Ios 确定图像的主颜色和次颜色

我想知道是否有人能帮我弄清楚如何确定UIImage中的主色和副色。我在谷歌上找不到任何非常有用的东西。

恐慌公司的工程师们编写了一种算法，用于进行颜色分析，类似于iTunes11中的颜色分析（以确定良好的主色、次色和细节颜色）。他们发布了一篇关于它的工作原理和代码的解释。

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根据上面的恐慌博客，这里有一个快速的方法（你是什么意思？两种最常用的颜色？太棒了！正是我想要的。ThanksI把它粗略地翻译成iOS Swift，然后使用它，直到它足够快，iOS设备可以毫不延迟地处理它，对吗

-(NSDictionary *)coloursForImage:(UIImage *)image forEdge:(int)edge {

    NSLog(@"start");

    //1. set vars
    float dimension = 20;

    //2. resize image and grab raw data
    //this part pulls the raw data from the image
    CGImageRef imageRef = [image CGImage];
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    unsigned char *rawData = (unsigned char*) calloc(dimension * dimension * 4, sizeof(unsigned char));
    NSUInteger bytesPerPixel = 4;
    NSUInteger bytesPerRow = bytesPerPixel * dimension;
    NSUInteger bitsPerComponent = 8;
    CGContextRef context = CGBitmapContextCreate(rawData, dimension, dimension, bitsPerComponent, bytesPerRow, colorSpace, kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);
    CGColorSpaceRelease(colorSpace);
    CGContextDrawImage(context, CGRectMake(0, 0, dimension, dimension), imageRef);
    CGContextRelease(context);

    //3. create colour array
    NSMutableArray * colours = [NSMutableArray new];
    float x = 0, y = 0; //used to set coordinates
    float eR = 0, eB = 0, eG = 0; //used for mean edge colour
    for (int n = 0; n<(dimension*dimension); n++){

        Colour * c = [Colour new]; //create colour
        int i = (bytesPerRow * y) + x * bytesPerPixel; //pull index
        c.r = rawData[i]; //set red
        c.g = rawData[i + 1]; //set green
        c.b = rawData[i + 2]; //set blue
        [colours addObject:c]; //add colour

        //add to edge if true
        if ((edge == 0 && y == 0) || //top
            (edge == 1 && x == 0) || //left
            (edge == 2 && y == dimension-1) || //bottom
            (edge == 3 && x == dimension-1)){ //right
            eR+=c.r; eG+=c.g; eB+=c.b; //add the colours
        }

        //update pixel coordinate
        x = (x == dimension - 1) ? 0 : x+1;
        y = (x == 0) ? y+1 : y;

    }
    free(rawData);

    //4. calculate edge colour
    Colour * e = [Colour new];
    e.r = eR/dimension;
    e.g = eG/dimension;
    e.b = eB/dimension;

    //5. calculate the frequency of colour
    NSMutableArray * accents = [NSMutableArray new]; //holds valid accents

    float minContrast = 3.1; //play with this value
    while (accents.count < 3) { //minimum number of accents
        for (Colour * a in colours){

            //NSLog(@"contrast value is %f", [self contrastValueFor:a andB:e]);

            //5.1 ignore if it does not contrast with edge
            if ([self contrastValueFor:a andB:e] < minContrast){ continue;}

            //5.2 set distance (frequency)
            for (Colour * b in colours){
                a.d += [self colourDistance:a andB:b];
            }

            //5.3 add colour to accents
            [accents addObject:a];
        }

        minContrast-=0.1f;
    }

    //6. sort colours by the most common
    NSArray * sorted = [[NSArray arrayWithArray:accents] sortedArrayUsingDescriptors:@[[[NSSortDescriptor alloc] initWithKey:@"d" ascending:true]]];

    //6.1 set primary colour (most common)
    Colour * p = sorted[0];

    //7. get most contrasting colour
    float high = 0.0f; //the high
    int index = 0; //the index
    for (int n = 1; n < sorted.count; n++){

        Colour * c = sorted[n];
        float contrast = [self contrastValueFor:c andB:p];
        //float sat = [self saturationValueFor:c andB:p];

        if (contrast > high){
            high = contrast;
            index = n;
        }
    }
    //7.1 set secondary colour (most contrasting)
    Colour * s = sorted[index];

    NSLog(@"er %i eg %i eb %i", e.r, e.g, e.b);
    NSLog(@"pr %i pg %i pb %i", p.r, p.g, p.b);
    NSLog(@"sr %i sg %i sb %i", s.r, s.g, s.b);

    NSMutableDictionary * result = [NSMutableDictionary new];
    [result setValue:[UIColor colorWithRed:e.r/255.0f green:e.g/255.0f blue:e.b/255.0f alpha:1.0f] forKey:@"background"];
    [result setValue:[UIColor colorWithRed:p.r/255.0f green:p.g/255.0f blue:p.b/255.0f alpha:1.0f] forKey:@"primary"];
    [result setValue:[UIColor colorWithRed:s.r/255.0f green:s.g/255.0f blue:s.b/255.0f alpha:1.0f] forKey:@"secondary"];

    NSLog(@"end");
    return result;

}
-(float)contrastValueFor:(Colour *)a andB:(Colour *)b {
    float aL = 0.2126 * a.r + 0.7152 * a.g + 0.0722 * a.b;
    float bL = 0.2126 * b.r + 0.7152 * b.g + 0.0722 * b.b;
    return (aL>bL) ? (aL + 0.05) / (bL + 0.05) : (bL + 0.05) / (aL + 0.05);
}
-(float)saturationValueFor:(Colour *)a andB:(Colour *)b {
    float min = MIN(a.r, MIN(a.g, a.b)); //grab min
    float max = MAX(b.r, MAX(b.g, b.b)); //grab max
    return (max - min)/max;
}
-(int)colourDistance:(Colour *)a andB:(Colour *)b {
    return abs(a.r-b.r)+abs(a.g-b.g)+abs(a.b-b.b);
}

@interface Colour : NSObject
@property int r, g, b, d;
@end