很好的一篇文章，如何实现图片倒影的效果

package com.lp.imageUI;  
  
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 {  
      
    //放大缩小图片  
    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;  
    }  
    //将Drawable转化为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;  
              
        }  
       
     //获得圆角图片的方法  
    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);  
        /** 
         * 画一个圆角矩形 
         * rectF: 矩形 
         * roundPx 圆角在x轴上或y轴上的半径 
         */  
        canvas.drawRoundRect(rectF, roundPx, roundPx+10, paint);  
        //设置两张图片相交时的模式  
        //setXfermode前的是 dst 之后的是src  
        //在正常的情况下，在已有的图像上绘图将会在其上面添加一层新的形状。   
        //如果新的Paint是完全不透明的，那么它将完全遮挡住下面的Paint；  
        //PorterDuffXfermode就可以来解决这个问题  
        //canvas原有的图片 可以理解为背景 就是dst  
        //新画上去的图片 可以理解为前景 就是src  
//      paint.setXfermode(new PorterDuffXfermode(Mode.SRC_OUT));  
        paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));  
        canvas.drawBitmap(bitmap, rect, rect, paint);  
   
        return output;  
    }  
    //获得带倒影的图片方法  
    public static Bitmap createReflectionImageWithOrigin(Bitmap bitmap){  
        // 图片与倒影间隔距离    
        final int reflectionGap = 4;  
        // 图片的宽度    
        int width = bitmap.getWidth();  
         // 图片的高度    
        int height = bitmap.getHeight();  
          
        Matrix matrix = new Matrix();  
        // 图片缩放，x轴变为原来的1倍，y轴为-1倍,实现图片的反转  
        matrix.preScale(1, -1);  
        // 创建反转后的图片Bitmap对象，图片高是原图的一半。    
        Bitmap reflectionImage = Bitmap.createBitmap(bitmap,   
                0, height/2, width, height/2, matrix, false);  
        // 创建标准的Bitmap对象，宽和原图一致，高是原图的1.5倍。 可以理解为这张图将会在屏幕上显示 是原图和倒影的合体    
        Bitmap bitmapWithReflection = Bitmap.createBitmap(width, (height + height/2), Config.ARGB_8888);  
         // 构造函数传入Bitmap对象，为了在图片上画图    
        Canvas canvas = new Canvas(bitmapWithReflection);  
        // 画原始图片    
        canvas.drawBitmap(bitmap, 0, 0, null);  
        // 画间隔矩形    
        Paint deafalutPaint = new Paint();  
        canvas.drawRect(0, height,width,height + reflectionGap,  
                deafalutPaint);  
        // 画倒影图片    
        canvas.drawBitmap(reflectionImage, 0, height + reflectionGap, null);  
        // 实现倒影渐变效果    
        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  
        // 覆盖效果    
        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;  
    }  
      
}