Java实现图片倒影代码详解编程语言

/*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, 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。  
        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, 0, 0, null);  
     
        // 画间隔矩形  
        Paint defaultPaint = new Paint();  
        canvas.drawRect(0, height, width, height + reflectionGap, defaultPaint);  
     
        // 画倒影图片  
        canvas.drawBitmap(reflectionBitmap, 0, height + reflectionGap, null);  
     
        // 实现倒影效果  
        Paint paint = new Paint();  
        LinearGradient shader = new LinearGradient(0, originalBitmap.getHeight(),   
                0, withReflectionBitmap.getHeight(), 0x70ffffff, 0x00ffffff,  
                TileMode.MIRROR);  
        paint.setShader(shader);  
        paint.setXfermode(new PorterDuffXfermode(Mode.DST_IN));  
     
        // 覆盖效果  
        canvas.drawRect(0, height, width, withReflectionBitmap.getHeight(), paint);  
     
        return withReflectionBitmap;  
    }  
}