Downscaling with php imagick

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.