如何在Objective-C中将RGB十六进制字符串转换成UIColor？

Question

我有一个包含颜色值的URL，格式如下："#ff33cc"。我想将这个值转换为UIColor。我试着用下面的代码，但是无法正确获取baseColor1的值。看起来我应该去掉#字符。有没有其他方法可以实现？

NSScanner *scanner2 = [NSScanner scannerWithString:@"#ff33cc"];
int baseColor1;
[scanner2 scanHexInt:&baseColor1]; 
CGFloat red = (baseColor1 & 0xFF0000);
[UIColor colorWithRed:red ...

- dipu

---

根据文档，-(BOOL)scanHexInt:(unsigned *)intValue，所以您可能希望将baseColor声明为unsigned; 除此之外，我喜欢progrmr的答案。 - Isaac

Answer 1

你离正确还很近，但是colorWithRed:green:blue:alpha:函数需要的值范围在0.0到1.0之间，因此你需要将位数右移并除以255.0f：

CGFloat red   = ((baseColor1 & 0xFF0000) >> 16) / 255.0f;
CGFloat green = ((baseColor1 & 0x00FF00) >>  8) / 255.0f;
CGFloat blue  =  (baseColor1 & 0x0000FF) / 255.0f;

编辑 - 此外，NSScanner的scanHexInt将跳过十六进制字符串前面的0x，但我认为它不会跳过在你的十六进制字符串前面的#字符。您可以添加以下行来处理：

[scanner2 setCharactersToBeSkipped:[NSCharacterSet symbolCharacterSet]]; 

- progrmr

Answer 2

我添加了一个字符串替换函数，使其可以接受包含或不包含 # 的十六进制字符串。

可能的完整代码：

+ (UIColor *)colorWithHexString:(NSString *)stringToConvert
{
    NSString *noHashString = [stringToConvert stringByReplacingOccurrencesOfString:@"#" withString:@""]; // remove the #
    NSScanner *scanner = [NSScanner scannerWithString:noHashString];
    [scanner setCharactersToBeSkipped:[NSCharacterSet symbolCharacterSet]]; // remove + and $

    unsigned hex;
    if (![scanner scanHexInt:&hex]) return nil;
    int r = (hex >> 16) & 0xFF;
    int g = (hex >> 8) & 0xFF;
    int b = (hex) & 0xFF;

    return [UIColor colorWithRed:r / 255.0f green:g / 255.0f blue:b / 255.0f alpha:1.0f];
}

- Lucien

---

这很棒，谢谢。但是，在扫描器上设置charactersToBeSkipped不已经规避了对#字符串替换的需要了吗？ - devios1

Answer 3

我已经编写了一个函数，可以处理以下情况： 1）带或不带 # 2）3个或6个字符的值，如 #000 或 #000000 3）如果超过六个数字，则忽略多余的数字。

//Function Call
UIColor *organizationColor = [self colorWithHexString:@"#AAAAAAAAAAAAA" alpha:1];

//Function
- (UIColor *)colorWithHexString:(NSString *)str_HEX  alpha:(CGFloat)alpha_range{
    NSString *noHashString = [str_HEX stringByReplacingOccurrencesOfString:@"#" withString:@""]; // remove the #

    int red = 0;
    int green = 0;
    int blue = 0;

if ([str_HEX length]<=3)
    {
        sscanf([noHashString UTF8String], "%01X%01X%01X", &red, &green, &blue);
        return  [UIColor colorWithRed:red/16.0 green:green/16.0 blue:blue/16.0 alpha:alpha_range];
    }
else if ([str_HEX length]>7)
    {
        NSString *mySmallerString = [noHashString substringToIndex:6];
        sscanf([mySmallerString UTF8String], "%02X%02X%02X", &red, &green, &blue);
        return  [UIColor colorWithRed:red/255.0 green:green/255.0 blue:blue/255.0 alpha:alpha_range];
    }
else
{
    sscanf([noHashString UTF8String], "%02X%02X%02X", &red, &green, &blue);
    return  [UIColor colorWithRed:red/255.0 green:green/255.0 blue:blue/255.0 alpha:alpha_range];
}}

- Md. Ibrahim Hassan

Answer 4

Swift

它非常有用

extension UIColor {

    convenience init(hexString: String) {
        let hex = hexString.trimmingCharacters(in: CharacterSet.alphanumerics.inverted)
        var int = UInt32()
        Scanner(string: hex).scanHexInt32(&int)
        let a, r, g, b: UInt32
        switch hex.count {
        case 3: // RGB (12-bit)
            (a, r, g, b) = (255, (int >> 8) * 17, (int >> 4 & 0xF) * 17, (int & 0xF) * 17)
        case 6: // RGB (24-bit)
            (a, r, g, b) = (255, int >> 16, int >> 8 & 0xFF, int & 0xFF)
        case 8: // ARGB (32-bit)
            (a, r, g, b) = (int >> 24, int >> 16 & 0xFF, int >> 8 & 0xFF, int & 0xFF)
        default:
            (a, r, g, b) = (1, 1, 1, 0)
        }
        self.init(red: CGFloat(r) / 255, green: CGFloat(g) / 255, blue: CGFloat(b) / 255, alpha: CGFloat(a) / 255)
    }

    public func hexStringWithAlpha(_ includeAlpha: Bool) -> String {
        var r: CGFloat = 0
        var g: CGFloat = 0
        var b: CGFloat = 0
        var a: CGFloat = 0
        self.getRed(&r, green: &g, blue: &b, alpha: &a)

        if (includeAlpha) {
            return String(format: "%02X%02X%02X%02X", Int(r * 255), Int(g * 255), Int(b * 255), Int(a * 255))
        } else {
            return String(format: "%02X%02X%02X", Int(r * 255), Int(g * 255), Int(b * 255))
        }
    }

    open override var description: String {
        return self.hexStringWithAlpha(true)
    }

    open override var debugDescription: String {
        return self.hexStringWithAlpha(true)
    }
}

Obj-C，即Objective-C。

UIColor *organizationColor = [self colorWithHexString:@"#ababab" alpha:1];


- (UIColor *)colorWithHexString:(NSString *)str_HEX  alpha:(CGFloat)alpha_range{
    int red = 0;
    int green = 0;
    int blue = 0;
    sscanf([str_HEX UTF8String], "#%02X%02X%02X", &red, &green, &blue);
    return  [UIColor colorWithRed:red/255.0 green:green/255.0 blue:blue/255.0 alpha:alpha_range];
}

- Mohamed Jaleel Nazir

Answer 5

试试这个

UIColor(hexString: "#ff33cc")

.

extension UIColor {
  convenience init?(hexString hex: String) {
    var cString: String = hex.trimmingCharacters(in: .whitespacesAndNewlines).uppercased()

    if cString.hasPrefix("#") {
      cString.remove(at: cString.startIndex)
    }

    guard cString.count == 6 else {
      return nil
    }

    var rgbValue: UInt64 = 0
    Scanner(string: cString).scanHexInt64(&rgbValue)

    self.init(
      red: CGFloat((rgbValue & 0xFF0000) >> 16) / 255.0,
      green: CGFloat((rgbValue & 0x00FF00) >> 8) / 255.0,
      blue: CGFloat(rgbValue & 0x0000FF) / 255.0,
      alpha: CGFloat(1.0)
    )
  }
}

- Neenu