源码如下，实现把一个JPG保存成灰度图格式的BMP

1 //jpg2bmp.cpp
2 #include
3 #include
4 #include
5 #include
6
7 #ifndef P
8 #define P(format, …) do \
9 { \
10 printf("%s %s %d " format "\n", __FILE__, __FUNCTION__, __LINE__, ##__VA_ARGS__); \
11 fflush(stdout); \
12 } \
13 while (0);
14 #endif
15
16 int main(int argc, char* argv[]){
17 if (argc<3){ 18 printf("usage:%s \n", argv[0]);
19 return 0;
20 }
21 cv::Mat image = cv::imread(argv[1], cv::IMREAD_UNCHANGED);
22 cv::UMat u_img = image.getUMat(cv::ACCESS_READ);
23 if (image.empty()){
24 P("load pic %s fail", argv[1]);
25 return -1;
26 }
27 cv::UMat bmp;
28 cv::cvtColor(u_img, bmp, cv::COLOR_BGR2GRAY);
29 cv::imwrite(argv[2], bmp);
30 P("ok");
31 return 1;
32 }

编译命令行如下：

1 /Users/ahfu/code/android/android-ndk-r14b/toolchains/arm-linux-androideabi-4.9/prebuilt/darwin-x86_64/bin/arm-linux-androideabi-g++ \
2 -o jpg2bmp_1.o -c jpg2bmp_1.cpp -pie -fPIC \
3 -I"/Users/ahfu/code/android/OpenCV-android-sdk/sdk/native/jni/include" \
4 --sysroot=/Users/ahfu/code/android/android-ndk-r14b/platforms/android-22/arch-arm/ \
5 -I"/Users/ahfu/code/android/android-ndk-r14b/sources/cxx-stl/gnu-libstdc++/4.9/include" \
6 -I"/Users/ahfu/code/android/android-ndk-r14b/sources/cxx-stl/gnu-libstdc++/4.9/libs/armeabi-v7a/include/"

链接命令行如下：

1 /Users/ahfu/code/android/android-ndk-r14b/toolchains/arm-linux-androideabi-4.9/prebuilt/darwin-x86_64/bin/arm-linux-androideabi-g++ \
2 -o jpg2bmp_1 jpg2bmp_1.o -pie -fPIC \
3 --sysroot=/Users/ahfu/code/android/android-ndk-r14b/platforms/android-22/arch-arm/ \
4 -L"/Users/ahfu/code/android/OpenCV-android-sdk/sdk/native/staticlibs/armeabi-v7a" -lopencv_core -lopencv_imgcodecs -lopencv_imgproc -lm -lz -landroid -llog \
5 -L"/Users/ahfu/code/android/OpenCV-android-sdk/sdk/native/3rdparty/libs/armeabi-v7a/" -ltegra_hal -lcpufeatures -ltbb -llibpng -llibjpeg-turbo -llibtiff -llibjasper -llibwebp -lIlmImf -lopencv_core -lopencv_imgcodecs -lopencv_imgproc -ltegra_hal \
6 -L"/Users/ahfu/code/android/android-ndk-r14b/sources/cxx-stl/gnu-libstdc++/4.9/libs/armeabi-v7a" -lgnustl_static -lsupc++ \
7 -L"/Users/ahfu/code/android/android-ndk-r14b/platforms/android-22/arch-arm/usr/lib" -lstdc++

然后使用adb上传
adb root  #手机必要要root
adb push jpg2bmp 1.jpg /data/data/temp
adb shell
  cd /data/data/temp
  chmod +x jpg2bmp
  ./jpg2bmp 1.jpg 2.bmp

#执行成功

ndk版本是：android-ndk-r14b
opencv android sdk版本是：opencv-3.4.6-android-sdk.zip