Question

I have a function which receives a UIColor and needs to use it’s RGBA values.
What I did so far was to use CGColorGetComponents but that doesn’t work well for other colorspaces (for example [UIColor blackColor] which is in grayscale).
Using getRed green blue (in iOS 5) also doesn’t work on [UIColor blackColor] (returns false).

Any easy way of doing this?

Answer 1

The following method should work in most cases (except pattern-colors). Add it as a category to UIColor.

- (void)getRGBA:(CGFloat*)buffer {
        CGColorRef clr = [self CGColor];
        NSInteger n = CGColorGetNumberOfComponents(clr);
        const CGFloat *colors = CGColorGetComponents(clr);
        switch (n) {
        case 2:
            for(int i = 0; i<3; ++i){
                buffer[i] = colors[0];
            }
            buffer[3] = CGColorGetAlpha(clr);
            break;
        case 3:
            for(int i = 0; i<3; ++i){
                buffer[i] = colors[i];
            }
            buffer[3] = 1.0;
            break;
        case 4:
            for(int i = 0; i<4; ++i){
                buffer[i] = colors[i];
            }
            break;
        default:
            break;
        }
}