* @exception IllegalArgumentException
	 *                <ul>
	 *                <li>ERROR_NULL_ARGUMENT - if pixels is null</li>
	 *                <li>ERROR_INVALID_ARGUMENT - if x or y is out of bounds</li>
	 *                <li>ERROR_INVALID_ARGUMENT - if putWidth is negative</li>
	 *                </ul>
	 */
	public void setAlphas(int x, int y, int putWidth, byte[] alphas,
			int startIndex) {
		if (alphas == null)
			SWT.error(SWT.ERROR_NULL_ARGUMENT);
		if (putWidth < 0 || x >= width || y >= height || x < 0 || y < 0)
			SWT.error(SWT.ERROR_INVALID_ARGUMENT);
		if (putWidth == 0)
			return;

		if (alphaData == null)
			alphaData = new byte[width * height];
		// may throw an IndexOutOfBoundsException
		System.arraycopy(alphas, startIndex, alphaData, y * width + x, putWidth);
	}