我如何从十六进制字符串格式创建一个UIColor,如#00FF00?
当前回答
为UIColor创建优雅的扩展:
extension UIColor {
convenience init(string: String) {
var uppercasedString = string.uppercased()
uppercasedString.remove(at: string.startIndex)
var rgbValue: UInt32 = 0
Scanner(string: uppercasedString).scanHexInt32(&rgbValue)
let red = CGFloat((rgbValue & 0xFF0000) >> 16) / 255.0
let green = CGFloat((rgbValue & 0x00FF00) >> 8) / 255.0
let blue = CGFloat(rgbValue & 0x0000FF) / 255.0
self.init(red: red, green: green, blue: blue, alpha: 1)
}
}
创建红色:
let red = UIColor(string: "#ff0000")
其他回答
你可以使用这个库
https://github.com/burhanuddin353/TFTColor
斯威夫特
UIColor.colorWithRGB(hexString: "FF34AE" alpha: 1.0)
objective - c
[UIColor colorWithRGBHexString:@"FF34AE" alpha:1.0f]
另一个实现允许字符串“FFF”或“FFFFFF”,并使用alpha:
+ (UIColor *) colorFromHexString:(NSString *)hexString alpha: (CGFloat)alpha{
NSString *cleanString = [hexString stringByReplacingOccurrencesOfString:@"#" withString:@""];
if([cleanString length] == 3) {
cleanString = [NSString stringWithFormat:@"%@%@%@%@%@%@",
[cleanString substringWithRange:NSMakeRange(0, 1)],[cleanString substringWithRange:NSMakeRange(0, 1)],
[cleanString substringWithRange:NSMakeRange(1, 1)],[cleanString substringWithRange:NSMakeRange(1, 1)],
[cleanString substringWithRange:NSMakeRange(2, 1)],[cleanString substringWithRange:NSMakeRange(2, 1)]];
}
if([cleanString length] == 6) {
cleanString = [cleanString stringByAppendingString:@"ff"];
}
unsigned int baseValue;
[[NSScanner scannerWithString:cleanString] scanHexInt:&baseValue];
float red = ((baseValue >> 24) & 0xFF)/255.0f;
float green = ((baseValue >> 16) & 0xFF)/255.0f;
float blue = ((baseValue >> 8) & 0xFF)/255.0f;
return [UIColor colorWithRed:red green:green blue:blue alpha:alpha];
}
据我所知,没有从十六进制字符串到UIColor(或CGColor)的内置转换。但是,您可以很容易地为此目的编写几个函数—例如,参见iphone开发访问uicolor组件
我已经找到了一个与Android使用的十六进制格式字符串100%兼容的解决方案,我发现这在进行跨平台移动开发时非常有用。它让我在两个平台上都使用一种颜色。您可以在没有归属的情况下随意重用,如果您愿意,也可以在Apache许可下重用。
#import "UIColor+HexString.h"
@interface UIColor(HexString)
+ (UIColor *) colorWithHexString: (NSString *) hexString;
+ (CGFloat) colorComponentFrom: (NSString *) string start: (NSUInteger) start length: (NSUInteger) length;
@end
@implementation UIColor(HexString)
+ (UIColor *) colorWithHexString: (NSString *) hexString {
NSString *colorString = [[hexString stringByReplacingOccurrencesOfString: @"#" withString: @""] uppercaseString];
CGFloat alpha, red, blue, green;
switch ([colorString length]) {
case 3: // #RGB
alpha = 1.0f;
red = [self colorComponentFrom: colorString start: 0 length: 1];
green = [self colorComponentFrom: colorString start: 1 length: 1];
blue = [self colorComponentFrom: colorString start: 2 length: 1];
break;
case 4: // #ARGB
alpha = [self colorComponentFrom: colorString start: 0 length: 1];
red = [self colorComponentFrom: colorString start: 1 length: 1];
green = [self colorComponentFrom: colorString start: 2 length: 1];
blue = [self colorComponentFrom: colorString start: 3 length: 1];
break;
case 6: // #RRGGBB
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];
break;
case 8: // #AARRGGBB
alpha = [self colorComponentFrom: colorString start: 0 length: 2];
red = [self colorComponentFrom: colorString start: 2 length: 2];
green = [self colorComponentFrom: colorString start: 4 length: 2];
blue = [self colorComponentFrom: colorString start: 6 length: 2];
break;
default:
[NSException raise:@"Invalid color value" format: @"Color value %@ is invalid. It should be a hex value of the form #RBG, #ARGB, #RRGGBB, or #AARRGGBB", hexString];
break;
}
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;
}
@end
迅速:
extension UIColor {
convenience init?(hexString: String?) {
let input: String! = (hexString ?? "")
.replacingOccurrences(of: "#", with: "")
.uppercased()
var alpha: CGFloat = 1.0
var red: CGFloat = 0
var blue: CGFloat = 0
var green: CGFloat = 0
switch (input.count) {
case 3 /* #RGB */:
red = Self.colorComponent(from: input, start: 0, length: 1)
green = Self.colorComponent(from: input, start: 1, length: 1)
blue = Self.colorComponent(from: input, start: 2, length: 1)
break
case 4 /* #ARGB */:
alpha = Self.colorComponent(from: input, start: 0, length: 1)
red = Self.colorComponent(from: input, start: 1, length: 1)
green = Self.colorComponent(from: input, start: 2, length: 1)
blue = Self.colorComponent(from: input, start: 3, length: 1)
break
case 6 /* #RRGGBB */:
red = Self.colorComponent(from: input, start: 0, length: 2)
green = Self.colorComponent(from: input, start: 2, length: 2)
blue = Self.colorComponent(from: input, start: 4, length: 2)
break
case 8 /* #AARRGGBB */:
alpha = Self.colorComponent(from: input, start: 0, length: 2)
red = Self.colorComponent(from: input, start: 2, length: 2)
green = Self.colorComponent(from: input, start: 4, length: 2)
blue = Self.colorComponent(from: input, start: 6, length: 2)
break
default:
NSException.raise(NSExceptionName("Invalid color value"), format: "Color value \"%@\" is invalid. It should be a hex value of the form #RBG, #ARGB, #RRGGBB, or #AARRGGBB", arguments:getVaList([hexString ?? ""]))
}
self.init(red: red, green: green, blue: blue, alpha: alpha)
}
static func colorComponent(from string: String!, start: Int, length: Int) -> CGFloat {
let substring = (string as NSString)
.substring(with: NSRange(location: start, length: length))
let fullHex = length == 2 ? substring : "\(substring)\(substring)"
var hexComponent: UInt64 = 0
Scanner(string: fullHex)
.scanHexInt64(&hexComponent)
return CGFloat(Double(hexComponent) / 255.0)
}
}
你可以做这样的扩展
extension UIColor {
convenience init(hex: UInt, alpha: CGFloat = 1) {
self.init(
red: CGFloat((hex & 0xFF0000) >> 16) / 255.0,
green: CGFloat((hex & 0x00FF00) >> 8) / 255.0,
blue: CGFloat(hex & 0x0000FF) / 255.0,
alpha: alpha
)
}
}
像这样用在任何地方
let color1 = UIColor(hex: 0xffffff)
let color2 = UIColor(hex: 0xffffff, alpha: 0.2)
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