如何在objective-c中将RGB十六进制字符串转换为UIColor？

Question

我有来自 url 数据的颜色值是这样的，“#ff33cc”。如何将此值转换为 UIColor？我正在尝试使用以下代码行。我没有正确获得 baseColor1 的值。看来我应该把那磅炭去掉。还有其他方法吗？

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

Answer 1

您已经接近了，但 colorWithRed:green:blue:alpha: 预计值范围为 0.0 到 1.0，因此您需要将位右移并除以 255.0f：

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

EDIT - NSScanner 的 scanHexInt 也会跳过十六进制字符串前面的 0x，但我认为它不会跳过十六进制字符串前面的 # 字符。您可以添加此行来处理：

[scanner2 setCharactersToBeSkipped:[NSCharacterSet symbolCharacterSet]]; 

Answer 2

我添加了一个字符串替换，因此它接受带有或不带有 # 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];
}

Answer 3

我制作了一个适用于以下情况的函数：- 1) 有或没有# 2) 3 和 6 字符长值 #000 以及 #000000 3）如果多余的数字超过六个，它会忽略多余的数字

//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];
}}

Answer 4

斯威夫特

很有用

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

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];
}