Android中有很多圖片特效處理技巧，比如圓角、倒影，今天為大家分享一個例項，本例主要是先獲取桌布(getWallpaper()),然後對當前桌布的一些特效處理。

　　第一步:新建一個Android工程命名為ImageDemo,工程結構如下:

　　第二步:新建一個.java檔案,命名為ImageUtil.java,在裡面定義一些圖片處理方法,程式碼如下:
　　
　　Java程式碼:
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package com.android.tutor; 
import android.graphics.Bitmap; 
import android.graphics.Canvas; 
import android.graphics.LinearGradient; 
import android.graphics.Matrix; 
import android.graphics.Paint; 
import android.graphics.PixelFormat; 
import android.graphics.PorterDuffXfermode; 
import android.graphics.Rect; 
import android.graphics.RectF; 
import android.graphics.Bitmap.Config; 
import android.graphics.PorterDuff.Mode; 
import android.graphics.Shader.TileMode; 
import android.graphics.drawable.Drawable; 
public class ImageUtil {

//放大縮小圖片 
public static Bitmap zoomBitmap(Bitmap bitmap,int w,int h){ 
int width = bitmap.getWidth(); 
int height = bitmap.getHeight(); 
Matrix matrix = new Matrix(); 
float scaleWidht = ((float)w / width); 
float scaleHeight = ((float)h / height); 
matrix.postScale(scaleWidht, scaleHeight); 
Bitmap newbmp = Bitmap.createBitmap(bitmap, 0, 0, width, height, matrix, true); 
return newbmp; 
} 
//將Drawable轉化為Bitmap 
public static Bitmap drawableToBitmap(Drawable drawable){ 
int width = drawable.getIntrinsicWidth(); 
int height = drawable.getIntrinsicHeight(); 
Bitmap bitmap = Bitmap.createBitmap(width, height, 
drawable.getOpacity() != PixelFormat.OPAQUE ? Bitmap.Config.ARGB_8888 
: Bitmap.Config.RGB_565); 
Canvas canvas = new Canvas(bitmap); 
drawable.setBounds(0,0,width,height); 
drawable.draw(canvas); 
return bitmap;

}

//獲得圓角圖片的方法 
public static Bitmap getRoundedCornerBitmap(Bitmap bitmap,float roundPx){

Bitmap output = Bitmap.createBitmap(bitmap.getWidth(), bitmap 
.getHeight(), Config.ARGB_8888); 
Canvas canvas = new Canvas(output);

final int color = 0xff424242; 
final Paint paint = new Paint(); 
final Rect rect = new Rect(0, 0, bitmap.getWidth(), bitmap.getHeight()); 
final RectF rectF = new RectF(rect);

paint.setAntiAlias(true); 
canvas.drawARGB(0, 0, 0, 0); 
paint.setColor(color); 
canvas.drawRoundRect(rectF, roundPx, roundPx, paint);

paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN)); 
canvas.drawBitmap(bitmap, rect, rect, paint);

return output; 
} 
//獲得帶倒影的圖片方法 
public static Bitmap createReflectionImageWithOrigin(Bitmap bitmap){ 
final int reflectionGap = 4; 
int width = bitmap.getWidth(); 
int height = bitmap.getHeight();

Matrix matrix = new Matrix(); 
matrix.preScale(1, -1);

Bitmap reflectionImage = Bitmap.createBitmap(bitmap, 
0, height/2, width, height/2, matrix, false);

Bitmap bitmapWithReflection = Bitmap.createBitmap(width, (height + height/2), Config.ARGB_8888);

Canvas canvas = new Canvas(bitmapWithReflection); 
canvas.drawBitmap(bitmap, 0, 0, null); 
Paint deafalutPaint = new Paint(); 
canvas.drawRect(0, height,width,height + reflectionGap, 
deafalutPaint);

canvas.drawBitmap(reflectionImage, 0, height + reflectionGap, null);

Paint paint = new Paint(); 
LinearGradient shader = new LinearGradient(0, 
bitmap.getHeight(), 0, bitmapWithReflection.getHeight() 
+ reflectionGap, 0x70ffffff, 0x00ffffff, TileMode.CLAMP); 
paint.setShader(shader); 
// Set the Transfer mode to be porter duff and destination in 
paint.setXfermode(new PorterDuffXfermode(Mode.DST_IN)); 
// Draw a rectangle using the paint with our linear gradient 
canvas.drawRect(0, height, width, bitmapWithReflection.getHeight() 
+ reflectionGap, paint);

return bitmapWithReflection; 
}

}

　　第三步:修改main.xml佈局檔案,主要放了兩個ImageView控制元件,程式碼如下:
　　
　　Java程式碼:
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<?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" 
> 
<ImageView 
android:id="@+id/image01" 
android:layout_width="wrap_content" 
android:layout_height="wrap_content" 
android:padding="10px" 
/> 
<ImageView 
android:id="@+id/image02" 
android:layout_width="wrap_content" 
android:layout_height="wrap_content" 
android:padding="10px" 
/> 
</LinearLayout>

　　第四步:修改主核心程式,ImageDemo.java,程式碼如下:
　　
　　Java程式碼:
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package com.android.tutor; 
import android.app.Activity; 
import android.graphics.Bitmap; 
import android.graphics.drawable.Drawable; 
import android.os.Bundle; 
import android.widget.ImageView; 
public class Imagedemo extends Activity { 
private ImageView mImageView01,mImageView02;

public void onCreate(Bundle savedInstanceState) { 
super.onCreate(savedInstanceState); 
setContentView(R.layout.main); 
setupViews(); 
}

private void setupViews(){ 
mImageView01 = (ImageView)findViewById(R.id.image01); 
mImageView02 = (ImageView)findViewById(R.id.image02);

//獲取桌布返回值是Drawable 
Drawable drawable = getWallpaper(); 
//將Drawable轉化為Bitmap 
Bitmap bitmap = ImageUtil.drawableToBitmap(drawable); 
//縮放圖片 
Bitmap zoomBitmap = ImageUtil.zoomBitmap(bitmap, 100, 100); 
//獲取圓角圖片 
Bitmap roundBitmap = ImageUtil.getRoundedCornerBitmap(zoomBitmap, 10.0f); 
//獲取倒影圖片 
Bitmap reflectBitmap = ImageUtil.createReflectionImageWithOrigin(zoomBitmap); 
//這裡可以讓Bitmap再轉化為Drawable 
// Drawable roundDrawable = new BitmapDrawable(roundBitmap); 
// Drawable reflectDrawable = new BitmapDrawable(reflectBitmap); 
// mImageView01.setBackgroundDrawable(roundDrawable); 
// mImageView02.setBackgroundDrawable(reflectDrawable);

mImageView01.setImageBitmap(roundBitmap); 
mImageView02.setImageBitmap(reflectBitmap); 
}

}

　　第五步:執行上述工程,檢視效果如下: