There's this method in UIColor in iOS 5:
- (BOOL)getHue:(CGFloat *)hue saturation:(CGFloat *)saturation brightness:(CGFloat *)brightness alpha:(CGFloat *)alpha
But i don't understand how i'm meant to use that in code. Surely i don't need to be stating each of those components if i'm looking to get that out of the UIColor?
CGFloat hue;
CGFloat saturation;
CGFloat brightness;
CGFloat alpha;
[aColor getHue:&hue
saturation:&saturation
brightness:&brightness
alpha:&alpha];
//now the variables hold the values
getHue:saturation:brightness:alpha: returns a bool, determining, if the UIColor could had been converted at all.
Example:
BOOL b = [[UIColor colorWithRed:.23 green:.42 blue:.9 alpha:1.0] getHue:&hue saturation:&saturation brightness:&brightness alpha:&alpha];
NSLog(@"%f %f %f %f %d", hue, saturation, brightness, alpha, b);
will log 0.619403 0.744444 0.900000 1.000000 1, as it is valid
while
BOOL b = [[UIColor colorWithPatternImage:[UIImage imageNamed:@"pattern.png"]] getHue:&hue saturation:&saturation brightness:&brightness alpha:&alpha];
NSLog(@"%f %f %f %f %d", hue, saturation, brightness, alpha, b);
logs 0.000000 0.000000 -1.998918 0.000000 0. The last 0 is the Bool, so this is not valid, and actually brightness can only range from 0.0 to 1.0, but here it holds some random crap.
The code should be something like
CGFloat hue;
CGFloat saturation;
CGFloat brightness;
CGFloat alpha;
if([aColor getHue:&hue saturation:&saturation brightness:&brightness alpha:&alpha]){
//do what ever you want to do if values are valid
} else {
//what needs to be done, if converting failed?
//Some default values? raising an exception? return?
}
Notice that those four parameters are pointers to CGFloats, not just values. This is standard C pass-by-reference. See also the following Stack Overflow questions:
As an example:
CGFloat hue, saturation, brightness, alpha;
[myColor getHue:&hue saturation:&saturation brightness:&brightness alpha:&alpha];
// hue, saturation, brightness, and alpha are now set
