Android中实现图片倒影的代码

/*实现图片倒影(tested)*/
public class ButtonImageActivity extends Activity {
    /** Called when the activity is first created. */
    private ImageView image_btn;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        image_btn=(ImageView)findViewById(R.id.image_btn);
        Bitmap bitmap =((BitmapDrawable)getResources().getDrawable(R.drawable.image_btn)).getBitmap();
        image_btn.setImageBitmap(createReflectedImage(bitmap));
        image_btn.setOnClickListener(new OnClickListener() {

            public void onClick(View v) {
                // TODO Auto-generated method stub

            }
        });
    }
    private Bitmap createReflectedImage(Bitmap originalBitmap) {  
        // 图片与倒影间隔距离  
        final int reflectionGap = 4;  

        // 图片的宽度  
        int width = originalBitmap.getWidth();  
        // 图片的高度  
        int height = originalBitmap.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 reflectionBitmap = Bitmap.createBitmap(originalBitmap,height / 2,width,matrix,false);  
        // 创建标准的Bitmap对象，宽和原图一致，高是原图的1.5倍。  
        Bitmap withReflectionBitmap = Bitmap.createBitmap(width,(height  
                + height / 2 + reflectionGap),Config.ARGB_8888);  

        // 构造函数传入Bitmap对象，为了在图片上画图  
        Canvas canvas = new Canvas(withReflectionBitmap);  
        // 画原始图片  
        canvas.drawBitmap(originalBitmap,null);  

        // 画间隔矩形  
        Paint defaultPaint = new Paint();  
        canvas.drawRect(0,height,height + reflectionGap,defaultPaint);  

        // 画倒影图片  
        canvas.drawBitmap(reflectionBitmap,null);  

        // 实现倒影效果  
        Paint paint = new Paint();  
        LinearGradient shader = new LinearGradient(0,originalBitmap.getHeight(),withReflectionBitmap.getHeight(),0x70ffffff,0x00ffffff,TileMode.MIRROR);  
        paint.setShader(shader);  
        paint.setXfermode(new PorterDuffXfermode(Mode.DST_IN));  

        // 覆盖效果  
        canvas.drawRect(0,paint);  

        return withReflectionBitmap;  
    }  
}