OpenCv4.0.1ForAndroid环境搭建CMake-优快云博客

本文详细介绍如何在Android项目中整合OpenCV，通过NDK和CMake配置环境，实现高效的图像处理功能。从环境搭建、库集成到具体代码实现，包括通过JNI调用OpenCV库进行灰度转换的示例。

准备工作

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 创建一个Project 记得勾选supportC++ 3 下载 openCv https://opencv.org/releases.html 当前最新 4.0.1

开始配置

注意：考虑到java处理图片的效率本人使用的并非是OpenCv提供的JavaSDK而是通过jni调用其提供的 libopencv_java4.so动态库 1 在main目录下创建jniLibs目录并把解压后的opencv的 sdk/native/libs/ 下的所有内容copy到jniLibs下：

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

set(OPENCV_PATH #OpenCV的解压后的路径# ) 
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
        )
复制代码

3 设置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)
复制代码

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++) {
        //计算公式：Y(亮度) = 0.299*R + 0.587*G + 0.114*B
        //对于一个int四字节，其彩色值存储方式为：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;
}
复制代码

5 调用在activity中调用：

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")
        }
    }
}
复制代码

结果预览：