Downscaling with php imagick - php

Question

I'm having trouble limiting the output of a pdf-to-jpg converter using imagick, but I can't seem to find the right solution for only resizing images larger than 16 megapixel.
https://stackoverflow.com/a/6387086/3405380 has the solution I'm looking for, but I can't find the php equivalent of convert -resize '180000#>' screen.jpg (in my case that would be '16000000#>'). I tried $imagick->resizeImage(Imagick::RESOURCETYPE_AREA, 4000 * 4000);, but that just cuts off the conversion instead of resizing.
public static function storeFilePdfToJpg($file) {
$destinationPath = public_path() . Config::get('my.image_upload_path');
$filename = str_random(10) . '_' . str_replace('.pdf', '', $file->getClientOriginalName()) . '.jpg';
$imagick = new Imagick();
$imagick->setResolution(350,350);
$imagick->readImage($file->getPathName());
$imagick->setImageCompression(imagick::COMPRESSION_JPEG);
$imagick->setImageCompressionQuality(100);
$imagick->resizeImage(Imagick::RESOURCETYPE_AREA, 4000 * 4000);
$imagick->writeImages($destinationPath . '/' . $filename, false);
return Config::get('my.full_image_upload_path') . $filename;
}

Answer 1

The C api for Image Magick doesn't (afaik) expose this functionality, so it isn't possible for the PHP Imagick extension to implement this.
This is pretty easy to implement in PHP:
function openImageWithArea(int $desiredArea, string $filename) : Imagick
{
$image = new Imagick();
$dataRead = $image->pingImage($filename);
if (!$dataRead) {
throw new \Exception("Failed to ping image of filename $filename");
}
$width = $image->getImageWidth();
$height = $image->getImageHeight();
$area = $width * $height;
$ratio = $desiredArea / $area;
$desiredWidth = (int)($ratio * $width);
$desiredHeight = (int)($ratio * $height);
$imagick = new Imagick();
$imagick->setSize($desiredWidth, $desiredHeight);
$imagick->readImage($file);
return $imagick;
}
Should work.