颜色常识

#import "ViewController.h"
#import "UIColor+Hex.h"
#define XMGColor(r,g,b) [UIColor colorWithRed:(r) / 256.0 green:(g) / 256.0 blue:(b) / 256.0 alpha:1]
@interface ViewController ()
@property (weak, nonatomic) IBOutlet UILabel *labelView;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    UIColor *color = [UIColor colorWithRed:213 / 255.0 green:213 / 255.0 blue:213 / 255.0 alpha:1];
    _labelView.textColor = [UIColor colorWithHexString:@"eb3535"];
//    _labelView.textColor = XMGColor(255 , 255, 255);
}

/*
    颜色:3种颜色通道 R G B
    颜色表达方式
        24位
        32位
    每一个颜色通道是8位,0~256
    R:213 G:213 B:213
 
    #ffffff
    R:FF => 10进制 255
    G:FF 255
    B:FF 255
 
    #:美工16进制表示形式
    0x:OC16进制表达式
 */

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end

#import <UIKit/UIKit.h>

@interface UIColor (Hex)

// 默认alpha位1
+ (UIColor *)colorWithHexString:(NSString *)color;

//从十六进制字符串获取颜色，
//color:支持@“#123456”、 @“0X123456”、 @“123456”三种格式
+ (UIColor *)colorWithHexString:(NSString *)color alpha:(CGFloat)alpha;

@end

#import "UIColor+Hex.h"

@implementation UIColor (Hex)

+ (UIColor *)colorWithHexString:(NSString *)color alpha:(CGFloat)alpha
{
    //删除字符串中的空格
    NSString *cString = [[color stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]] uppercaseString];
    // String should be 6 or 8 characters
    if ([cString length] < 6)
    {
        return [UIColor clearColor];
    }
    // strip 0X if it appears
    //如果是0x开头的，那么截取字符串，字符串从索引为2的位置开始，一直到末尾
    if ([cString hasPrefix:@"0X"])
    {
        cString = [cString substringFromIndex:2];
    }
    //如果是#开头的，那么截取字符串，字符串从索引为1的位置开始，一直到末尾
    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
    NSString *rString = [cString substringWithRange:range];
    //g
    range.location = 2;
    NSString *gString = [cString substringWithRange:range];
    //b
    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];
}

//默认alpha值为1
+ (UIColor *)colorWithHexString:(NSString *)color
{
    return [self colorWithHexString:color alpha:1.0f];
}

@end