为Bitmap添加圆角

public static Bitmap getRoundedCornerBitmap(Bitmap bitmap) {

    Bitmap utput = Bitmap.createBitmap(bitmap.getWidth(),
    bitmap.getHeight(), Config.ARGB_8888);
    //得到画布
    Canvas canvas = new Canvas(output);
    //将画布的四角圆化
    final int color = Color.RED;
    final Paint paint = new Paint();
    //得到与图像相同大小的区域 由构造的四个值决定区域的位置以及大小
    final Rect rect = new Rect(0, 0, bitmap.getWidth(), bitmap.getHeight());
    final RectF rectF = new RectF(rect);
    //值越大角度越明显
    final float roundPx = 50;
    paint.setAntiAlias(true);
    canvas.drawARGB(0, 0, 0, 0);
    paint.setColor(color);
    //drawRoundRect的第2,3个参数一样则画的是正圆的一角，如果数值不同则是椭圆的一角
    canvas.drawRoundRect(rectF, roundPx,roundPx, paint);
    paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));
    canvas.drawBitmap(bitmap, rect, rect, paint);
    return output;
    }