UIColor

Posted 2020-12-27 ch520

• 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

• 1.1 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];

• 1.2 由白色透明度创建

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

• 1.3 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];

• 1.4 由图片创建

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

• 1.5 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];

2、UIColor 与 CIColor 和 CGColor 的相互转换

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

3、由十六进制颜色值创建 RGB 颜色值

• 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];