iOS 獲取十六進制顏色顯示RGB，根據顏色畫圖片

//從十六進制字符串獲取顏色，

//color:支持@“#123456”、 @“0X123456”、 @“123456”三種格式

+ (UIColor *)colorWithHexString:(NSString *)color alpha:(CGFloat)alpha

{

    //刪除字符串中的空格

    NSString *cString = [[colorstringByTrimmingCharactersInSet:[NSCharacterSetwhitespaceAndNewlineCharacterSet]] uppercaseString];

    // String should be 6 or 8 characters

   if ([cString length] <6)

    {

       return [UIColorclearColor];

    }

    // strip 0X if it appears

    //如果是0x開頭的，那麼截取字符串，字符串從索引爲2的位置開始，一直到末尾

   if ([cString hasPrefix:@"0X"])

    {

        cString = [cStringsubstringFromIndex:2];

    }

    //如果是#開頭的，那麼截取字符串，字符串從索引爲1的位置開始，一直到末尾

   if ([cString hasPrefix:@"#"])

    {

        cString = [cStringsubstringFromIndex:1];

    }

   if ([cString length] !=6)

    {

       return [UIColorclearColor];

    }

    

    // 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;

    [[NSScannerscannerWithString:rString] scanHexInt:&r];

    [[NSScannerscannerWithString:gString] scanHexInt:&g];

    [[NSScannerscannerWithString:bString] scanHexInt:&b];

   return [UIColorcolorWithRed:((float)r /255.0f) green:((float)g /255.0f) blue:((float)b /255.0f) alpha:alpha];

}

獲取到顏色以後，畫出這種顏色的圖片

+ (UIImage *)imageWithColor:(UIColor *)color size:(CGSize)size

{

   CGRect rect = CGRectMake(0,0, size.width, size.height);

    UIGraphicsBeginImageContext(rect.size);

    CGContextRef context =UIGraphicsGetCurrentContext();

    CGContextSetFillColorWithColor(context,color.CGColor);

   CGContextFillRect(context, rect);

    UIImage *img =UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

    

   return img;

}