添加半透明水印

/** *  添加半透明水印 * *  @param useImage  原图 *  @param addImage  水印图片 * *  @return 有半透明水印的图片 */- (UIImage *)addWithWatermarkImg:(UIImage *)useImage addWatermarkImg:(UIImage *)addImage {    UIGraphicsBeginImageContext(useImage.size);    [useImage drawInRect:CGRectMake(0, 0, useImage.size.width, useImage.size.height)];    [addImage drawInRect:CGRectMake(0, useImage.size.height-addImage.size.height, addImage.size.width, addImage.size.height)];    UIImage *resultingImage = UIGraphicsGetImageFromCurrentImageContext();    UIGraphicsEndImageContext();    return resultingImage;}