準(zhǔn)備工作

1 NDK(不需要指定版本目前最新19) CMake 正常使用AS的SDKManager添加即可
2 創(chuàng)建一個(gè)Project 記得勾選supportC++
3 下載 openCv https://opencv.org/releases.html 當(dāng)前最新 4.0.1

開(kāi)始配置

注意：考慮到j(luò)ava處理圖片的效率本人使用的并非是OpenCv提供的JavaSDK而是通過(guò)jni調(diào)用其提供的 libopencv_java4.so動(dòng)態(tài)庫(kù)
1 在main目錄下創(chuàng)建jniLibs目錄并把解壓后的opencv的 sdk/native/libs/ 下的所有內(nèi)容copy到j(luò)niLibs下：

image.png

2 修改CMakeLists.txt 文件：在 cmake_minimum_required(VERSION 3.4.1)下添加

set(OPENCV_PATH #OpenCV的解壓后的路徑# ) 
set(CMAKE_VERBOSE_MAKEFILE on)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=gnu++11")
include_directories(${OPENCV_PATH}/sdk/native/jni/include)
add_library(lib_opencv STATIC IMPORTED)
set_target_properties(lib_opencv
        PROPERTIES
        IMPORTED_LOCATION ${PROJECT_SOURCE_DIR}/src/main/jniLibs/${ANDROID_ABI}/libopencv_java4.so
        )

3 設(shè)置target_link_libraries:

target_link_libraries( # Specifies the target library.
        native-lib

        # Links the target library to the log library
        # included in the NDK.
        ${log-lib}
        android
        -ljnigraphics
        lib_opencv)

4 修改native-lib：

#include <jni.h>
#include <string>
#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <opencv2/opencv.hpp>

using namespace cv;
using namespace std;

extern "C" JNIEXPORT jintArray JNICALL
Java_com_demo_androidopencvdemo_MainActivity_gray(JNIEnv *env, jobject instance, jintArray buf, jint w,
                                                  jint h) {
    jint *cbuf = env->GetIntArrayElements(buf, JNI_FALSE);
    if (cbuf == NULL) {
        return 0;
    }

    Mat imgData(h, w, CV_8UC4, (unsigned char *) cbuf);

    uchar *ptr = imgData.ptr(0);
    for (int i = 0; i < w * h; i++) {
        //計(jì)算公式：Y(亮度) = 0.299*R + 0.587*G + 0.114*B
        //對(duì)于一個(gè)int四字節(jié)，其彩色值存儲(chǔ)方式為：BGRA
        int grayScale = (int) (ptr[4 * i + 2] * 0.299 + ptr[4 * i + 1] * 0.587 + ptr[4 * i + 0] * 0.114);
        ptr[4 * i + 1] = grayScale;
        ptr[4 * i + 2] = grayScale;
        ptr[4 * i + 0] = grayScale;
    }

    int size = w * h;
    jintArray result = env->NewIntArray(size);
    env->SetIntArrayRegion(result, 0, size, cbuf);
    env->ReleaseIntArrayElements(buf, cbuf, 0);
    return result;
}

5 調(diào)用在activity中調(diào)用：

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        iv_source.setImageResource(R.mipmap.img_head)
        val bitmapDrawable = resources.getDrawable(R.mipmap.img_head, null) as BitmapDrawable
        val bitmap = bitmapDrawable.bitmap
        val width = bitmap.width
        val height = bitmap.height
        val pix = IntArray(width * height)
        bitmap.getPixels(pix, 0, width, 0, 0, width, height)
        val resultPixels = gray(pix, width, height)
        val result = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888)
        result.setPixels(resultPixels,0,width,0,0,width,height)
        iv_target.setImageBitmap(result)


    }

    external fun gray(buf: IntArray, w: Int, h: Int): IntArray

    companion object {

        // Used to load the 'native-lib' library on application startup.
        init {
            System.loadLibrary("native-lib")
        }
    }
}

結(jié)果預(yù)覽：

image.png