如何去掉searchBar的背景色

//取消searchbar背景色

[self imageWithColor:[UIColor clearColor] size:_searchBar.bounds.size];

- (UIImage *)imageWithColor:(UIColor *)color size:(CGSize)size

{

CGRect rect = CGRectMake(0, 0, size.width, size.height);

UIGraphicsBeginImageContext(rect.size);

CGContextRef context = UIGraphicsGetCurrentContext();

CGContextSetFillColorWithColor(context, [color CGColor]);

CGContextFillRect(context, rect);

UIImage *image = UIGraphicsGetImageFromCurrentImageContext();

UIGraphicsEndImageContext();

return image;

}