把UIColor（纯色值）对象转化成UIImage对象

+ (UIImage *)createImageWithColor:(UIColor *)color andSize:(CGSize)size
{
    CGRect rect=CGRectMake(0.0f, 0.0f, size.width, size.height);
    UIGraphicsBeginImageContext(size);
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextSetFillColorWithColor(context, [color CGColor]);
    CGContextFillRect(context, rect);

    UIImage *theImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return theImage;
}