Get most used colors in the image (like palette)

[maximal]

Thanks to the discussion with @jcupitt in the gist I came up with something like:

/**
 * Скрипт.
 *
 * @author MaximAL
 */

require __DIR__ . '/vendor/autoload.php';
use Jcupitt\Vips\Image;
use Jcupitt\Vips\Access;
use Jcupitt\Vips\Interpretation;


const BINS = 10;
const BIN_SIZE = 256 / BINS;
const PALETTE_MAX_COLORS = 10;

$filename = $argv[1] ?? '2.jpg';


//// VIPS

$image = Image::newFromFile($filename, [
    'access' => Access::SEQUENTIAL,
]);
echo "width×height = {$image->width}×{$image->height}\n";

// Lab?
//$image = $image->colourspace(Interpretation::LAB);
//$image = $image->cast('uchar');

$histogram = $image->hist_find_ndim(['bins' => BINS]);

$max = $histogram->max([
    'out_array' => true,
    'x_array' => true,
    'y_array' => true,
    'size' => PALETTE_MAX_COLORS,
]);

$html = '<style>img { max-height: 25vh; } .color { height: 1.5rem; margin: 0 0 1px 0 }</style>' . PHP_EOL;
$html .= sprintf('<div><img src="%s"></div>', htmlspecialchars($filename)) . PHP_EOL;
$html .= '<h2>VIPS palette top colors</h2>' . PHP_EOL;
$max['out_array'] = array_reverse($max['out_array']);
$max['x_array'] = array_reverse($max['x_array']);
$max['y_array'] = array_reverse($max['y_array']);
foreach ($max['out_array'] as $index => $value) {
    $x = $max['x_array'][$index];
    $y = $max['y_array'][$index];
    $pixel = $histogram->getpoint($x, $y);
    $maxValue = max($pixel);

    echo '#', $index, ' value from `out_array`: ', $value, PHP_EOL;
    echo '#', $index, ' max value from `pixel`: ', $maxValue, PHP_EOL;

    $z = array_search($maxValue, $pixel, true);

    $r = $x * BIN_SIZE + BIN_SIZE / 2;
    $g = $y * BIN_SIZE + BIN_SIZE / 2;
    $b = $z * BIN_SIZE + BIN_SIZE / 2;

    //$patch = $image->newFromImage([$r, $g, $b]);
    //$patch->writeToFile('pal-vips-' . $index . '.png');
    $html .= sprintf(
        '<div class="color" style="background-color: rgba(%d, %d, %d)"></div>' . PHP_EOL,
        $r,
        $g,
        $b
    );
}



//// League\ColorExtractor

$html .= '<h2>League palette top colors</h2>' . PHP_EOL;
$palette = \League\ColorExtractor\Palette::fromFilename($filename);
// Palette’s top colors
//$colors = $palette->getMostUsedColors(PALETTE_MAX_COLORS);
// Extractor’s top colors
$extractor = new \League\ColorExtractor\ColorExtractor($palette);
$colors = $extractor->extract(PALETTE_MAX_COLORS);
foreach ($colors as $color) {
    $rgb = \League\ColorExtractor\Color::fromIntToRgb($color);
    $r = $rgb['r'];
    $g = $rgb['g'];
    $b = $rgb['b'];

    $html .= sprintf(
        '<div class="color" style="background-color: rgba(%d, %d, %d)"></div>' . PHP_EOL,
        $r,
        $g,
        $b
    );
    //$patch = $image->newFromImage([$r, $g, $b]);
    //$patch->writeToFile('pal-league-' . $index . '.png');
}

file_put_contents('out.html', $html);

I use VIPS and League\ColorExtractor here for comparison. Palette is generated to HTML for visual guidance. The result is:

Image from: https://lokeshdhakar.com/projects/color-thief/

Any ideas on how to make results more interesting? Maybe convert to Lab colorspace (I failed to calculate resulting colors from out_array)? The first (most dominant) color is detected almost identically, though.

Also, I noticed that value from out_array is not always the same that the maximum in $pixel array at desired index. Is it okay, or am I doing somenting wrong?

#0 value from `out_array`: 35085
#0 max value from `pixel`: 35085
#1 value from `out_array`: 16213
#1 max value from `pixel`: 16213
#2 value from `out_array`: 8410    // value from `out_array` differs from pixel’s max
#2 max value from `pixel`: 16213   //
#3 value from `out_array`: 5369
#3 max value from `pixel`: 5369
#4 value from `out_array`: 5185
#4 max value from `pixel`: 5185
#5 value from `out_array`: 5055    // value from `out_array` differs from pixel’s max
#5 max value from `pixel`: 35085   //
#6 value from `out_array`: 5027
#6 max value from `pixel`: 5027
#7 value from `out_array`: 4908
#7 max value from `pixel`: 4908
#8 value from `out_array`: 4786
#8 max value from `pixel`: 4786
#9 value from `out_array`: 4706
#9 max value from `pixel`: 4706