AutoSelectBackground.java

/**
 * Background database for lookups of fittest color to represent.
 */
private static List<Pair<Integer, String>> sBackgrounds = new ArrayList<>();
static {
    // Color Tickets: ------------A-R-G-B-
    sBackgrounds.add(new Pair<>(0xFF040404, "background_01.png"));
    sBackgrounds.add(new Pair<>(0xFF040404, "background_02.png"));
    sBackgrounds.add(new Pair<>(0xFFF2F2F2, "background_03.png"));
    ...
    sBackgrounds.add(new Pair<>(0xFF362810, "background_99.png"));
}

/**
 * Return the fittest background by figuring out the nearest color distance
 * to backgrounds in the database.
 * @param to ARGB color.
 */
public static String getFittestBackgroundPath(int to) {
    int[] rgb = {Color.red(to), Color.green(to), Color.blue(to)};
    float[] lab1 = ColorSpaces.rgbTolab(rgb);
    String result = sBackgrounds.get(0).second;
    float minDist = Float.MAX_VALUE;

    for (Pair<Integer, String> candidate : sBackgrounds) {
        int ticket = candidate.first;
        int[] rgb2 = {Color.red(ticket),
                      Color.green(ticket),
                      Color.blue(ticket)};

        float[] lab2 = ColorSpaces.rgbTolab(rgb2);
        // CIE76 ref : https://en.wikipedia.org/wiki/Color_difference#CIE76
        float dist = Math.abs(lab1[0] - lab2[0]) + Math.abs(lab1[1] - lab2[1]) + Math.abs(lab1[2] - lab2[2]);

        if (dist < minDist) {
            minDist = dist;
            result = candidate.second;
        }
    }
    return result;
}

public static void main() {
  Bitmap bm = getCollageThumbnail();
  // TODO we shouldn't put the color computation on the main thread.
  int color = Palette.from(bm).generate().getLightVibrantColor(Color.WHITE);
  String backgroundFile = BackgroundBundleManager.getFittestBackgroundPath(color);
}