使用AndroiStudio、Cmake 开发ndk 入门（下）利用c++处理Bitmap

野性酷女 2022-05-30 03:12 243阅读 0赞

接着上篇ndk入门环境搭建（http://blog.csdn.net/fengchengwu2012/article/details/79412501），今天来探讨一下使用android 平台下使用c++处理Bitmap

(1)在app/sarc/main下新建一个c++的源文件bitmap-lib.cpp

(2) 创建NdkUtils的java类，写相应处理图片的native方法，并执行javah生成ndk工具类映射到cpp的头文件

public class NdkUtils {
        static {
            System.loadLibrary("bitmap-lib");
        }
        public static  native int     convertBm(Bitmap  srtBm);
        public static native int[]    convertBmByPixels(int[] pixels, int w, int h);
    }

javah  -classpath  C:\\sdk\\platforms\\android-26\\android.jar;.   ndkdev.fcw.cn.bitamptool.NdkUtils

文件目录如下：

![70][]

（3）在bitmap-lib.cpp编写c++代码：

#include  <jni.h>
    #include  <string.h>
    #include <stdlib.h>
    #include <android/bitmap.h>
    #include <android/log.h>
    #include "ndkdev_fcw_cn_bitamptool_NdkUtils.h"
    #define LOG    "bitmap"
    #define LOGI(...)  __android_log_print(ANDROID_LOG_INFO,LOG,__VA_ARGS__)
    JNIEXPORT jintArray JNICALL Java_ndkdev_fcw_cn_bitamptool_NdkUtils_convertBmByPixels
            (JNIEnv *env, jclass job, jintArray jarr, jint w, jint h){
        jint *buffer=env->GetIntArrayElements(jarr, NULL);
        if (buffer!=NULL){
            int a=0xFF<<24;
            for(int i=h;i<h;i++){
                for(int j=0;j<w;j++){
                    int color = buffer[w * i + j];
                    int red = ((color & 0x00FF0000) >> 16);
                    int green = ((color & 0x0000FF00) >> 8);
                    int blue = color & 0x000000FF;
                    color = (red + green + blue) / 3;
                    color = a| (color << 16) | (color << 8) | color;
                    buffer[w * i + j] = color;
                }
            }
            jintArray res = env->NewIntArray(w * h);
            env->SetIntArrayRegion(res, 0,w * h, buffer);
    
            env->ReleaseIntArrayElements(jarr, buffer, 0);
            return res;
        } else{
            return 0;
        }
    }
    
    
    JNIEXPORT jint JNICALL Java_ndkdev_fcw_cn_bitamptool_NdkUtils_convertBm
            (JNIEnv *env, jclass  jc, jobject srcBm){
    }

（4）  写MainActivity的布局及java代码

public class MainActivity extends AppCompatActivity {
        private ImageView srcIv, desIv;
        private TextView mDoneTv;
        private MainActivity mActivity;
        private int w, h;
    
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
            mActivity = this;
            mDoneTv = findViewById(R.id.done_tv);
            srcIv = findViewById(R.id.src_iv);
            desIv = findViewById(R.id.des_iv);
            layoutIv(srcIv);
            layoutIv(desIv);
            mDoneTv.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    Bitmap tm = BitmapFactory.decodeResource(getResources(), R.drawable.lid).copy(Bitmap.Config.RGB_565, true);
                    Bitmap.createBitmap(tm, 0, 0, w, h);
                    Bitmap bitmap = getBitmap(tm);
                    desIv.setImageBitmap(bitmap);
                    if (bitmap.isRecycled())
                        bitmap.recycle();
                }
            });
        }
    
        private void layoutIv(ImageView imageView) {
            WindowManager wm = (WindowManager) getSystemService(Context.WINDOW_SERVICE);
            DisplayMetrics dm = new DisplayMetrics();
            wm.getDefaultDisplay().getMetrics(dm);
            w = (int) (dm.widthPixels / 2.0);
            h = (int) (dm.widthPixels / 2 * 37 / 48.0);
            LinearLayout.LayoutParams lp = (LinearLayout.LayoutParams) imageView.getLayoutParams();
            lp.width = w;
            lp.height = h;
            imageView.setLayoutParams(lp);
        }
    
        private Bitmap getBitmap(Bitmap bitmap) {
            initPalette(bitmap,0);
            int[] pixels = new int[w * h];
            bitmap.getPixels(pixels, 0, w, 0, 0, w, h);
    
            Bitmap resBm = Bitmap.createBitmap(w, h, Bitmap.Config.RGB_565);
            //调用c++方法处理bitmap的高密度计算  如果将循环到java代码中，h会非常耗时，而在c++中计算效率倍增
            resBm.setPixels(NdkUtils.convertBmByPixels(pixels, w, h), 0, w, 0, 0, w, h);
            initPalette(bitmap,0);
            return resBm;
        }
    
    
        /**
         * <p> Paltte的一些常用方法
         *   //1.活力颜色
         Palette.Swatch a = palette.getVibrantSwatch();
         //2.亮的活力颜色
         Palette.Swatch b=palette.getLightVibrantSwatch();
         //3.暗的活力颜色
         Palette.Swatch c = palette.getDarkVibrantSwatch();
         //4.柔色
         Palette.Swatch d = palette.getMutedSwatch();
         //5.亮的柔色
         Palette.Swatch e = palette.getLightMutedSwatch();
         //6.暗的柔色
         Palette.Swatch f = palette.getDarkMutedSwatch();
         f.getRgb(); //rgb颜色
    
         f.getTitleTextColor();//文本颜色
         //返回float[]，可以进行修改，后使用ColorUtils工具类进行转换
         f.getHsl();
         f.getBodyTextColor();//和文本颜色一样
         *
         * </p>
         * @param bitmap
         */
        private void initPalette(Bitmap  bitmap, final int type) {
    //        Palette.from(bitmap).generate(new Palette.PaletteAsyncListener() {//异步方法
    //            @Override
    //            public void onGenerated(Palette palette) {
    //                Palette.Swatch f = palette.getDarkMutedSwatch();
    //                int  rgb=f.getRgb();     //rgb颜色
    //                Log.i("TAG",type==0?"c++未处理前的RGD值=":"c++处理后的RGD值="+(rgb));
    //            }
    //        });
    
            Palette  palette=Palette.from(bitmap).generate();
            Palette.Swatch f = palette.getDarkMutedSwatch();
            int  rgb=f.getRgb();     //rgb颜色
            Log.i("TAG",type==0?"c++未处理前的RGD值=":"c++处理后的RGD值="+(rgb));
        }
    }

通过日志打印可对比Rgb值,如果写在c++里的循环放到java代码里少说得十几秒执行完毕

[70]: /images/20220530/c0d8ea5aaeb1486ab8e8a0f1dacf53a0.png