Color+Interpolation.m

//
//  Color+Interpolation.m
//
//  Created by Leo Natan on 01/10/2016.
//  Copyright © 2016 Leo Natan. All rights reserved.
//

#if __has_include(<UIKit/UIKit.h>) || __has_include(<AppKit/AppKit.h>)

#import "Color+Interpolation.h"

#if __has_include(<UIKit/UIKit.h>)
#define Color UIColor
#else
#define Color NSColor
#endif

#define SWAP(x, y)                                                                                 \
    do {                                                                                           \
        __typeof(x) __ZZZZ__SWAP = x;                                                              \
        x = y;                                                                                     \
        y = __ZZZZ__SWAP;                                                                          \
    } while (0)

// Same value as LNInterpolationBehaviorUseDefault
LNInterpolationBehavior const RNNInterpolationBehaviorUseLABColorSpace =
    @"LNInterpolationBehaviorUseDefault";
LNInterpolationBehavior const RNNInterpolationBehaviorUseRGBColorSpace =
    @"LNInterpolationBehaviorUseRGB";

extern double LNLinearInterpolate(double from, double to, double p);

static NSArray<NSNumber *> *LNRGBComponentsFromColor(Color *color) {
    size_t numberOfComponents = CGColorGetNumberOfComponents(color.CGColor);
    const CGFloat *components = CGColorGetComponents(color.CGColor);

    return numberOfComponents == 2
               ? @[ @(components[0]), @(components[0]), @(components[0]), @(components[1]) ]
               : @[ @(components[0]), @(components[1]), @(components[2]), @(components[3]) ];
}

static Color *LNColorFromRGBComponents(NSArray<NSNumber *> *components) {
    return [Color colorWithRed:components[0].doubleValue
                         green:components[1].doubleValue
                          blue:components[2].doubleValue
                         alpha:components[3].doubleValue];
}

static NSArray<NSNumber *> *LNLabComponentsFromColor(Color *color) {
    NSArray<NSNumber *> *rgbComponents = LNRGBComponentsFromColor(color);
    CGFloat r = rgbComponents[0].doubleValue;
    CGFloat g = rgbComponents[1].doubleValue;
    CGFloat b = rgbComponents[2].doubleValue;

    // RGB -> XYZ
    // http://www.brucelindbloom.com/index.html?Eqn_RGB_to_XYZ.html

    r = (r > 0.04045) ? pow((r + 0.055) / 1.055, 2.4) : (r / 12.92);
    g = (g > 0.04045) ? pow((g + 0.055) / 1.055, 2.4) : (g / 12.92);
    b = (b > 0.04045) ? pow((b + 0.055) / 1.055, 2.4) : (b / 12.92);

    // http://www.brucelindbloom.com/index.html?Eqn_RGB_XYZ_Matrix.html (sRGB ->
    // XYZ)
    CGFloat x = r * 41.24564 + g * 35.75761 + b * 18.04375;
    CGFloat y = r * 21.26729 + g * 71.51522 + b * 07.21750;
    CGFloat z = r * 01.93339 + g * 11.91920 + b * 95.03041;

    // XYZ -> Lab
    // http://www.brucelindbloom.com/index.html?Eqn_XYZ_to_Lab.html

    static const CGFloat eps = 216.0 / 24389.0;
    static const CGFloat k = 24389.0 / 27.0;

    x = x / 100.0; // 95.047;
    y = y / 100.0; // 100.000;
    z = z / 100.0; // 108.883;

    x = x > eps ? pow(x, 1.0 / 3.0) : (k * x + 16.0) / 116.0;
    y = y > eps ? pow(y, 1.0 / 3.0) : (k * y + 16.0) / 116.0;
    z = z > eps ? pow(z, 1.0 / 3.0) : (k * z + 16.0) / 116.0;

    CGFloat l = 116 * y - 16;
    CGFloat a = 500 * (x - y);
    b = 200 * (y - z);

    return @[ @(l), @(a), @(b), rgbComponents[3] ];
}

static Color *LNColorFromLabComponents(NSArray<NSNumber *> *components) {
    CGFloat l = components[0].doubleValue;
    CGFloat a = components[1].doubleValue;
    CGFloat b = components[2].doubleValue;

    // Lab -> XYZ
    // http://www.brucelindbloom.com/index.html?Eqn_Lab_to_XYZ.html

    static const CGFloat eps = 216.0 / 24389.0;
    static const CGFloat k = 24389.0 / 27.0;

    CGFloat y = (l + 16.0) / 116.0;
    CGFloat x = a / 500 + y;
    CGFloat z = y - b / 200;

    x = pow(x, 3.0) > eps ? pow(x, 3.0) : (116 * x - 16) / k;
    y = l > k * eps ? pow((l + 16) / 116, 3.0) : l / k;
    z = pow(z, 3.0) > eps ? pow(z, 3.0) : (116 * z - 16) / k;

    x = x * 1.0; //.95047;
    y = y * 1.0; // 1.00000;
    z = z * 1.0; // 1.08883;

    // XYZ -> RGB

    // http://www.brucelindbloom.com/index.html?Eqn_RGB_XYZ_Matrix.html (XYZ ->
    // sRGB)
    CGFloat r = x * 3.2404542 + y * -1.5371385 + z * -0.4985314;
    CGFloat g = x * -0.9692660 + y * 1.8760108 + z * 0.0415560;
    b = x * 0.0556434 + y * -0.2040259 + z * 1.0572252;

    r = r <= 0.0031308 ? 12.92 * r : 1.055 * pow(r, 1.0 / 2.4) - 0.055;
    g = g <= 0.0031308 ? 12.92 * g : 1.055 * pow(g, 1.0 / 2.4) - 0.055;
    b = b <= 0.0031308 ? 12.92 * b : 1.055 * pow(b, 1.0 / 2.4) - 0.055;

    // return Color
    return LNColorFromRGBComponents(@[ @(r), @(g), @(b), components[3] ]);
}

static inline __attribute__((__always_inline__)) Color *
LNInterpolateColor(Color *fromValue, Color *toValue, CGFloat p, NSArray *(*compConverter)(Color *),
                   Color *(*colorConverter)(NSArray *)) {
    NSArray<NSNumber *> *arrayC1 = compConverter(fromValue);
    NSArray<NSNumber *> *arrayC2 = compConverter(toValue);

    NSMutableArray<NSNumber *> *arrayOutput = [NSMutableArray new];
    [arrayC1
        enumerateObjectsUsingBlock:^(NSNumber *_Nonnull obj, NSUInteger idx, BOOL *_Nonnull stop) {
          arrayOutput[idx] = @(LNLinearInterpolate(obj.doubleValue, arrayC2[idx].doubleValue, p));
        }];

    return colorConverter(arrayOutput);
}

@implementation Color (Interpolation)

- (instancetype)interpolateToValue:(Color *)toValue progress:(double)p {
    return [self interpolateToValue:toValue progress:p behavior:LNInterpolationBehaviorUseDefault];
}

- (instancetype)interpolateToValue:(id)toValue
                          progress:(double)p
                          behavior:(LNInterpolationBehavior)behavior {
    NSParameterAssert([toValue isKindOfClass:[Color class]]);

    if (p <= 0) {
        return self;
    }

    if (p >= 1) {
        return toValue;
    }

    return LNInterpolateColor(
        self, toValue, p,
        behavior == RNNInterpolationBehaviorUseRGBColorSpace ? LNRGBComponentsFromColor
                                                             : LNLabComponentsFromColor,
        behavior == RNNInterpolationBehaviorUseRGBColorSpace ? LNColorFromRGBComponents
                                                             : LNColorFromLabComponents);
}

@end

#endif