Android提高之使用NDK把彩图转换灰度图的方法

<?xml version="1.0" encoding="utf-8" ?>  
- <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent"> 
<Button android:layout_height="wrap_content" android:layout_width="fill_parent" android:id="@+id/btnJAVA" android:text="使用JAVA转换灰度图" />  
<Button android:layout_height="wrap_content" android:layout_width="fill_parent" android:id="@+id/btnNDK" android:text="使用NDK转换灰度图" />  
<ImageView android:id="@+id/ImageView01" android:layout_width="fill_parent" android:layout_height="fill_parent" />  
</LinearLayout> 

package com.testToGray; 
import android.app.Activity; 
import android.graphics.Bitmap; 
import android.graphics.Bitmap.Config; 
import android.graphics.drawable.BitmapDrawable; 
import android.os.Bundle; 
import android.view.View; 
import android.widget.Button; 
import android.widget.ImageView; 
public class testToGray extends Activity { 
  /** Called when the activity is first created. */ 
  Button btnJAVA,btnNDK; 
  ImageView imgView; 
  @Override 
  public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.main); 
    this.setTitle("使用NDK转换灰度图---hellogv"); 
    btnJAVA=(Button)this.findViewById(R.id.btnJAVA); 
    btnJAVA.setOnClickListener(new ClickEvent()); 
     
    btnNDK=(Button)this.findViewById(R.id.btnNDK); 
    btnNDK.setOnClickListener(new ClickEvent()); 
    imgView=(ImageView)this.findViewById(R.id.ImageView01); 
  } 
  class ClickEvent implements View.OnClickListener{ 
    @Override 
    public void onClick(View v) { 
      if(v==btnJAVA) 
      { 
        long current=System.currentTimeMillis(); 
        Bitmap img=ConvertGrayImg(R.drawable.cat); 
        long performance=System.currentTimeMillis()-current; 
        //显示灰度图 
        imgView.setImageBitmap(img); 
        testToGray.this.setTitle("w:"+String.valueOf(img.getWidth())+",h:"+String.valueOf(img.getHeight()) 
            +" JAVA耗时 "+String.valueOf(performance)+" 毫秒"); 
      } 
      else if(v==btnNDK) 
      { 
        long current=System.currentTimeMillis(); 
        //先打开图像并读取像素 
        Bitmap img1=((BitmapDrawable) getResources().getDrawable(R.drawable.cat)).getBitmap(); 
        int w=img1.getWidth(),h=img1.getHeight(); 
        int[] pix = new int[w * h]; 
        img1.getPixels(pix, 0, w, 0, 0, w, h); 
        //通过ImgToGray.so把彩色像素转为灰度像素 
        int[] resultInt=LibFuns.ImgToGray(pix, w, h); 
        Bitmap resultImg=Bitmap.createBitmap(w, h, Config.RGB_565); 
        resultImg.setPixels(resultInt, 0, w, 0, 0,w, h); 
        long performance=System.currentTimeMillis()-current; 
        //显示灰度图 
        imgView.setImageBitmap(resultImg); 
        testToGray.this.setTitle("w:"+String.valueOf(img1.getWidth())+",h:"+String.valueOf(img1.getHeight()) 
            +" NDK耗时 "+String.valueOf(performance)+" 毫秒"); 
      } 
    } 
  } 
   
  /** 
   * 把资源图片转为灰度图 
   * @param resID 资源ID 
   * @return 
   */ 
  public Bitmap ConvertGrayImg(int resID) 
  { 
    Bitmap img1=((BitmapDrawable) getResources().getDrawable(resID)).getBitmap(); 
     
    int w=img1.getWidth(),h=img1.getHeight(); 
    int[] pix = new int[w * h]; 
    img1.getPixels(pix, 0, w, 0, 0, w, h); 
    int alpha=0xFF<<24; 
    for (int i = 0; i < h; i++) {  
      for (int j = 0; j < w; j++) {  
        // 获得像素的颜色  
        int color = pix[w * i + j];  
        int red = ((color & 0x00FF0000) >> 16);  
        int green = ((color & 0x0000FF00) >> 8);  
        int blue = color & 0x000000FF;  
        color = (red + green + blue)/3;  
        color = alpha | (color << 16) | (color << 8) | color;  
        pix[w * i + j] = color; 
      } 
    } 
    Bitmap result=Bitmap.createBitmap(w, h, Config.RGB_565); 
    result.setPixels(pix, 0, w, 0, 0,w, h); 
    return result; 
  } 
}

package com.testToGray; 
public class LibFuns { 
  static { 
    System.loadLibrary("ImgToGray"); 
  } 
  /** 
  * @param width the current view width 
  * @param height the current view height 
  */ 
  public static native int[] ImgToGray(int[] buf, int w, int h); 
}

#include <jni.h> 
#include <stdio.h> 
#include <stdlib.h> 
extern "C" { 
JNIEXPORT jintArray JNICALL Java_com_testToGray_LibFuns_ImgToGray( 
    JNIEnv* env, jobject obj, jintArray buf, int w, int h); 
} 
; 
JNIEXPORT jintArray JNICALL Java_com_testToGray_LibFuns_ImgToGray( 
    JNIEnv* env, jobject obj, jintArray buf, int w, int h) { 
  jint *cbuf; 
  cbuf = env->GetIntArrayElements(buf, false); 
  if (cbuf == NULL) { 
    return 0; /* exception occurred */ 
  } 
  int alpha = 0xFF << 24; 
  for (int i = 0; i < h; i++) { 
    for (int j = 0; j < w; j++) { 
      // 获得像素的颜色 
      int color = cbuf[w * i + j]; 
      int red = ((color & 0x00FF0000) >> 16); 
      int green = ((color & 0x0000FF00) >> 8); 
      int blue = color & 0x000000FF; 
      color = (red + green + blue) / 3; 
      color = alpha | (color << 16) | (color << 8) | color; 
      cbuf[w * i + j] = color; 
    } 
  } 
  int size=w * h; 
  jintArray result = env->NewIntArray(size); 
  env->SetIntArrayRegion(result, 0, size, cbuf); 
  env->ReleaseIntArrayElements(buf, cbuf, 0); 
  return result; 
}

LOCAL_PATH:= $(call my-dir) 
include $(CLEAR_VARS) 
LOCAL_MODULE  := ImgToGray 
LOCAL_SRC_FILES := ImgToGray.cpp 
include $(BUILD_SHARED_LIBRARY)