颜色转换

http://www.cocoachina.com/iphonedev/sdk/2011/0622/2969.html

photoshop 色彩模式 ：RGB模式，CMYK模式，等

UIColor 、CIColor和CGColor  不同类库里面的颜色存储方式

目标：UIColor

来源：html 颜色值 16进制，比如：#FF9900、0XFF9900 等颜色字符串。  

#F6F6F6 为一个 16 进制表示的RBG颜色，所以，需要先转换成 10进制，其中 F6 - 240，F6 -  240 ，F6 - 240之后，

#define DEFAULT_VOID_COLOR [UIColor clearColor]+ (UIColor *) colorWithHexString: (NSString *) stringToConvert    {     NSString *cString = [[stringToConvert stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]] uppercaseString];          // String should be 6 or 8 characters     if ([cString length] < 6) return DEFAULT_VOID_COLOR;          // strip 0X if it appears     if ([cString hasPrefix:@"0X"]) cString = [cString substringFromIndex:2];     if ([cString hasPrefix:@"#"]) cString = [cString substringFromIndex:1];     if ([cString length] != 6) return DEFAULT_VOID_COLOR;     // Separate into r, g, b substrings     NSRange range;     range.location = 0;     range.length = 2;     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:1.0f];    }

目标：UIColor
来源：RGB
[UIColor colorWithRed:((float) r / 255.0f) green:((float) g / 255.0f) blue:((float) b / 255.0f) alpha:1.0f];

UIColor:

UIColor blackColor
UIColor darkGrayColor
UIColor lightGrayColor
UIColor whiteColor
UIColor grayColor
UIColor redColor
UIColor greenColor
UIColor blueColor
UIColor cyanColor
UIColor yellowColor
UIColor magentaColor
UIColor orangeColor
UIColor purpleColor
UIColor brownColor
UIColor clearColor
UIColor lightTextColor
UIColor darkTextColor
UIColor groupTableViewBackgroundColor
UIColor viewFlipsideBackgroundColor
UIColor scrollViewTexturedBackgroundColor
UIColor underPageBackgroundColor