Predominant color with VIPS

test1.php

<?php
    require '../vendor/autoload.php';
    use Jcupitt\Vips;
    Vips\Config::concurrencySet(2);
    Vips\Config::CacheSetMax(0);

    //header("Content-type: text/plain");
    //var_dump($_REQUEST);
    
    $mime = "jpeg";
    $ext = ".jpg";
    
    $desired_width = 800;
    
    $f = filter_var($_REQUEST["uri"],FILTER_SANITIZE_STRING);
    
    header("Content-type: image/".$mime);
        //open our huge image and thumbnail it to a buffer
        
    //$image = Vips\Image::newFromFile("produtos/capricorn-4315367.jpg");
    $image = Vips\Image::thumbnail("produtos/capricorn-4315367.jpg", 100);
    
        //calculate aspect ratio for guessing the height of final image
    $aspectRatio = $image->height / $image->width;
 
    /* Keep the width fix at $desired_width, but change the height according to the aspect ratio */
    $desired_height = (int)($aspectRatio * $desired_width);
    
        //quality 1 will pixelate as intended
    $buffer = $image->writeToBuffer($ext,["Q" => 1]); //Karen Stadfelt reference here, Code Geass fans xD
    
        //load image from buffer
    $image2 = Vips\Image::newFromBuffer($buffer, '', ['sequential' => true]);

        //i could get the average, but I want the dominant color
            //https://stackoverflow.com/questions/3468500/detect-overall-average-color-of-the-picture
    
    $block_size = 20;
    $colors = [];
    
    for($x=0; $x<$image2->width; $x += $block_size) {
        for($y=0; $y<$image2->height; $y += $block_size) {
            $rgb = $image2->getpoint($x, $y);
            $red = round(round(($rgb[0] / 0x33)) * 0x33); 
            $green = round(round(($rgb[1] / 0x33)) * 0x33); 
            $blue = round(round(($rgb[2] / 0x33)) * 0x33); 
            $hexRGB = sprintf('%02X%02X%02X', $red, $green, $blue); //line is only usefull when dumping for HTML
            $strRGB = $rgb[0].",".$rgb[1].",".$rgb[2];
            if(array_key_exists($strRGB, $colors)) { 
                $colors[$strRGB]++; 
            } 
            else { 
                $colors[$strRGB] = 1; 
            } 
        }
    }
    arsort($colors);
    //var_dump($colors);
    $rgb = array_key_first($colors);
    $rgb = explode(",",$rgb);
    $colors = []; //free mem space?
    
    
    //create a new image and then fill it with $rgb
        //I find my lack of VIPS knowledge, disturbing
    //var_dump($rgb);
    $im = @imagecreatetruecolor($desired_width, $desired_height) or die("Cannot Initialize new GD image stream");
    $bg = imagecolorallocate($im, (int)$rgb[0] , (int)$rgb[1], (int)$rgb[2]);
    imagefill($im, 0, 0, $bg);
    imagejpeg($im);
    imagedestroy($im);
    //echo $buffer;
     exit;

test2.php

<?php 

    $block_size = 25;
    $colors = [];
        /*
            As instructed in https://github.com/libvips/php-vips/issues/92#issuecomment-549765148, 
            we make a fast thumbnail to 16 and then pixelate with resize
        */
        
    $thumb = Vips\Image::thumbnail($f, 16); 

    $placeholder = $thumb->resize($desired_width / $thumb->width, [
        'scale' => $desired_height / $thumb->height,
        'kernel' => 'nearest'
    ]);

        /* then we create an image from a buffer with sequential access to get pixel information with a block_size, 
        previously measured in Shop or Gimp
        
        */
    $placeholder = Vips\Image::newFromBuffer($placeholder->writeToBuffer($ext), '', ['sequential' => true]);

    for($x=0; $x<$placeholder->width; $x += $block_size) {
        for($y=0; $y<$placeholder->height; $y += $block_size) {
            $rgb = $placeholder->getpoint($x, $y);
            $red = round(round(($rgb[0] / 0x33)) * 0x33); 
            $green = round(round(($rgb[1] / 0x33)) * 0x33); 
            $blue = round(round(($rgb[2] / 0x33)) * 0x33); 
            $hexRGB = "#".sprintf('%02X%02X%02X', $red, $green, $blue); //line is only usefull when dumping for HTML
            //$strRGB = $rgb[0].",".$rgb[1].",".$rgb[2];
            if(array_key_exists($hexRGB, $colors)) { 
                $colors[$hexRGB]++; 
            } 
            else { 
                $colors[$hexRGB] = 1; 
            } 
        }
    }
    arsort($colors);
    $rgb = array_key_first($colors);
    list($alpha, $red, $green, $blue) = parse($rgb); //parse function in https://gist.github.com/kleisauke/a8cdd74c63738eb3add7d9422458aed8

    $thumb = null;
    $placeholder = null;
    $colors = [];
        
        //this part is in https://gist.github.com/kleisauke/a8cdd74c63738eb3add7d9422458aed8
    // Make a 1x1 pixel with the red channel and cast it to provided format.
    $pixel = Vips\Image::black(1, 1)->add($red)->cast(Vips\BandFormat::UCHAR);
    // Extend this 1x1 pixel to match the origin image dimensions.
    $image = $pixel->embed(0, 0, $desired_width, $desired_height, ['extend' => Vips\Extend::COPY]);
    // Ensure that the interpretation of the image is set.
    $image = $image->copy(['interpretation' => Vips\Interpretation::SRGB]);
    // Bandwise join the rest of the channels including the alpha channel.
    $image = $image->bandjoin([
        $green,
        $blue,
        $alpha
    ]);
    $buffer = $image->writeToBuffer($ext);