oc 顏色轉換 16進制 轉換成RGB

OC 顏色使用基本都是RGB的，我們通常還習慣使用16進製表示顏色，但是OC沒有直接可以使用的方法，通常使用工具類來轉換一下：

#define DEFAULT_VOID_COLOR [UIColor whiteColor]
+ (UIColor *)colorWithHexString:(NSString *)stringToConvert
{
    NSString *cString = [[stringToConvert stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]] uppercaseString];
    
    
    if ([cString length] < 6)
        return DEFAULT_VOID_COLOR;
    if ([cString hasPrefix:@"#"])
        cString = [cString substringFromIndex:1];
    if ([cString length] != 6)
        return DEFAULT_VOID_COLOR;
    
    NSRange range;
    range.location = 0;
    range.length = 2;
    NSString *rString = [cString substringWithRange:range];
    
    range.location = 2;
    NSString *gString = [cString substringWithRange:range];
    
    range.location = 4;
    NSString *bString = [cString substringWithRange:range];
    
    
    unsigned int r, g, b;
    [[NSScanner scannerWithString:rString] scanHexInt:&r];
    [[NSScanner scannerWithString:gString] scanHexInt:&g];
    [[NSScanner scannerWithString:bString] scanHexInt:&b];
    
    return [UIColor colorWithRed:((float) r / 255.0f)
                           green:((float) g / 255.0f)
                            blue:((float) b / 255.0f)
                           alpha:1.0f];
}