Android的OpenCV ndk编程

由于OpenCV开源图像处理代码简单，因此常用于各种平台中。采用NDK编程可以方便的使用OpenCV资源。

使用OpenCV的NDK编程主要包括两部分：

1、添加OpenCV库，用ndk-build编译，Linux系统下

1.1 Android.mk

LOCAL_PATH:=$(call my-dir)

include $(CLEAR_VARS)

OpenCV_INSTALL_MODULES := on

OpenCV_CAMERA_MODULES := off

OPENCV_LIB_TYPE :=STATIC

include /home/zzw/AndroidStudioProjects/opencv_face/OpenCV-android-sdk/sdk/native/jni/OpenCV.mk //这里面包括OpenCV的配置

#LOCAL_SRC_FILES := squeezencnn_jni.cpp

LOCAL_MODULE    := JNIpart

LOCAL_SRC_FILES := OpenCVNDK.cpp

LOCAL_LDLIBS    += -llog -lGLESv2 -lEGL -ljnigraphics

include $(BUILD_SHARED_LIBRARY)

1.2 Application.mk 切记NDK的版本不能太高了

 # APP_STL := stlport_static

APP_STL := gnustl_static

# APP_ABI := armeabi armeabi-v7a

APP_CPPFLAGS := -std=c++11 -frtti -fexceptions

APP_ABI := armeabi-v7a

APP_PLATFORM := android-14

#NDK_TOOLCHAIN_VERSION := 10

2、OpenCVNDK.cpp 文件编写

JNIEXPORT jobject JNICALL Java_com_example_root_cameralopencv_MainActivity_FaceDetection

(JNIEnv* env, jobject thiz, jobject bitmap)

{

    AndroidBitmapInfo info;

    AndroidBitmap_getInfo(env, bitmap, &info);

    int width = info.width;

    int height = info.height;

    unsigned char* indata;

    AndroidBitmap_lockPixels(env, bitmap, (void**)&indata);

    //image copy bimap的数据格式为ARGB，因此需要后续的转化和采用CV_8UC4格式

    cv::Mat imgData(height, width, CV_8UC4, indata);

    AndroidBitmap_unlockPixels(env, bitmap);

   //返回Bimap格式，Mat 转bimap.

    jobject bitmaptemp;

    jclass bitmapCls = env->GetObjectClass(bitmap);

    jmethodID createBitmapFunction = env->GetStaticMethodID(bitmapCls, "createBitmap", "(IILandroid/graphics/Bitmap$Config;)Landroid/graphics/Bitmap;");

    jstring configName = env->NewStringUTF("ARGB_8888");

    jclass bitmapConfigClass = env->FindClass("android/graphics/Bitmap$Config");

    jmethodID valueOfBitmapConfigFunction = env->GetStaticMethodID(bitmapConfigClass, "valueOf", "(Ljava/lang/String;)Landroid/graphics/Bitmap$Config;");

    jobject bitmapConfig = env->CallStaticObjectMethod(bitmapConfigClass, valueOfBitmapConfigFunction, configName);

    jobject newBitmap = env->CallStaticObjectMethod(bitmapCls, createBitmapFunction, info.width, info.height, bitmapConfig);

    unsigned char* newBitmapPixels;

    AndroidBitmap_lockPixels(env, newBitmap, (void**)&newBitmapPixels);

    for(int i = 0; i < info.width*info.height*4; i+=4){

                //unsigned char g = imgData.data[i];

                newBitmapPixels[i] = imgData.data[i];

                newBitmapPixels[i+1] = imgData.data[i+1];

                newBitmapPixels[i+2] = imgData.data[i+2];

                newBitmapPixels[i+3] = imgData.data[i+3];

    }

      AndroidBitmap_unlockPixels(env, newBitmap);

      return newBitmap;

}