iOS - UIColor

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 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 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 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];