Bitamp生成倒影

main.activity如下:

package c.c;
import android.os.Bundle;
import android.widget.ImageView;
import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.LinearGradient;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.PorterDuff.Mode;
import android.graphics.PorterDuffXfermode;
import android.graphics.Shader.TileMode;
/**
 * Demo:生成Bitmap的倒影
 */
public class MainActivity extends Activity {
	private ImageView mImageView;
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
		mImageView=(ImageView) findViewById(R.id.imageView);
		Bitmap rawBitmap=BitmapFactory.decodeResource(getResources(), R.drawable.a);
		Bitmap newBitmap=getBitmapReflection(rawBitmap);
		mImageView.setImageBitmap(newBitmap);
	}

	private Bitmap getBitmapReflection(Bitmap rawBitmap) {
		final int gap = 4;
		int width = rawBitmap.getWidth();
		int height = rawBitmap.getHeight();
		Matrix matrix = new Matrix();
		//逆置
		matrix.preScale(1, -1);
		//倒影
		Bitmap reflectionBitmap =
		Bitmap.createBitmap(rawBitmap, 0, height/2,width, height/2, matrix, false);
		//带有倒影的图片
		Bitmap bitmapWithReflection =
		Bitmap.createBitmap(width,(height + height/2), Config.ARGB_8888);

		Canvas canvas = new Canvas(bitmapWithReflection);

		//画原图
		canvas.drawBitmap(rawBitmap, 0, 0, null);
		Paint paint=new Paint();
		//画分界线
		canvas.drawRect(0, height, width, height + gap, paint);
		//画倒影
		canvas.drawBitmap(reflectionBitmap, 0, height + gap, null);
		//沿Y轴渐变效果
		LinearGradient shader =
		new LinearGradient(0, rawBitmap.getHeight(), 0,
		bitmapWithReflection.getHeight() + gap, 0x70ffffff,0x00ffffff, TileMode.CLAMP);
		paint.setShader(shader);
		//因为有两层(倒影层和渐变),所以设置过渡模式
		paint.setXfermode(new PorterDuffXfermode(Mode.DST_IN));
		//画一个具有渐变效果的矩形
		canvas.drawRect(0, height, width, bitmapWithReflection.getHeight()+ gap, paint);
		return bitmapWithReflection;
	}	

}

main.xml如下:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity" >

    <ImageView
        android:id="@+id/imageView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true"
      />

</RelativeLayout>