Swift 如何将 UIColor 转换为 HEX 并在 NSLog 中显示

Swift 5:

func hexStringFromColor(color: UIColor) -> String {
    let components = color.cgColor.components
    let r: CGFloat = components?[0] ?? 0.0
    let g: CGFloat = components?[1] ?? 0.0
    let b: CGFloat = components?[2] ?? 0.0

    let hexString = String.init(format: "#%02lX%02lX%02lX", lroundf(Float(r * 255)), lroundf(Float(g * 255)), lroundf(Float(b * 255)))
    print(hexString)
    return hexString
 }

func colorWithHexString(hexString: String) -> UIColor {
    var colorString = hexString.trimmingCharacters(in: .whitespacesAndNewlines)
    colorString = colorString.replacingOccurrences(of: "#", with: "").uppercased()

    print(colorString)
    let alpha: CGFloat = 1.0
    let red: CGFloat = self.colorComponentFrom(colorString: colorString, start: 0, length: 2)
    let green: CGFloat = self.colorComponentFrom(colorString: colorString, start: 2, length: 2)
    let blue: CGFloat = self.colorComponentFrom(colorString: colorString, start: 4, length: 2)

    let color = UIColor(red: red, green: green, blue: blue, alpha: alpha)
    return color
}

func colorComponentFrom(colorString: String, start: Int, length: Int) -> CGFloat {

    let startIndex = colorString.index(colorString.startIndex, offsetBy: start)
    let endIndex = colorString.index(startIndex, offsetBy: length)
    let subString = colorString[startIndex..<endIndex]
    let fullHexString = length == 2 ? subString : "\(subString)\(subString)"
    var hexComponent: UInt32 = 0

    guard Scanner(string: String(fullHexString)).scanHexInt32(&hexComponent) else {
        return 0
    }
    let hexFloat: CGFloat = CGFloat(hexComponent)
    let floatValue: CGFloat = CGFloat(hexFloat / 255.0)
    print(floatValue)
    return floatValue
}

How to use

let red =  CGFloat(30.0)
let green =  CGFloat(171.0)
let blue =  CGFloat(13.0)
let alpha =  CGFloat(1.0)

let color = UIColor(red: CGFloat(red/255.0), green: CGFloat(green/255.0), blue: CGFloat(blue / 255.0), alpha: alpha)
let colorCode = self.hexStringFromColor(color: color)
print(colorCode)

let resultColor = self.colorWithHexString(hexString: colorCode)
print(resultColor)

目标C:

- (NSString *)hexStringFromColor:(UIColor *)color {
    const CGFloat *components = CGColorGetComponents(color.CGColor);

    CGFloat r = components[0];
    CGFloat g = components[1];
    CGFloat b = components[2];

    return [NSString stringWithFormat:@"#%02lX%02lX%02lX",
            lroundf(r * 255),
            lroundf(g * 255),
            lroundf(b * 255)];
}

获取十六进制代码字符串后，调用下面的方法获取UIColor

- (UIColor *) colorWithHexString: (NSString *) hexString
{
    NSString *colorString = [[hexString stringByReplacingOccurrencesOfString: @"#" withString: @""] uppercaseString];

    NSLog(@"colorString :%@",colorString);
    CGFloat alpha, red, blue, green;

    // #RGB
    alpha = 1.0f;
    red   = [self colorComponentFrom: colorString start: 0 length: 2];
    green = [self colorComponentFrom: colorString start: 2 length: 2];
    blue  = [self colorComponentFrom: colorString start: 4 length: 2];

    return [UIColor colorWithRed: red green: green blue: blue alpha: alpha];
}


- (CGFloat) colorComponentFrom: (NSString *) string start: (NSUInteger) start length: (NSUInteger) length {
    NSString *substring = [string substringWithRange: NSMakeRange(start, length)];
    NSString *fullHex = length == 2 ? substring : [NSString stringWithFormat: @"%@%@", substring, substring];
    unsigned hexComponent;
    [[NSScanner scannerWithString: fullHex] scanHexInt: &hexComponent];
    return hexComponent / 255.0;
}

How to use

// ( R = 30, G = 171, B = 13)? 
CGFloat red = 30.0;
CGFloat green = 171.0;
CGFloat blue = 13.0; 
CGFloat alpha = 255.0
UIColor *color = [UIColor colorWithRed:(red/255.0) green:(green/255.0) blue:(blue/255.0) alpha:(alpha/255.0)];
NSString *colorCode = [self hexStringFromColor:color];
NSLog(@"Color Code: %@", colorCode);

UIColor *resultColor = [self colorWithHexString:colorCode];