android剪切成圓形圖檔CircleBitmap

/**
	 * 生成透明背景的圓形圖檔,！注意要生成透明背景的圓形，圖檔一定要png類型的，不能是jpg類型
	 * 
	 * @param bitmap
	 * @return
	 */
	public Bitmap getCircleBitmap(Bitmap bitmap) {
		if (bitmap == null) {
			return null;
		}
		try {
			Bitmap circleBitmap = Bitmap.createBitmap(bitmap.getWidth(),
					bitmap.getHeight(), Config.ARGB_8888);
			Canvas canvas = new Canvas(circleBitmap);
			final Paint paint = new Paint();
			final Rect rect = new Rect(0, 0, bitmap.getWidth(),
					bitmap.getHeight());
			final RectF rectF = new RectF(new Rect(0, 0, bitmap.getWidth(),
					bitmap.getHeight()));
			float roundPx = 0.0f;
			// 以較短的邊為标準
			if (bitmap.getWidth() > bitmap.getHeight()) {
				roundPx = bitmap.getHeight() / 2.0f;
			} else {
				roundPx = bitmap.getWidth() / 2.0f;
			}
			paint.setAntiAlias(true);
			canvas.drawARGB(0, 0, 0, 0);
			paint.setColor(Color.WHITE);
			canvas.drawRoundRect(rectF, roundPx, roundPx, paint);
			paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));
			final Rect src = new Rect(0, 0, bitmap.getWidth(),
					bitmap.getHeight());
			canvas.drawBitmap(bitmap, src, rect, paint);
			return circleBitmap;
		} catch (Exception e) {
			return bitmap;
		}
	}