Naïve image color sampling

sample.php

<?php 

function get_color_palette($name, $count = 8) {
    $fmap = array(
        'gif'  => 'imagecreatefromgif',
        'png'  => 'imagecreatefrompng',
        'jpg'  => 'imagecreatefromjpg',
        'jpeg' => 'imagecreatefromjpg'
    );
    $path = pathinfo($name);
    $colors = array();
    try {
        list($sw,$sh) = getimagesize($name);
        $ext = strtolower($path['extension']);
        $im = $fmap[$ext]($name);
    } catch (Exception $e) {
        error_log('Error reading image: ' . $name . ' ' . $e->getMessage());
        return $colors;
    }
    // build true color images that are at most 400x300
    $w = min(400,$sw);
    $h = min(300,$sh);
    $tc = imagecreatetruecolor($w,$h);
    $qi = imagecreatetruecolor($w,$h);
    // render a true color representation of the source image
    imagecopyresampled($tc,$im,0,0,0,0,$w,$h,$sw,$sh);
    // dump a sample so we can watch
    imagepng($tc, "/tmp/dump1.png");
    // make a copy
    imagecopy($qi,$tc,0,0,0,0,$w,$h);
    // smooth it
    imagefilter($qi, IMG_FILTER_SMOOTH, 2048);
    // pixelate it so we can loop through less pixels
    imagefilter($qi, IMG_FILTER_PIXELATE, 10, 1);
    // try to "quantize" it by creating a palette that is at least 4 times as big as what we need
    imagetruecolortopalette($qi, false, $count * 8);
    // tune the palette based on the true color image
    imagecolormatch($tc,$qi);
    // dump a copy
    imagepng($qi, "/tmp/dump2.png");

    // do a quick pixel scan
    for($x = 0; $x < $w; $x+=10) {
        for($y = 0; $y < $h; $y+=10) {
            $c = imagecolorsforindex($qi, imagecolorat($qi, $x, $y));
            array_push($colors, sprintf("#%02X%02X%02X", $c['red'], $c['green'], $c['blue']));
        }
    }
    // count unique values
    $dist = array_count_values($colors);
    arsort($dist);
    echo "<pre>";
    var_dump($dist);
    echo "</pre>";
    
    // take the $count most popular values
    $colors = array_merge(array_slice($dist, 0, $count/2), array_slice($dist, count($dist) - ($count), $count));
    $colors = array_keys($colors);
    arsort($colors);
    echo "<pre>";
    var_dump($colors);
    echo "</pre>";
    imagedestroy($tc);
    imagedestroy($im);
    return $colors;
}

$p = get_color_palette("./screenshot.png");



foreach($p as $i) {
    echo '<span style="background-color: '.$i.'">&nbsp;&nbsp;&nbsp;&nbsp;</span>';
}

?>