uicolor+lerp.h

//
//  UIColor+lerp.h
//  Lotus
//
//  Created by Andrei on 3/3/13.
//  Copyright (c) 2013 Andrei. All rights reserved.
//

#import <UIKit/UIKit.h>

@interface UIColor (lerp)

- (UIColor *)colorByCombiningWithColor:(UIColor *)toColor power:(float)p;

@end

uicolor+lerp.m

//
//  UIColor+lerp.m
//  Lotus
//
//  Created by Andrei on 3/3/13.
//  Copyright (c) 2013 Andrei. All rights reserved.
//

#import "UIColor+lerp.h"

#define LERP(A, B, X) ((A) * (1.0 - (X)) + (B) * (X))


@implementation UIColor (lerp)

- (CGColorSpaceModel) colorSpaceModel
{
  return CGColorSpaceGetModel(CGColorGetColorSpace(self.CGColor));
}

- (NSString *) colorSpaceString
{
	switch ([self colorSpaceModel])
	{
		case kCGColorSpaceModelUnknown:
			return @"kCGColorSpaceModelUnknown";
		case kCGColorSpaceModelMonochrome:
			return @"kCGColorSpaceModelMonochrome";
		case kCGColorSpaceModelRGB:
			return @"kCGColorSpaceModelRGB";
		case kCGColorSpaceModelCMYK:
			return @"kCGColorSpaceModelCMYK";
		case kCGColorSpaceModelLab:
			return @"kCGColorSpaceModelLab";
		case kCGColorSpaceModelDeviceN:
			return @"kCGColorSpaceModelDeviceN";
		case kCGColorSpaceModelIndexed:
			return @"kCGColorSpaceModelIndexed";
		case kCGColorSpaceModelPattern:
			return @"kCGColorSpaceModelPattern";
		default:
			return @"Not a valid color space";
	}
}

- (BOOL) canProvideRGBComponents
{
	return (([self colorSpaceModel] == kCGColorSpaceModelRGB) ||
			([self colorSpaceModel] == kCGColorSpaceModelMonochrome));
}

- (CGFloat) red
{
	NSAssert (self.canProvideRGBComponents, @"Must be a RGB color to use -red, -green, -blue");
	const CGFloat *c = CGColorGetComponents(self.CGColor);
	return c[0];
}

- (CGFloat) green
{
	NSAssert (self.canProvideRGBComponents, @"Must be a RGB color to use -red, -green, -blue");
	const CGFloat *c = CGColorGetComponents(self.CGColor);
	if ([self colorSpaceModel] == kCGColorSpaceModelMonochrome) return c[0];
	return c[1];
}

- (CGFloat) blue
{
	NSAssert (self.canProvideRGBComponents, @"Must be a RGB color to use -red, -green, -blue");
	const CGFloat *c = CGColorGetComponents(self.CGColor);
	if ([self colorSpaceModel] == kCGColorSpaceModelMonochrome) return c[0];
	return c[2];
}

- (CGFloat) alpha
{
	const CGFloat *c = CGColorGetComponents(self.CGColor);
	return c[CGColorGetNumberOfComponents(self.CGColor)-1];
}

- (UIColor *)colorByCombiningWithColor:(UIColor *)toColor power:(float)p {
    return [UIColor colorWithRed:LERP(self.red,     toColor.red,    p)
                           green:LERP(self.green,   toColor.green,  p)
                            blue:LERP(self.blue,    toColor.blue,   p)
                           alpha:LERP(self.alpha,   toColor.alpha,  p)];
}

@end