OGColorTools.h

//
//  OGColorTools.h
//
//  Created by Jim on 1/25/10.
//  Copyright (c) 2010 Jim Kang/Phalange Software.
//  
//  Permission is hereby granted, free of charge, to any person
//  obtaining a copy of this software and associated documentation
//  files (the "Software"), to deal in the Software without
//  restriction, including without limitation the rights to use,
//  copy, modify, merge, publish, distribute, sublicense, and/or sell
//  copies of the Software, and to permit persons to whom the
//  Software is furnished to do so, subject to the following
//  conditions:
//  
//  The above copyright notice and this permission notice shall be
//  included in all copies or substantial portions of the Software.
//  
//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
//  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
//  OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
//  NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
//  HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
//  WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
//  FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
//  OTHER DEALINGS IN THE SOFTWARE.

#import <Foundation/Foundation.h>
#import "cocos2d.h"

typedef enum 
{
    kRedComp = 0,
    kGreenComp,
    kBlueComp
} ColorComponent;

typedef enum 
{
    kRedToBlue = 0,
    kBlueToRed
} HueShiftDirection;

// This represents the changes that should be applied to a color.
typedef struct _ColorTransform
{
    GLbyte r;
    GLbyte g;
    GLbyte b;
} ColorTransform;

@interface OGColorTools : NSObject 
{
}

+ (GLubyte)addColorComponent:(NSInteger)component to:(NSInteger)otherComponent;
+ (ccColor3B)color:(ccColor3B)clr shiftHue:(CGFloat)percent inDirection:(HueShiftDirection)direction;

@end

OGColorTools.m

//
//  OGColorTools.m
//  lights
//
//  Created by Jim on 1/25/10.
//  Copyright (c) 2010 Jim Kang/Phalange Software.
//  
//  Permission is hereby granted, free of charge, to any person
//  obtaining a copy of this software and associated documentation
//  files (the "Software"), to deal in the Software without
//  restriction, including without limitation the rights to use,
//  copy, modify, merge, publish, distribute, sublicense, and/or sell
//  copies of the Software, and to permit persons to whom the
//  Software is furnished to do so, subject to the following
//  conditions:
//  
//  The above copyright notice and this permission notice shall be
//  included in all copies or substantial portions of the Software.
//  
//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
//  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
//  OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
//  NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
//  HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
//  WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
//  FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
//  OTHER DEALINGS IN THE SOFTWARE.

#import "OGColorTools.h"

// Math functions used by OGColorTools.
@interface OGMath : NSObject 
{
}

+ (NSInteger)lowestOfA:(NSInteger)a b:(NSInteger)b c:(NSInteger)c;
+ (NSInteger)highestOfA:(NSInteger)a b:(NSInteger)b c:(NSInteger)c;
+ (CGFloat)highestFloatOfA:(CGFloat)a b:(CGFloat)b c:(CGFloat)c;
+ (BOOL)pointA:(CGPoint)ptA isWithinDistance:(CGFloat)distance ofPointB:(CGPoint)ptB;

@end

@implementation OGMath

+ (NSInteger)lowestOfA:(NSInteger)a b:(NSInteger)b c:(NSInteger)c
{
    if (a < b)
    {
        if (a < c)
        {
            return a;
        }
        else 
        {
            return c;
        }
    }    
    else 
    { 
        if (b < c)
        {
            return b;
        }
        else 
        {
            return c;
        }
    }
}

+ (NSInteger)highestOfA:(NSInteger)a b:(NSInteger)b c:(NSInteger)c
{
    if (a > b)
    {
        if (a > c)
        {
            return a;
        }
        else 
        {
            return c;
        }
    }    
    else 
    { 
        if (b > c)
        {
            return b;
        }
        else 
        {
            return c;
        }
    }
}


+ (CGFloat)lowestFloatOfA:(CGFloat)a b:(CGFloat)b c:(CGFloat)c
{
    if (a < b)
    {
        if (a < c)
        {
            return a;
        }
        else 
        {
            return c;
        }
    }    
    else 
    { 
        if (b < c)
        {
            return b;
        }
        else 
        {
            return c;
        }
    }
}

+ (CGFloat)highestFloatOfA:(CGFloat)a b:(CGFloat)b c:(CGFloat)c
{
    if (a > b)
    {
        if (a > c)
        {
            return a;
        }
        else 
        {
            return c;
        }
    }    
    else 
    { 
        if (b > c)
        {
            return b;
        }
        else 
        {
            return c;
        }
    }
}

+ (BOOL)pointA:(CGPoint)ptA isWithinDistance:(CGFloat)distance ofPointB:(CGPoint)ptB
{
    CGFloat deltaX = ptA.x - ptB.x;
    CGFloat deltaY = ptA.y - ptB.y;
    CGFloat hypotenuse = sqrt(deltaX * deltaX + deltaY * deltaY);
    return (hypotenuse <= distance);
}

@end

// OGColorTools has the methods that handle hue shifting.
@implementation OGColorTools

+ (GLubyte)addColorComponent:(NSInteger)component to:(NSInteger)otherComponent
{
    if (component + otherComponent > 255)
    {
        return 255;
    }
    if (component + otherComponent < 0)
    {
        return 0;
    }
    return component + otherComponent;
}

// Need this to do some generic programming involving ccColor3B.
+ (GLubyte)valueOfComponent:(ColorComponent)comp ofColor:(ccColor3B)clr
{
    switch (comp) 
    {
        case kRedComp:
            return clr.r;
        case kGreenComp:
            return clr.g;
        case kBlueComp:
        default:
            return clr.b;
    }
}

+ (void)setComponent:(ColorComponent)comp ofColor:(ccColor3B *)clr toValue:(GLubyte)value
{
    switch (comp) 
    {
        case kRedComp:
            clr->r = value;
            break;
        case kGreenComp:
            clr->g = value;
            break;
        case kBlueComp:
            clr->b = value;
            break;
    }
}

+ (ColorComponent)componentToTheRightOf:(ColorComponent)comp 
{
    switch (comp) 
    {
        case kRedComp:
            return kGreenComp;
        case kGreenComp:
            return kBlueComp;
        case kBlueComp:
        default:
            return kRedComp;
    }
}

+ (ColorComponent)componentToTheLeftOf:(ColorComponent)comp 
{
    switch (comp) 
    {
        case kRedComp:
            return kBlueComp;
        case kGreenComp:
            return kRedComp;
        case kBlueComp:
        default:
            return kGreenComp;
    }
}

+ (ccColor3B)color:(ccColor3B)clr 
          shiftHue:(CGFloat)percent 
       inDirection:(HueShiftDirection)direction
{
    // This is the color we'll return, transformed by the end of the method.
    ccColor3B newColor = clr;
    
    // Find the upper and lower limits among the RGB components of this color.
    NSInteger bottom = [OGMath lowestOfA:clr.r b:clr.g c:clr.b];
    NSInteger top = [OGMath highestOfA:clr.r b:clr.g c:clr.b];
    // Use the provided percentage parameter and limis to determine how far 
    // to move a component.
    NSInteger range = top - bottom;
    NSInteger delta = range * percent / 100.0f;
    
    // Iterate over each color component (r, g, and b), and decide whether each 
    // should ascend or descend depending on its value and its neighboring component's 
    // value. Then, apply the ascending or descending change, if there should be one.    
    ColorComponent comp = kRedComp; // Start with red.
    
    for (int i = 0; i < 3; ++i)
    {
        // Get the component value out of the color.
        GLubyte compValue = [OGColorTools valueOfComponent:comp ofColor:clr];
        
        // Get the component that is to the "right" of the current component if we're
        // shifting in the red-to-blue direction. (e.g. If the current component is red, the 
        // component to the "right" will be green.) Otherwise, get the component to the left.
        ColorComponent nextComp = (direction == kRedToBlue) ? 
        [OGColorTools componentToTheRightOf:comp] : [OGColorTools componentToTheLeftOf:comp]; 
        
        // Get the next component's value out of the color.
        GLubyte nextCompValue = [OGColorTools valueOfComponent:nextComp ofColor:clr];
        
        // If this component is not at the the lower limit and the next component is at the 
        // upper limit, this component should descend.
        NSInteger componentDelta = 0;
        if ((compValue > bottom) && (nextCompValue == top))
        {
            componentDelta = -delta;
        }
        // If this component is not at the upper limit and the next component is at the 
        // lower limit, this component should ascend.
        else if ((compValue < top) && (nextCompValue == bottom))
        {
            componentDelta = delta;
        }
        // Otherwise, this component does not need to move.
        if (componentDelta)
        {
            [OGColorTools setComponent:comp 
                               ofColor:&newColor 
                               toValue:[OGColorTools addColorComponent:componentDelta to:compValue]];
        }
        // Move on to the next component.
        comp = nextComp;
    }
    
    return newColor;
}

@end

OGHueShiftExampleLayer.h

//
//  OGHueShiftExampleLayer.h
//  OGColorShift
//
//  Created by Jim on 9/18/10.
//  Copyright Phalange Software 2010. 
//
//
//  Permission is hereby granted, free of charge, to any person
//  obtaining a copy of this software and associated documentation
//  files (the "Software"), to deal in the Software without
//  restriction, including without limitation the rights to use,
//  copy, modify, merge, publish, distribute, sublicense, and/or sell
//  copies of the Software, and to permit persons to whom the
//  Software is furnished to do so, subject to the following
//  conditions:
//  
//  The above copyright notice and this permission notice shall be
//  included in all copies or substantial portions of the Software.
//  
//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
//  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
//  OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
//  NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
//  HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
//  WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
//  FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
//  OTHER DEALINGS IN THE SOFTWARE.



// This is an example scene based on the boilerplate cocos2d HelloWorld 
// scene that demonstrates a simple use of the hue shifting method in 
// OGColorTools. It will load a sprite, set its color, then shift its 
// hue every time the layer is tapped.


// When you import this file, you import all the cocos2d classes
#import "cocos2d.h"

// HelloWorld Layer
@interface OGHueShiftExampleLayer : CCLayer
{
    CCSprite *targetSprite;
}

@property (nonatomic, retain) CCSprite *targetSprite;

// returns a Scene that contains the HelloWorld as the only child
+(id) scene;

@end

OGHueShiftExampleLayer.m

//
//  OGHueShiftExampleLayer.m
//  OGColorShift
//
//  Created by Jim on 9/18/10.
//  Copyright Phalange Software 2010. 
//
//  Permission is hereby granted, free of charge, to any person
//  obtaining a copy of this software and associated documentation
//  files (the "Software"), to deal in the Software without
//  restriction, including without limitation the rights to use,
//  copy, modify, merge, publish, distribute, sublicense, and/or sell
//  copies of the Software, and to permit persons to whom the
//  Software is furnished to do so, subject to the following
//  conditions:
//  
//  The above copyright notice and this permission notice shall be
//  included in all copies or substantial portions of the Software.
//  
//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
//  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
//  OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
//  NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
//  HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
//  WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
//  FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
//  OTHER DEALINGS IN THE SOFTWARE.

// Import the interfaces
#import "OGHueShiftExampleLayer.h"

#import "OGColorTools.h"

// HelloWorld implementation
@implementation OGHueShiftExampleLayer

@synthesize targetSprite;

+(id) scene
{
	// 'scene' is an autorelease object.
	CCScene *scene = [CCScene node];
	
	// 'layer' is an autorelease object.
	OGHueShiftExampleLayer *layer = [OGHueShiftExampleLayer node];
	
	// add layer as a child to scene
	[scene addChild: layer];
	
	// return the scene
	return scene;
}

// on "init" you need to initialize your instance
-(id) init
{
	// always call "super" init
	// Apple recommends to re-assign "self" with the "super" return value
	if( (self=[super init] )) {
		
		// create and initialize a Label
		CCLabel* label = [CCLabel labelWithString:@"Phalange Color Shift example" 
                                         fontName:@"Marker Felt" fontSize:24];
		// ask director the the window size
		CGSize size = [[CCDirector sharedDirector] winSize];        
		label.position = ccp(size.width/2 , size.height/4);
		[self addChild:label];
        
        // Add a sprite whose hue will shift. (Replace this code with code that 
        // loads your own sprite.)
        CCSpriteSheet *spriteManager = [[CCSpriteSheet alloc] 
                                        initWithFile:@"icon.png" 
                                        capacity:1];
        [self addChild:spriteManager];
        self.targetSprite = [CCSprite spriteWithSpriteSheet:spriteManager 
                                                       rect:CGRectMake(0, 0, 57, 57)];
        self.targetSprite.position = ccp(size.width/2 , size.height/2);
        [spriteManager addChild:self.targetSprite];
        
        // Set the sprite's color.
        self.targetSprite.color = ccGREEN;
        
        // Register for touches.
        [[CCTouchDispatcher sharedDispatcher] addTargetedDelegate:self 
                                                         priority:0 
                                                  swallowsTouches:YES];
	
	}
	return self;
}

// on "dealloc" you need to release all your retained objects
- (void) dealloc
{
    [targetSprite release];
    
	// in case you have something to dealloc, do it in this method
	// in this particular example nothing needs to be released.
	// cocos2d will automatically release all the children (Label)
	
	// don't forget to call "super dealloc"
	[super dealloc];
}

#pragma mark TargetedTouchDelegate implementation
- (BOOL)ccTouchBegan:(UITouch *)touch withEvent:(UIEvent *)event
{
    // Shift the hue of the target sprite every time the layer is touched.
    // The swipe was more horizontal than vertical, so do a hue shift.
    self.targetSprite.color = [OGColorTools color:self.targetSprite.color 
                                         shiftHue:100.0f
                                      inDirection:kRedToBlue];    
    return NO;    
}

@end

This is an example of implementing hue shifting in cocos2d as it was explained in this post. OGColorTools contains the code that does the color shifting, and OGHueShiftExampleLayer is a simple example layer that creates a sprite and shifts its color every time the layer is tapped. You will need to provide your own bitmap and load it into the sprite for this to work.

Hi @jimkang, nice observation about hue shifting. But does this support having percentage larger than 100?
I afraid it didn't handle the case yet. But this is really nice and clear implementation.

Thank you very much!