Comparing colors in Objective-C

Question

I am trying to determine if two colors are equivalent using code written in Objective-C.

I use this code snippet to determine if these two colors are equivalent (currently for debugging purposes)

NSLog(@"currentColor is %@", currentColor); NSLog(@"Adjacent Color is %@",[[buttonArray objectAtIndex:1] backgroundColor]); NSLog(@"%i",[[buttonArray objectAtIndex:1] backgroundColor]==currentColor); 

My console shows

 2009-10-20 00:27:10.814 colorGame[13588:207] currentColor is kCGColorSpaceModelRGB 0 0 1 1 2009-10-20 00:27:10.815 colorGame[13588:207] Adjacent Color is kCGColorSpaceModelRGB 0 0 1 1 2009-10-20 00:27:10.815 colorGame[13588:207] 0 

I can post more code if asked (I don't know if this is really necessary). The current color was originally identified as

 UIColor *currentColor; 

if this is any help.

I am sure that I am just doing the comparison incorrectly, and that there is probably a built-in method that can compare colors that I simply don’t know about.

Answer 1

 @implementation UIColor (compare) - (BOOL) isEqualToColor:(UIColor *) otherColor { return CGColorEqualToColor(self.CGColor, otherColor.CGColor); } @end 

Keep in mind that two colors that look the same may or may not return TRUE, since the components are stored as floating, and they may differ by a value less than what the display hardware can resolve.

Also keep in mind that if they are defined in different color spaces, this method will never return TRUE.

Answer 2

objects should be compared using the isEqual: method, not == , which simply compares the pointer address

Answer 3

You check object pointers for equivalence, which will probably never return true. If you want to work with the actual color values, you need to get the CGColor base link.