react-native-navigation/lib/ios/Utils/UIColor+RNNUtils.m

#import "UIColor+RNNUtils.h"

// Observer 2°, D65 Illuminant
#define REFX_O2_D65 95.047
#define REFY_O2_D65 100.0
#define REFZ_O2_D65 108.883

@implementation UIColor (RNNUtils)

#pragma mark Public
- (NSString *)toHex {
    const CGFloat *components = CGColorGetComponents([self CGColor]);

    CGFloat r = components[0];
    CGFloat g = components[1];
    CGFloat b = components[2];

    return [NSString stringWithFormat:@"#%02lX%02lX%02lX",
                                      lroundf((float) (r * 255)),
                                      lroundf((float) (g * 255)),
                                      lroundf((float) (b * 255))];
}

+ (void)rgbToLabx:(CGFloat)r g:(CGFloat)g b:(CGFloat)b l:(CGFloat *)outL a:(CGFloat *)outA b:(CGFloat *)outB {
    CGFloat x,y,z;
    [UIColor rgbToXYZr:r g:g b:b x:&x y:&y z:&z];
    [UIColor xyzToLabx:x y:y z:z l:outL a:outA b:outB];
}

#pragma mark Private
+ (void)rgbToXYZr:(CGFloat)r g:(CGFloat)g b:(CGFloat)b x:(CGFloat *)outX y:(CGFloat *)outY z:(CGFloat *)outZ {
    if(r > 0.04045) { r = pow(((r + 0.055) / 1.055),2.4); }
    else { r = r / 12.92; }
    if(g > 0.04045) { g = pow(((g + 0.055) / 1.055),2.4); }
    else { g = g / 12.92; }
    if(b > 0.04045) { b = pow(((b + 0.055) / 1.055),2.4); }
    else { b = b / 12.92; }
    
    r *= 100.0;
    g *= 100.0;
    b *= 100.0;
    
    *outX = (r * 0.4124) + (g * 0.3576) + (b * 0.1805);
    *outY = (r * 0.2126) + (g * 0.7152) + (b * 0.0722);
    *outZ = (r * 0.0193) + (g * 0.1192) + (b * 0.9505);
}

+ (void)xyzToLabx:(CGFloat)x y:(CGFloat)y z:(CGFloat)z l:(CGFloat *)outL a:(CGFloat *)outA b:(CGFloat *)outB {
    x /= REFX_O2_D65;
    y /= REFY_O2_D65;
    z /= REFZ_O2_D65;
    
    if(x > 0.008856) { x = pow(x, 1.0/3.0);} else {x = (7.787 * x) +(16.0/116.0);}
    if(y > 0.008856) { y = pow(y, 1.0/3.0);} else {y = (7.787 * y) +(16.0/116.0);}
    if(z > 0.008856) { z = pow(z, 1.0/3.0);} else {z = (7.787 * z) +(16.0/116.0);}
    
    *outL = (116.0 * y) - 16.0;
    *outA = 500.0 * (x - y);
    *outB = 200.0 * (y - z);
}

@end