Processing how to get the nearest color from a Collection of colors

Question

I have a Collection of Integers of Processing colors (it contains colors of images rescaled to 1x1 to get the "average" color).
I have this thing that must retrieve me the nearest color of the array :

public static int getNearestColor(Collection<Integer> colors, int color) {
    return colors.stream()
        .min(Comparator.comparingInt(i -> Math.abs(i - color)))
        .orElseThrow(() -> new NoSuchElementException("No value present"));
}

But when I do this, it returns me a color that is way far than the input, but the array contains some colors that are nearest than the input, this is my problem that I don't understand ?

Answer 1

The RGB color channels of a color() are encoded in an int. You can extract the red, green and blue component of the color, by red(), green() and blue().
Treat the color channels as a 3 dimensional vector (PVector) and compute the Euclidean distance of 2 color vectors, by dist(). The color with the shortest "distance" is the "nearest" color:

In the following function the arguments c1 and c2 are colors of type int:

float ColorDistance(int c1, int c2) {
    return PVector.dist(
        new PVector(red(c1), green(c1), blue(c1)), 
        new PVector(red(c2), green(c2), blue(c2)));
}

Find the "nearest" color, in a collection of colors, by finding the minimum floating point "distance" (ColorDistance(i, color)).

Answer 2

arrays in java don't have a stream method; perhaps you meant Arrays.stream(colors). IntStream has no way to do a comparison other than on natural order. You can map to the difference (abs(i - color)) first, but now you've deleted the information you were looking for (the original color), so that won't work either. Let's box it. This results in the following code, which is exactly like your code, except this compiles and runs. I'll then also add a test case to make it a self-contained example:

int[] colors = {1,4,5,9,12};
int target = 6;
int a = Arrays.stream(colors).boxed()
    .min(Comparator.comparingInt(i -> Math.abs(i - target)))
    .orElseThrow(() -> new NoSuchElementException());
System.out.println(a);

and, whoa nelly, '5' falls out, which is exactly what you want.

In other words, the intent of your code is fine, if it's not giving the right answer your inputs are not what you thought they are, or something else is wrong that cannot be gleaned from your paste.

May I suggest that if it is at all possible to put the question in a simple, self contained form (as this question clearly was, see the code snippet in this answer), that you do so? Often you'll answer your own questions that way :)

Answer 3

public static int getNearestColor(int[] colors, int color) {
    int minDiff = IntStream.of(colors)
            .map(val -> Math.abs(val - color))
            .min()
            .getAsInt();

    OptionalInt num = IntStream.of(colors)
            .filter(val-> val==(color + minDiff))
            .findFirst();

    if(num.isPresent()){
        return color + minDiff;
    } else {
        return color - minDiff;
    }
  }