2018.9.19

一个简单的宏定义

宏定义可以直接将16进制的颜色值转成对应的UIColor对象；

#define UIColorFromRGBA(rgbValue, alpha) [UIColor colorWithRed:((float)((rgbValue & 0xFF0000) >> 16))/255.0 green:((float)((rgbValue & 0xFF00) >> 8))/255.0 blue:((float)(rgbValue & 0xFF))/255.0 alpha:alpha]

HexString 转 UIColor

支持前缀 0x，# 标识，支持 带透明度的8位长度字符串 和 不带透明度的6位字符串，代码扫一眼就明白了；嗯，方便起见建议写入UIColor的分类中；

+ (UIColor *)ColorWithHexString:(NSString *)color {
    return [UIColor ColorwithHexString:color Alpha:-1];
}

自定义当前转换颜色的 透明度，若Alpha的值小于0，则表明放弃自定义透明度的操作；

+ (UIColor *)ColorwithHexString:(NSString *)color Alpha:(CGFloat)alpha {
    NSString *cString = [[color stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]] uppercaseString];
    // String should be 6 or 8 characters
    if ([cString length] < 6) {
        return [UIColor clearColor];
    }

    // strip 0X if it appears
    if ([cString hasPrefix:@"0X"])
        cString = [cString substringFromIndex:2];
    if ([cString hasPrefix:@"#"])
        cString = [cString substringFromIndex:1];
    if ([cString length] != 8 && [cString length]!=6)
        return [UIColor clearColor];

    CGFloat insideAlpha = 1.0f;
    if ([cString length]==8) {
        NSString *aString = [cString substringWithRange:NSMakeRange(0, 2)];
        unsigned int a;
        [[NSScanner scannerWithString:aString] scanHexInt:&a];
        insideAlpha = (float)a / 255.0f;
        cString =  [cString substringWithRange:NSMakeRange(2, 6)];
    }
    if (alpha>0) {
        insideAlpha = alpha;
    }

    // Separate into r, g, b substrings
    NSRange range;
    range.location = 0;
    range.length = 2;

    //r
    NSString *rString = [cString substringWithRange:range];

    //g
    range.location = 2;
    NSString *gString = [cString substringWithRange:range];

    //b
    range.location = 4;
    NSString *bString = [cString substringWithRange:range];

    // Scan values
    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:insideAlpha];
}

UIColor 转 HexString

转换完毕的字符串不含任何前缀，如有需要，请自行拼接0x，# 等惯用前缀；另，HasAlpha参数决定是否将传入UIColor的透明度也计算入结果字符串，同样的，扫一眼代码就明白了；嗯，方便起见建议写入UIColor的分类中；

+ (NSString *)HexStringWithColor:(UIColor *)color HasAlpha:(BOOL)hasAlpha {
    CGFloat r, g, b, a;
    [color getRed:&r green:&g blue:&b alpha:&a];
    int rgb = (int)(r * 255.0f)<<16 | (int)(g * 255.0f)<<8 | (int)(b * 255.0f)<<0;
    if (hasAlpha) {
        rgb = (int)(a * 255.0f)<<24 | (int)(r * 255.0f)<<16 | (int)(g * 255.0f)<<8 | (int)(b * 255.0f)<<0;
    }

    return [NSString stringWithFormat:@"%06x", rgb];
}

最后来个简单示例

- (void)viewDidLoad {
    [super viewDidLoad];

    UIView *sampleView = [[UIView alloc] initWithFrame:self.view.bounds];
    [self.view addSubview:sampleView];
    //sampleView.backgroundColor = UIColorFromRGBA(0x00a47b, 1.0f);
    sampleView.backgroundColor = [UIColor ColorWithHexString:@"0x6700a47b"];
    NSString *sampleStr = [UIColor HexStringWithColor:sampleView.backgroundColor HasAlpha:YES ];
    NSLog(@"%@", sampleStr);
}