四角切圆法

	/**
	 * 四角切圆
	 * 
	 * @param bitmap
	 *            原始位图
	 * @return 新位图
	 */
	public static Bitmap getRoundBitmap(Bitmap bitmap) {
		try {
			int width = bitmap.getWidth();
			int height = bitmap.getHeight();
			int left = 0, top = 0, right = width, bottom = height;
			float roundPx = height / 2;
			if (width > height) {
				left = (width - height) / 2;
				top = 0;
				right = left + height;
				bottom = height;
			} else if (height > width) {
				left = 0;
				top = (height - width) / 2;
				right = width;
				bottom = top + width;
				roundPx = width / 2;
			}

			Bitmap output = Bitmap.createBitmap(width, height,
					Bitmap.Config.ARGB_8888);
			if (output == null) {
				return bitmap;
			}
			Canvas canvas = new Canvas(output);
			int color = 0xff424242;
			Paint paint = new Paint();
			Rect rect = new Rect(left, top, right, bottom);
			RectF rectF = new RectF(rect);

			paint.setAntiAlias(true);
			canvas.drawARGB(0, 0, 0, 0);
			paint.setColor(color);
			canvas.drawRoundRect(rectF, roundPx, roundPx, paint);
			paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));
			canvas.drawBitmap(bitmap, rect, rect, paint);
			return output;
		} catch (Exception e) {
		}
		return bitmap;
	}