Android 图片特效

     <p>在Android上使用JAVA实现彩图转换为灰度图，跟J2ME上的实现类似，不过遇到频繁地转换或者是大图转换时，就必须使用NDK来提高速度了。本文主要通过JAVA和NDK这两种方式来分别实现彩图转换为灰度图，并给出速度的对比。</p>    <p><strong>从转换灰度图的耗时来说，NDK的确比JAVA所用的时间短不少。</strong><br /> </p>    <pre class="brush:xml; toolbar: true; auto-links: false;"><?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> </pre>    <p></p> 主程序demo.java的源码如下：    <pre class="brush:java; toolbar: true; auto-links: false;">package eoe.demo;    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;  }  } </pre>    <p></p> 封装NDK函数的JAVA类LibFuns.java的源码如下    <pre class="brush:java; toolbar: true; auto-links: false;">package eoe.demo;  public class LibFuns {  static {  System.loadLibrary("Imgdemo");  }  /**  * @param宽度当前视图的宽度 * @param高度当前视图的高度 */  public static native int[] ImgToGray(int[] buf, int w, int h);  } </pre>    <p></p> 彩图转换为灰度图的Imgdemo.cpp源码:    <pre class="brush:cpp; toolbar: true; auto-links: false;">#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;  } </pre>    <p></p> Android.mk的源码：    <pre class="brush:shell; toolbar: true; auto-links: false;">LOCAL_PATH:= $(call my-dir)  include $(CLEAR_VARS)  LOCAL_MODULE := ImgToGray  LOCAL_SRC_FILES := ImgToGray.cpp  include $(BUILD_SHARED_LIBRARY) </pre>