前言

NS_CLASS_AVAILABLE_IOS(2_0) @interface UIColor : NSObject 
    
         @available(iOS 2.0, *)       public class UIColor : NSObject, NSSecureCoding, NSCopying
    

• UIColor、CIColor 和 CGColor 出现在不同的类库里面，其实就是颜色存储方式不同而已，比如 999 可以用 10 进制、2 进制、16 进制等存储。三者之间都是能够方便转换的，特别是很多构造函数。

1、UIColor 的创建

• Objective-C

  • 使用系统定义好的颜色创建

    UIColor *color1 = [UIColor blueColor];    // 附带设置颜色的透明度    UIColor *color1 = [[UIColor blackColor] colorWithAlphaComponent:0.5];

  • 由白色透明度创建

    // alpha：透明度，1 不透明    UIColor *color2 = [UIColor colorWithWhite:1 alpha:0.5];

  • 由三原色创建

    // arc4random()%256/255.0 获取小于等于 1 大于 0 的随机数字    CGFloat red = arc4random()%256/255.0;    CGFloat green = arc4random()%256/255.0;    CGFloat blue = arc4random()%256/255.0;    // Red，green，blue 值的范围是 0 ～ 1，alpha：透明度，1 不透明    UIColor *color3 = [UIColor colorWithRed:red green:green blue:blue alpha:1];

  • 由图片创建

    UIColor *color4 = [UIColor colorWithPatternImage:[UIImage imageNamed:@"13"]];

  • 由 16 进制字符串创建

    NSString *colorString = @"#FF0000";    // 十六进制数字字符串转十进制数字    NSString *s1 = [colorString substringWithRange:NSMakeRange(1, 2)];    unsigned long c1 = strtoul([s1 UTF8String], 0, 16);    NSString *s2 = [colorString substringWithRange:NSMakeRange(3, 2)];    unsigned long c2 = strtoul([s2 UTF8String], 0, 16);    NSString *s3 = [colorString substringWithRange:NSMakeRange(5, 2)];    unsigned long c3 = strtoul([s3 UTF8String], 0, 16);    // Red，green，blue 值的范围是 0 ～ 1，alpha：透明度，1 不透明    UIColor *color5 = [UIColor colorWithRed:c1/255.0 green:c2/255.0 blue:c3/255.0 alpha:1];

• Swift

  • 使用系统定义好的颜色创建

    let color1:UIColor = UIColor.blueColor()    // 附带设置颜色的透明度    let color1:UIColor = UIColor.blackColor().colorWithAlphaComponent(0.5)

  • 由白色透明度创建

    // alpha：透明度，1 不透明    let color2:UIColor = UIColor(white: 1, alpha: 0.5)

  • 由三原色创建

    // arc4random()%256/255.0 获取小于等于 1 大于 0 的随机数字    let red:CGFloat = CGFloat(arc4random()%UInt32(256/255.0))    let green:CGFloat = CGFloat(arc4random()%UInt32(256/255.0))    let blue:CGFloat = CGFloat(arc4random()%UInt32(256/255.0))    // Red，green，blue 值的范围是 0 ～ 1，alpha：透明度，1 不透明    let color3:UIColor = UIColor(red: red, green: green, blue: blue, alpha: 1)

  • 由图片创建

    let color4:UIColor = UIColor(patternImage: UIImage(named: "13")!)

2、UIColor 与 CIColor 和 CGColor 的相互转换

• Objective-C

  // UIColor 转 CGColor    CGColorRef color = [[UIColor greenColor] CGColor];

• Swift

  // UIColor 转 CGColor    let color:CGColorRef = UIColor.greenColor().CGColor

3、由十六进制颜色值创建 RGB 颜色值

• 具体实现代码见 GitHub 源码

• 适用于 0Xc83c23、#c83c23、c83c23 格式的十六进制颜色值。

  /// 由十六进制颜色值创建 RGB 颜色值，带透明度设置    + (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" or "#" if it appears        if ([cString hasPrefix:@"0X"])            cString = [cString substringFromIndex:2];        if ([cString hasPrefix:@"#"])            cString = [cString substringFromIndex:1];        if ([cString length] != 6)            return [UIColor clearColor];        // Separate into r, g, b substrings        NSRange range;        range.location = 0;        range.length = 2;        // r、g、b        NSString *rString = [cString substringWithRange:range];        range.location = 2;        NSString *gString = [cString substringWithRange:range];        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:alpha];    }    /// 由十六进制颜色值创建 RGB 颜色值    + (UIColor *)colorWithHexString:(NSString *)color {        return [UIColor colorWithHexString:color alpha:1.0f];    }

  // 0X 前缀格式    UIColor *color = [UIColor colorWithHexString:@"0Xc83c23"];    UIColor *color = [UIColor colorWithHexString:@"0Xc83c23" alpha:0.5];    // # 前缀格式    UIColor *color = [UIColor colorWithHexString:@"#c83c23"];    UIColor *color = [UIColor colorWithHexString:@"#c83c23" alpha:0.5];    // 无前缀格式    UIColor *color = [UIColor colorWithHexString:@"c83c23"];    UIColor *color = [UIColor colorWithHexString:@"c83c23" alpha:0.5];