利用OPENCV为android相机开发图像处理库

android调用opencv的方法有三种，利于OPENCVSDK manager调用，这种方法最简单，不过需要安装客户端，相对来说，很多适合都是不适用的。一种是使用OPENCV提供的JAVA库加SO库调用，这种方法相当来说，省掉了多安装一个APP的负责，更有利于软件推广。最后一种是利于JNI调用OPENV的C／C+语言库完成相关功能模块开发，并给JAVA层提供相应的调用接口，这种方式个人感觉效率最高。

使用OPENCV开发相机，一般是借且三种方式，一种是camera的previcewcallback接口提供的预览回调，一种是使用camera2的 ImageReader接口，还有一种使用OPENGL的shader开发相应接口，一旦加了特殊处理，都会产生丢帧。

从相机获取的数据都是YUV格式的BYTE数组，在opencv中先把其转为RGB数组，再对其做畸变，美颜，人脸查找，应用分割或者其他滤镜等技术。

先创建JAVA调用，这里写两个函数，一个YUV转为灰度，一个YUV转为RGBA，文件名字ImageProc，包名myopencv

package myopencv;public class ImageProc {static {System.loadLibrary("ImageProc");}public static native boolean convertGray(int width, int height, byte[] NV21FrameData, int[] pixels);public static native boolean convertRGBA(int width, int height,  byte[] yuv, int[] pixels);}

调用JAVAH生成头文件，头文件不是必需的，如果熟了，可以直接CPP文件

javah -classpath F:\luna5\mycam\bin\classes\ -jni myopencv.ImageProc

/* DO NOT EDIT THIS FILE - it is machine generated */#include <jni.h>/* Header for class myopencv_ImageProc */#ifndef _Included_myopencv_ImageProc#define _Included_myopencv_ImageProc#ifdef __cplusplusextern "C" {#endif/* * Class:     myopencv_ImageProc * Method:    convertGray * Signature: (II[B[I)Z */JNIEXPORT jboolean JNICALL Java_myopencv_ImageProc_convertGray  (JNIEnv *, jclass, jint, jint, jbyteArray, jintArray);/* * Class:     myopencv_ImageProc * Method:    convertRGBA * Signature: (II[B[I)Z */JNIEXPORT jboolean JNICALL Java_myopencv_ImageProc_convertRGBA  (JNIEnv *, jclass, jint, jint, jbyteArray, jintArray);#ifdef __cplusplus}#endif#endif

使用opencv编写相应的功能代码

#include <stdio.h>#include <jni.h>#include<Android/log.h>#include <opencv2/core/core.hpp>#include <opencv2/highgui/highgui.hpp>#include <opencv2/imgproc/imgproc.hpp>using namespace std;using namespace cv;#define TAG    "Camera XXXXX" // 这个是自定义的LOG的标识#define LOGD(...)  __android_log_print(ANDROID_LOG_DEBUG,TAG,__VA_ARGS__) // 定义LOGD类型extern "C"{    jboolean Java_myopencv_ImageProc_convertGray(        JNIEnv* env, jobject thiz, jint width, jint height,        jbyteArray NV21FrameData, jintArray outPixels)    {        jbyte * pNV21FrameData = env->GetByteArrayElements(NV21FrameData, 0);        jint * poutPixels = env->GetIntArrayElements(outPixels, 0);                Mat mNV(height, width, CV_8UC1, (unsigned char*)pNV21FrameData);        Mat mBgra(height, width, CV_8UC4, (unsigned char*) poutPixels);        cvtColor(mNV, mBgra, CV_GRAY2RGBA);        env->ReleaseByteArrayElements(NV21FrameData, pNV21FrameData, 0);        env->ReleaseIntArrayElements(outPixels, poutPixels, 0);        return true;    }    jboolean Java_myopencv_ImageProc_convertRGBA(    JNIEnv *env, jobject thiz, jint width, jint height, jbyteArray yuv, jintArray outPixels)    {        jbyte * pBuf = (jbyte*)env->GetByteArrayElements(yuv, 0);        jint * poutPixels = env->GetIntArrayElements(outPixels, 0);        Mat image(height + height/2, width, CV_8UC1, (unsigned char *)pBuf);        Mat mBgra(height, width, CV_8UC4, (unsigned char*) poutPixels);        cvtColor(image, mBgra, CV_YUV420sp2RGBA);        LOGD("jiaXXX %X", poutPixels[0]);        env->ReleaseByteArrayElements(yuv, pBuf, 0);        env->ReleaseIntArrayElements(outPixels, poutPixels, 0);        return true;    }    jboolean Java_myopencv_ImageProc_convertBeauty(        JNIEnv *env, jobject thiz, jint width, jint height, jbyteArray yuv, jintArray outPixels)    {        return true;    }    jboolean Java_myopencv_ImageProc_convertBackBlur(        JNIEnv *env, jobject thiz, jint width, jint height, jbyteArray yuv, jintArray outPixels)    {        return true;    }}

编写MK文件，Application.mk,为了兼容性，参数使用 ALL，生成所有支持的CPU的库

APP_STL := gnustl_staticAPP_CPPFLAGS := -frtti -fexceptionsAPP_ABI := allAPP_PLATFORM := android-8

编写Android.mk文件

LOCAL_PATH := $(call my-dir)include $(CLEAR_VARS)OPENCV_LIB_TYPE:=STATICOPENCV_INSTALL_MODULES:=oninclude C:/Users/jiazhiguo/Downloads/opencv/sources/samples/android/sdk/native/jni/OpenCV.mkLOCAL_MODULE    := ImageProcLOCAL_SRC_FILES := ImageProc.cppLOCAL_LDLIBS +=  -llog -ldlinclude $(BUILD_SHARED_LIBRARY)

注意路径，由于是使用OPENCV开发，对OPENCV有依赖，编译时需要OPENCV路径，我的OPENCV的SDK路径在C盘，需要改成自己的

ndk-build生成相应libImageProc.so库在项目中使用.

ImageProc.convertRGBA(previewSizeWidth, previewSizeHeight, mData, pixels);