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;
}

}