的cmake命令，后面是用于编译的ninja。
cmake
-DCMAKE_TOOLCHAIN_FILE=$ANDROID_NDK/build/cmake/android.toolchain.cmake
-DANDROID_ABI=$ABI
-DANDROID_NATIVE_API_LEVEL=$ANDROID_PLATFORM
-GNinja
-DOPENCV_EXTRA_MODULES_PATH=../opencv_contrib/modules
-DCMAKE_BUILD_TYPE:STRING=Release
-DBUILD_TESTS=FALSE -DBUILD_PERF_TESTS=FALSE
-DBUILD_ANDROID_EXAMPLES=FALSE
-DCMAKE_CONFIGURATION_TYPES:STRING=Release
-DCMAKE_CXX_FLAGS_RELEASE:STRING=-Os
-DCMAKE_C_FLAGS_RELEASE:STRING=-Os
-DBUILD_opencv_highgui:BOOL=OFF
-DBUILD_opencv_js_bindings_generator:BOOL=OFF
-DBUILD_opencv_objc_bindings_generator:BOOL=OFF
../opencv
ABI是arm64-v8a，ANDROID_PLATFORM是26，NDK是v21e。编译是在一个基于ubuntu groovy的docker镜像中完成的。
cmake的输出为
-- General configuration for OpenCV 4.5.1 =====================================
-- Version control: 4.5.1
--
-- Extra modules:
-- Location (extra): /root/opencv_contrib/modules
-- Version control (extra): 4.5.1
--
-- Platform:
-- Timestamp: 2021-03-22T20:16:30Z
-- Host: Linux 5.4.0-66-generic x86_64
-- Target: Android 1 aarch64
-- CMake: 3.16.3
-- CMake generator: Ninja
-- CMake build tool: /usr/bin/ninja
-- Configuration: Release
--
-- CPU/HW features:
-- Baseline: NEON FP16
--
-- C/C++:
-- Built as dynamic libs?: NO
-- C++ standard: 11
-- C++ Compiler: /opt/android-ndk-r21e/toolchains/llvm/prebuilt/linux-x86_64/bin/clang++ (ver 9.0)
-- C++ flags (Release): -g -DANDROID -fdata-sections -ffunction-sections -funwind-tables -fstack-protector-strong -no-canonical-prefixes -D_FORTIFY_SOURCE=2 -Wformat -Werror=format-security -fsigned-char -W -Wall -Werror=return-type -Werror=non-virtual-dtor -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes -Wundef -Winit-self -Wpointer-arith -Wshadow -Wsign-promo -Wuninitialized -Winconsistent-missing-override -Wno-delete-non-virtual-dtor -Wno-unnamed-type-template-args -Wno-comment -fdiagnostics-show-option -Qunused-arguments -fvisibility=hidden -fvisibility-inlines-hidden -O2 -DNDEBUG -Os -DNDEBUG
-- C++ flags (Debug): -g -DANDROID -fdata-sections -ffunction-sections -funwind-tables -fstack-protector-strong -no-canonical-prefixes -D_FORTIFY_SOURCE=2 -Wformat -Werror=format-security -fsigned-char -W -Wall -Werror=return-type -Werror=non-virtual-dtor -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes -Wundef -Winit-self -Wpointer-arith -Wshadow -Wsign-promo -Wuninitialized -Winconsistent-missing-override -Wno-delete-non-virtual-dtor -Wno-unnamed-type-template-args -Wno-comment -fdiagnostics-show-option -Qunused-arguments -fvisibility=hidden -fvisibility-inlines-hidden -O0 -fno-limit-debug-info -DDEBUG -D_DEBUG
-- C Compiler: /opt/android-ndk-r21e/toolchains/llvm/prebuilt/linux-x86_64/bin/clang
-- C flags (Release): -g -DANDROID -fdata-sections -ffunction-sections -funwind-tables -fstack-protector-strong -no-canonical-prefixes -D_FORTIFY_SOURCE=2 -Wformat -Werror=format-security -fsigned-char -W -Wall -Werror=return-type -Werror=non-virtual-dtor -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes -Wundef -Winit-self -Wpointer-arith -Wshadow -Wsign-promo -Wuninitialized -Winconsistent-missing-override -Wno-delete-non-virtual-dtor -Wno-unnamed-type-template-args -Wno-comment -fdiagnostics-show-option -Qunused-arguments -fvisibility=hidden -fvisibility-inlines-hidden -O2 -DNDEBUG -Os -DNDEBUG
-- C flags (Debug): -g -DANDROID -fdata-sections -ffunction-sections -funwind-tables -fstack-protector-strong -no-canonical-prefixes -D_FORTIFY_SOURCE=2 -Wformat -Werror=format-security -fsigned-char -W -Wall -Werror=return-type -Werror=non-virtual-dtor -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes -Wundef -Winit-self -Wpointer-arith -Wshadow -Wsign-promo -Wuninitialized -Winconsistent-missing-override -Wno-delete-non-virtual-dtor -Wno-unnamed-type-template-args -Wno-comment -fdiagnostics-show-option -Qunused-arguments -fvisibility=hidden -fvisibility-inlines-hidden -O0 -fno-limit-debug-info -DDEBUG -D_DEBUG
-- Linker flags (Release): -Wl,--exclude-libs,libgcc.a -Wl,--exclude-libs,libgcc_real.a -Wl,--exclude-libs,libatomic.a -static-libstdc++ -Wl,--build-id -Wl,--fatal-warnings -Wl,--no-undefined -Qunused-arguments -Wl,--as-needed
-- Linker flags (Debug): -Wl,--exclude-libs,libgcc.a -Wl,--exclude-libs,libgcc_real.a -Wl,--exclude-libs,libatomic.a -static-libstdc++ -Wl,--build-id -Wl,--fatal-warnings -Wl,--no-undefined -Qunused-arguments -Wl,--as-needed
-- ccache: NO
-- Precompiled headers: NO
-- Extra dependencies: ade /opt/android-ndk-r21e/toolchains/llvm/prebuilt/linux-x86_64/sysroot/usr/lib/aarch64-linux-android/libz.a dl m log
-- 3rdparty dependencies: libcpufeatures ittnotify libprotobuf libjpeg-turbo libwebp libpng libtiff libopenjp2 IlmImf quirc tegra_hal
--
-- OpenCV modules:
-- To be built: aruco bgsegm bioinspired calib3d core datasets dnn dnn_objdetect dnn_superres dpm face features2d flann fuzzy gapi hfs img_hash imgcodecs imgproc intensity_transform java line_descriptor mcc ml objdetect optflow phase_unwrapping photo plot quality rapid reg rgbd saliency shape stereo stitching structured_light superres surface_matching text tracking video videoio videostab xfeatures2d ximgproc xobjdetect xphoto
-- Disabled: highgui js_bindings_generator objc_bindings_generator world
-- Disabled by dependency: ccalib
-- Unavailable: alphamat cnn_3dobj cudaarithm cudabgsegm cudacodec cudafeatures2d cudafilters cudaimgproc cudalegacy cudaobjdetect cudaoptflow cudastereo cudawarping cudev cvv freetype hdf julia matlab ovis python2 python3 sfm ts viz
-- Applications: -
-- Documentation: NO
-- Non-free algorithms: NO
--
-- Android NDK: /opt/android-ndk-r21e (ver 21.4.7075529)
-- Android ABI: arm64-v8a
-- NDK toolchain: aarch64-linux-android-clang
-- STL type: c++_static
-- Native API level: 26
-- Android SDK: /opt/android_sdk (tools: 26.1.1 build tools: 30.0.3)
--
-- GUI:
--
-- Media I/O:
-- ZLib: /opt/android-ndk-r21e/toolchains/llvm/prebuilt/linux-x86_64/sysroot/usr/lib/aarch64-linux-android/libz.a (ver 1.2.7)
-- JPEG: build-libjpeg-turbo (ver 2.0.6-62)
-- WEBP: build (ver encoder: 0x020f)
-- PNG: build (ver 1.6.37)
-- TIFF: build (ver 42 - 4.0.10)
-- JPEG 2000: build (ver 2.3.1)
-- OpenEXR: build (ver 2.3.0)
-- HDR: YES
-- SUNRASTER: YES
-- PXM: YES
-- PFM: YES
--
-- Video I/O:
--
-- Parallel framework: pthreads
--
-- Trace: YES (with Intel ITT)
--
-- Other third-party libraries:
-- Custom HAL: YES (carotene (ver 0.0.1))
-- Protobuf: build (3.5.1)
--
-- Python (for build): /usr/bin/python3
--
-- Java: export all functions
-- ant: NO
-- Java wrappers: YES
-- Java tests: NO
--
-- Install to: /root/build/install
-- -----------------------------------------------------------------
你知道为什么我的图书馆这么大吗？
[1]https://sourceforge.net/projects/opencvlibrary/files/4.5.1/
我发现了罪魁祸首：
-DINSTALL_CREATE_DISTRIB=ON
文献中如此巧妙地表述"；调整多种内容以生成Windows和Android发行版"将库大小从45MB减少到5MB。
不带INSTALL_CREATE_DISTRIB=ON:
root@42ce12b54820:~/build# ll -h install/sdk/native/staticlibs/arm64-v8a/libopencv_core.a
-rw-r--r-- 1 root root 48M Mar 23 09:04 install/sdk/native/staticlibs/arm64-v8a/libopencv_core.a
INSTALL_CREATE_DISTRIB=ON时：
root@42ce12b54820:~/build# ll -h install/sdk/native/staticlibs/arm64-v8a/libopencv_core.a
-rw-r--r-- 1 root root 5.6M Mar 23 09:12 install/sdk/native/staticlibs/arm64-v8a/libopencv_core.a
：轻微_微笑：