前言

    NS_CLASS_AVAILABLE_IOS(2_0) @interface UIColor : NSObject <NSSecureCoding, NSCopying>@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 CGColorCGColorRef color = [[UIColor greenColor] CGColor];

• Swift

      // UIColor 转 CGColorlet 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 QExtension

• 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 charactersif ([cString length] < 6) {return [UIColor clearColor];}// strip "0X" or "#" if it appearsif ([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 substringsNSRange range;range.location = 0;range.length = 2;// r、g、bNSString *rString = [cString substringWithRange:range];range.location = 2;NSString *gString = [cString substringWithRange:range];range.location = 4;NSString *bString = [cString substringWithRange:range];// Scan valuesunsigned 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];