Extracting rgb from UIColor

The code sample you provided should work.

Try this:

UIColor uicolor = [[UIColor greenColor] retain];
CGColorRef color = [uicolor CGColor];


int numComponents = CGColorGetNumberOfComponents(color);


if (numComponents == 4)
{
const CGFloat *components = CGColorGetComponents(color);
CGFloat red = components[0];
CGFloat green = components[1];
CGFloat blue = components[2];
CGFloat alpha = components[3];
}


[uicolor release];

Checkout uicolor-utilities. Seems like a very good library for doing this and many other useful things with UIColor. For example, with this library you could write:

CGFloat red = [myColor red];

Just use memcpy:

CGColorRef tmpColor = [[currentColorView backgroundColor] CGColor];
CGFloat newComponents[4] = {};
memcpy(newComponents, CGColorGetComponents(tmpColor), sizeof(newComponents));
// now newComponents is filled with tmpColor rgba data

In iOS 5 you could use:

UIColor *color = [UIColor orangeColor];
CGFloat red = 0.0, green = 0.0, blue = 0.0, alpha = 0.0;


if ([color respondsToSelector:@selector(getRed:green:blue:alpha:)]) {
[color getRed:&red green:&green blue:&blue alpha:&alpha];
} else {
const CGFloat *components = CGColorGetComponents(color.CGColor);
red = components[0];
green = components[1];
blue = components[2];
alpha = components[3];
}

Here's an all round solution that also takes into account non-RGB colours e.g. [UIColor blackColor]

UIColor *color = [UIColor blackColor];
CGFloat red = 0.0, green = 0.0, blue = 0.0, alpha = 0.0;
// iOS 5
if ([color respondsToSelector:@selector(getRed:green:blue:alpha:)]) {
[color getRed:&red green:&green blue:&blue alpha:&alpha];
} else {
// < iOS 5
const CGFloat *components = CGColorGetComponents(color.CGColor);
red = components[0];
green = components[1];
blue = components[2];
alpha = components[3];
}


// This is a non-RGB color
if(CGColorGetNumberOfComponents(color.CGColor) == 2) {
CGFloat hue;
CGFloat saturation;
CGFloat brightness;
[color getHue:&hue saturation:&saturation brightness:&brightness alpha:&alpha];


}

Thanks for the direction Willster. For any out there who are using grayscale color (created with colorWithWhite:alpha:), the code sample below will let you figure out the white value (the HSV method doesn't work on colors created this way).

CGFloat red = 0.0, green = 0.0, blue = 0.0, alpha = 0.0, white = 0.0;


// This is a non-RGB color
if(CGColorGetNumberOfComponents(self.color.CGColor) == 2) {
[self.color getWhite:&white alpha:&alpha];
}
else {
// iOS 5
if ([self.color respondsToSelector:@selector(getRed:green:blue:alpha:)]) {
[self.color getRed:&red green:&green blue:&blue alpha:&alpha];
} else {
// < iOS 5
const CGFloat *components = CGColorGetComponents(self.color.CGColor);
red = components[0];
green = components[1];
blue = components[2];
alpha = components[3];
}
}