Java实现图片倒影代码

/*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; 
    } 
}