OpenCV Android SDK中提供的静态、动态库是不支持OpenCL加速的，如果在程序中调用OpenCL相关函数，编译时不会报错，但运行时logcat会输出如下信息，提示OpenCL函数不可用
08-11 11:43:07.140: E/cv::error()(18198): OpenCV Error: Unknown error code -6 (OpenCL function is not available: [clGetPlatformIDs]) in void* opencl_check_fn(int), file /hdd2/buildbot/slaves/slave_ardbeg1/50-SDK/opencv/modules/ocl/src/cl_runtime/cl_runtime.cpp, line 83 08-11 11:43:07.140: E/cv::error()(18198): OpenCV Error: Unknown error code -221 (OpenCL not available) in static cv::ocl::ContextImpl* cv::ocl::ContextImpl::getContext(), file /hdd2/buildbot/slaves/slave_ardbeg1/50-SDK/opencv/modules/ocl/src/cl_context.cpp, line 678
所以，如果想使用OpenCV for Android中的ocl模块，需要自己编译一套支持OpenCL的OpenCV库文件，同时还需要有一部具有OpenCL驱动的设备。下面详细讲述整个过程，整个的编译过程都是基于windows平台的，其他平台过程类似，只是编译时的命令会有所不同。
1.如何判断设备是否支持OpenCL
可以下载一款叫OpenCL-Z的软件。安装后，它可以检测当前设备的GPU是否支持OpenCL和是否具有OpenCL驱动。下面是豌豆荚上的下载地址：
http://www.wandoujia.com/apps/com.robertwgh.opencl_z_android
不过有的时候设备的GPU支持OpenCL但是没有安装正确的驱动，这个时候需要如下几个不住：
A.确定设备的GPU型号，这个可以通过google，baidu搞定。
B.通过https://www.khronos.org/conformance/adopters/conformant-products/网站查询你的GPU型号是否支持OpenCL
C.如果支持，例如Adreno330，可以去对应的网站下载驱动更新。Adreno330的驱动下载网址：https://developer.qualcomm.com/software/adreno-gpu-sdk/tools，下载链接在Drivers这一项下面。
D.根据驱动中的说明文档，刷机->更新驱动。（其实这个过程挺麻烦，不过我的确让4.4系统的nexus5支持OpenCL了）
2.编译带OpenCL模块的OpenCV for Android
（1）首先需要从OpenCV官网下载源码，我是基于2.4.11版本的源码编译的（3.x版本工程整体结构变化太大，而且单独的ocl模块被合入其他模块了，我还没搞明白怎么用）。
这个网址可以下载到2.4.11版本的源码：https://github.com/Itseez/opencv/releases
（2）接下来配置需要的工具，主要有两个：cmake，Android ndk。下载&安装，在环境变量中配置好cmake的bin目录，并将ndk的根目录添加为ANDROID_NDK值。
（3）在opencv_pathmodulesoclsrccl_runtimecl_runtime.cpp文件中，做如下修改：
第48行，#if defined(__linux__) 改为 #if defined(__linux__)&&!defined(__ANDROID__)
第70行后，添加如下代码：
#if defined(__ANDROID__) #include <dlfcn.h> #include <sys/stat.h> #if defined(__ARM_ARCH_8A__) || defined(_X64_) static const char *default_so_paths[] = { "/system/lib64/libOpenCL.so", "/system/vendor/lib64/libOpenCL.so", "/system/vendor/lib64/egl/libGLES_mali.so" }; #else static const char *default_so_paths[] = { "/system/lib/libOpenCL.so", "/system/vendor/lib/libOpenCL.so", "/system/vendor/lib/egl/libGLES_mali.so" }; #endif static int access_file(const char *filename) { struct stat buffer; return (stat(filename, &buffer) == 0); } static void* GetProcAddress (const char* name) { static void* h = NULL; unsigned int i; if (!h) { const char* name; for(i=0; i<(sizeof(default_so_paths)/sizeof(char*)); i++) { if(access_file(default_so_paths[i])) { name = (char *)default_so_paths[i]; h = dlopen(name, RTLD_LAZY); if (h) break; } } if (!h) return NULL; } return dlsym(h, name); } #define CV_CL_GET_PROC_ADDRESS(name) GetProcAddress(name) #endif
（4）编译opencv。打开cmd，将当前目录切换到opencv_pathplatforms下面，执行如下命令：
1 mkdir build_opencl 2 cd build_opencl 3 cmake -G "MinGW Makefiles" -DCMAKE_BUILD_WITH_INSTALL_RPATH=ON -DWITH_EIGEN=off -DCMAKE_TOOLCHAIN_FILE=..androidandroid.toolchain.cmake -DCMAKE_MAKE_PROGRAM="%ANDROID_NDK%prebuiltwindows-x86_64inmake.exe" -DANDROID_ABI=armeabi ....
其中，ANDROID_NDK是在环境变量中设置好的变量值，为android ndk的根目录，DANDROID_ABI可以根据需要选择。执行完毕后，执行如下命令即可：
cmake --build .
注意build后面的那个“.”不能少。
（5）编译完成后，把uild_opencllibarmeabi下面的库覆盖到opencv android sdk中的sdk ativelibs目录下对应的文件夹。
（6）clean原有的工程，然后build project。在设备上运行，一切OK。
这里是测试工程的源码，需要用自己图片path替换代码中的path，然后app会在同一目录下生成一幅灰度图。例如：输入图像为设备根目录下a.jpg，运行后同一目录下会生成agray.jpg灰度图片。
更新：
编译带有OpenCL模块的OpenCV3.0.0 for android
1.根目录下的CMakeLists.txt中，设置WITH_OPENCL为ON
2.modulescoresrcopencl untimeopencl_core.cpp文件中，按照OpenCV2.4.11的方法修改并添加代码：
/*M/////////////////////////////////////////////////////////////////////////////////////// // // IMPORTANT: READ BEFORE DOWNLOADING, COPYING, INSTALLING OR USING. // // By downloading, copying, installing or using the software you agree to this license. // If you do not agree to this license, do not download, install, // copy or use the software. // // // License Agreement // For Open Source Computer Vision Library // // Copyright (C) 2010-2013, Advanced Micro Devices, Inc., all rights reserved. // Third party copyrights are property of their respective owners. // // Redistribution and use in source and binary forms, with or without modification, // are permitted provided that the following conditions are met: // // * Redistribution's of source code must retain the above copyright notice, // this list of conditions and the following disclaimer. // // * Redistribution's in binary form must reproduce the above copyright notice, // this list of conditions and the following disclaimer in the documentation // and/or other materials provided with the distribution. // // * The name of the copyright holders may not be used to endorse or promote products // derived from this software without specific prior written permission. // // This software is provided by the copyright holders and contributors "as is" and // any express or implied warranties, including, but not limited to, the implied // warranties of merchantability and fitness for a particular purpose are disclaimed. // In no event shall the OpenCV Foundation or contributors be liable for any direct, // indirect, incidental, special, exemplary, or consequential damages // (including, but not limited to, procurement of substitute goods or services; // loss of use, data, or profits; or business interruption) however caused // and on any theory of liability, whether in contract, strict liability, // or tort (including negligence or otherwise) arising in any way out of // the use of this software, even if advised of the possibility of such damage. // //M*/ #include "../../precomp.hpp" #if defined(HAVE_OPENCL) && !defined(HAVE_OPENCL_STATIC) #include "opencv2/core.hpp" // CV_Error #include "opencv2/core/opencl/runtime/opencl_core.hpp" #define OPENCL_FUNC_TO_CHECK_1_1 "clEnqueueReadBufferRect" #define ERROR_MSG_CANT_LOAD "Failed to load OpenCL runtime " #define ERROR_MSG_INVALID_VERSION "Failed to load OpenCL runtime (expected version 1.1+) " #if defined(__APPLE__) #include <dlfcn.h> static void* AppleCLGetProcAddress(const char* name) { static bool initialized = false; static void* handle = NULL; if (!handle) { if(!initialized) { initialized = true; const char* path = "/System/Library/Frameworks/OpenCL.framework/Versions/Current/OpenCL"; const char* envPath = getenv("OPENCV_OPENCL_RUNTIME"); if (envPath) path = envPath; handle = dlopen(oclpath, RTLD_LAZY | RTLD_GLOBAL); if (handle == NULL) { if (envPath) fprintf(stderr, ERROR_MSG_CANT_LOAD); } else if (dlsym(handle, OPENCL_FUNC_TO_CHECK_1_1) == NULL) { fprintf(stderr, ERROR_MSG_INVALID_VERSION); handle = NULL; } } if (!handle) return NULL; } return dlsym(handle, name); } #define CV_CL_GET_PROC_ADDRESS(name) AppleCLGetProcAddress(name) #endif // __APPLE__ #if defined(_WIN32) #include <windows.h> static void* WinGetProcAddress(const char* name) { static bool initialized = false; static HMODULE handle = NULL; if (!handle) { if(!initialized) { initialized = true; handle = GetModuleHandleA("OpenCL.dll"); if (!handle) { const char* path = "OpenCL.dll"; const char* envPath = getenv("OPENCV_OPENCL_RUNTIME"); if (envPath) path = envPath; handle = LoadLibraryA(path); if (!handle) { if (envPath) fprintf(stderr, ERROR_MSG_CANT_LOAD); } else if (GetProcAddress(handle, OPENCL_FUNC_TO_CHECK_1_1) == NULL) { fprintf(stderr, ERROR_MSG_INVALID_VERSION); handle = NULL; } } } if (!handle) return NULL; } return (void*)GetProcAddress(handle, name); } #define CV_CL_GET_PROC_ADDRESS(name) WinGetProcAddress(name) #endif // _WIN32 #if defined(__linux__)&&!defined(__ANDROID__) #include <dlfcn.h> #include <stdio.h> static void* GetProcAddress(const char* name) { static bool initialized = false; static void* handle = NULL; if (!handle) { if(!initialized) { initialized = true; const char* path = "libOpenCL.so"; const char* envPath = getenv("OPENCV_OPENCL_RUNTIME"); if (envPath) path = envPath; handle = dlopen(path, RTLD_LAZY | RTLD_GLOBAL); if (handle == NULL) { if (envPath) fprintf(stderr, ERROR_MSG_CANT_LOAD); } else if (dlsym(handle, OPENCL_FUNC_TO_CHECK_1_1) == NULL) { fprintf(stderr, ERROR_MSG_INVALID_VERSION); handle = NULL; } } if (!handle) return NULL; } return dlsym(handle, name); } #define CV_CL_GET_PROC_ADDRESS(name) GetProcAddress(name) #endif //linux #if defined(__ANDROID__) #include <dlfcn.h> #include <sys/stat.h> #if defined(__ARM_ARCH_8A__) || defined(_X64_) static const char *default_so_paths[] = { "/system/lib64/libOpenCL.so", "/system/vendor/lib64/libOpenCL.so", "/system/vendor/lib64/egl/libGLES_mali.so" }; #else static const char *default_so_paths[] = { "/system/lib/libOpenCL.so", "/system/vendor/lib/libOpenCL.so", "/system/vendor/lib/egl/libGLES_mali.so" }; #endif static int access_file(const char *filename) { struct stat buffer; return (stat(filename, &buffer) == 0); } static void* GetProcAddress (const char* name) { static void* h = NULL; unsigned int i; if (!h) { const char* name; for(i=0; i<(sizeof(default_so_paths)/sizeof(char*)); i++) { if(access_file(default_so_paths[i])) { name = (char *)default_so_paths[i]; h = dlopen(name, RTLD_LAZY); if (h) break; } } if (!h) return NULL; } return dlsym(h, name); } #define CV_CL_GET_PROC_ADDRESS(name) GetProcAddress(name) #endif //android #ifndef CV_CL_GET_PROC_ADDRESS #ifdef __GNUC__ #warning("OPENCV: OpenCL dynamic library loader: check configuration") #else #pragma message("WARNING: OPENCV: OpenCL dynamic library loader: check configuration") #endif #define CV_CL_GET_PROC_ADDRESS(name) NULL #endif static void* opencl_check_fn(int ID); #include "runtime_common.hpp" #include "autogenerated/opencl_core_impl.hpp" // // BEGIN OF CUSTOM FUNCTIONS // #define CUSTOM_FUNCTION_ID 1000 #ifdef HAVE_OPENCL_SVM #include "opencv2/core/opencl/runtime/opencl_svm_20.hpp" #define SVM_FUNCTION_ID_START CUSTOM_FUNCTION_ID #define SVM_FUNCTION_ID_END CUSTOM_FUNCTION_ID + 100 enum OPENCL_FN_SVM_ID { OPENCL_FN_clSVMAlloc = SVM_FUNCTION_ID_START, OPENCL_FN_clSVMFree, OPENCL_FN_clSetKernelArgSVMPointer, OPENCL_FN_clSetKernelExecInfo, OPENCL_FN_clEnqueueSVMFree, OPENCL_FN_clEnqueueSVMMemcpy, OPENCL_FN_clEnqueueSVMMemFill, OPENCL_FN_clEnqueueSVMMap, OPENCL_FN_clEnqueueSVMUnmap, }; void* (CL_API_CALL *clSVMAlloc)(cl_context context, cl_svm_mem_flags flags, size_t size, unsigned int alignment) = opencl_fn4<OPENCL_FN_clSVMAlloc, void*, cl_context, cl_svm_mem_flags, size_t, unsigned int>::switch_fn; static const struct DynamicFnEntry _clSVMAlloc_definition = { "clSVMAlloc", (void**)&clSVMAlloc}; void (CL_API_CALL *clSVMFree)(cl_context context, void* svm_pointer) = opencl_fn2<OPENCL_FN_clSVMFree, void, cl_context, void*>::switch_fn; static const struct DynamicFnEntry _clSVMFree_definition = { "clSVMFree", (void**)&clSVMFree}; cl_int (CL_API_CALL *clSetKernelArgSVMPointer)(cl_kernel kernel, cl_uint arg_index, const void* arg_value) = opencl_fn3<OPENCL_FN_clSetKernelArgSVMPointer, cl_int, cl_kernel, cl_uint, const void*>::switch_fn; static const struct DynamicFnEntry _clSetKernelArgSVMPointer_definition = { "clSetKernelArgSVMPointer", (void**)&clSetKernelArgSVMPointer}; //void* (CL_API_CALL *clSetKernelExecInfo)(cl_kernel kernel, cl_kernel_exec_info param_name, size_t param_value_size, const void* param_value) = // opencl_fn4<OPENCL_FN_clSetKernelExecInfo, void*, cl_kernel, cl_kernel_exec_info, size_t, const void*>::switch_fn; //static const struct DynamicFnEntry _clSetKernelExecInfo_definition = { "clSetKernelExecInfo", (void**)&clSetKernelExecInfo}; //cl_int (CL_API_CALL *clEnqueueSVMFree)(...) = // opencl_fn8<OPENCL_FN_clEnqueueSVMFree, cl_int, ...>::switch_fn; //static const struct DynamicFnEntry _clEnqueueSVMFree_definition = { "clEnqueueSVMFree", (void**)&clEnqueueSVMFree}; cl_int (CL_API_CALL *clEnqueueSVMMemcpy)(cl_command_queue command_queue, cl_bool blocking_copy, void* dst_ptr, const void* src_ptr, size_t size, cl_uint num_events_in_wait_list, const cl_event* event_wait_list, cl_event* event) = opencl_fn8<OPENCL_FN_clEnqueueSVMMemcpy, cl_int, cl_command_queue, cl_bool, void*, const void*, size_t, cl_uint, const cl_event*, cl_event*>::switch_fn; static const struct DynamicFnEntry _clEnqueueSVMMemcpy_definition = { "clEnqueueSVMMemcpy", (void**)&clEnqueueSVMMemcpy}; cl_int (CL_API_CALL *clEnqueueSVMMemFill)(cl_command_queue command_queue, void* svm_ptr, const void* pattern, size_t pattern_size, size_t size, cl_uint num_events_in_wait_list, const cl_event* event_wait_list, cl_event* event) = opencl_fn8<OPENCL_FN_clEnqueueSVMMemFill, cl_int, cl_command_queue, void*, const void*, size_t, size_t, cl_uint, const cl_event*, cl_event*>::switch_fn; static const struct DynamicFnEntry _clEnqueueSVMMemFill_definition = { "clEnqueueSVMMemFill", (void**)&clEnqueueSVMMemFill}; cl_int (CL_API_CALL *clEnqueueSVMMap)(cl_command_queue command_queue, cl_bool blocking_map, cl_map_flags map_flags, void* svm_ptr, size_t size, cl_uint num_events_in_wait_list, const cl_event* event_wait_list, cl_event* event) = opencl_fn8<OPENCL_FN_clEnqueueSVMMap, cl_int, cl_command_queue, cl_bool, cl_map_flags, void*, size_t, cl_uint, const cl_event*, cl_event*>::switch_fn; static const struct DynamicFnEntry _clEnqueueSVMMap_definition = { "clEnqueueSVMMap", (void**)&clEnqueueSVMMap}; cl_int (CL_API_CALL *clEnqueueSVMUnmap)(cl_command_queue command_queue, void* svm_ptr, cl_uint num_events_in_wait_list, const cl_event* event_wait_list, cl_event* event) = opencl_fn5<OPENCL_FN_clEnqueueSVMUnmap, cl_int, cl_command_queue, void*, cl_uint, const cl_event*, cl_event*>::switch_fn; static const struct DynamicFnEntry _clEnqueueSVMUnmap_definition = { "clEnqueueSVMUnmap", (void**)&clEnqueueSVMUnmap}; static const struct DynamicFnEntry* opencl_svm_fn_list[] = { &_clSVMAlloc_definition, &_clSVMFree_definition, &_clSetKernelArgSVMPointer_definition, NULL/*&_clSetKernelExecInfo_definition*/, NULL/*&_clEnqueueSVMFree_definition*/, &_clEnqueueSVMMemcpy_definition, &_clEnqueueSVMMemFill_definition, &_clEnqueueSVMMap_definition, &_clEnqueueSVMUnmap_definition, }; #endif // HAVE_OPENCL_SVM // // END OF CUSTOM FUNCTIONS HERE // static void* opencl_check_fn(int ID) { const struct DynamicFnEntry* e = NULL; if (ID < CUSTOM_FUNCTION_ID) { assert(ID >= 0 && ID < (int)(sizeof(opencl_fn_list)/sizeof(opencl_fn_list[0]))); e = opencl_fn_list[ID]; } #ifdef HAVE_OPENCL_SVM else if (ID >= SVM_FUNCTION_ID_START && ID < SVM_FUNCTION_ID_END) { ID = ID - SVM_FUNCTION_ID_START; assert(ID >= 0 && ID < (int)(sizeof(opencl_svm_fn_list)/sizeof(opencl_svm_fn_list[0]))); e = opencl_svm_fn_list[ID]; } #endif else { CV_ErrorNoReturn(cv::Error::StsBadArg, "Invalid function ID"); } void* func = CV_CL_GET_PROC_ADDRESS(e->fnName); if (!func) { throw cv::Exception(cv::Error::OpenCLApiCallError, cv::format("OpenCL function is not available: [%s]", e->fnName), CV_Func, __FILE__, __LINE__); } *(e->ppFn) = func; return func; } #endif
3.和2.4.11一样，创建文件夹，然后顺序执行如下编译命令：
cmake -G "MinGW Makefiles" -DCMAKE_BUILD_WITH_INSTALL_RPATH=ON -DWITH_OPENCL=ON -DWITH_EIGEN=off -DCMAKE_TOOLCHAIN_FILE=..androidandroid.toolchain.cmake -DCMAKE_MAKE_PROGRAM="%ANDROID_NDK%prebuiltwindows-x86_64inmake.exe" -DANDROID_ABI=armeabi .... cmake --build .