Pimcore\Model\Asset\Image\Thumbnail::getDimensions PHP Method

    public function getDimensions()
    {
        if (!$this->width || !$this->height) {
            $config = $this->getConfig();
            $asset = $this->getAsset();
            $dimensions = [];
            // first we try to calculate the final dimensions based on the thumbnail configuration
            if ($config) {
                $dimensions = $config->getEstimatedDimensions($asset);
            }
            if (empty($dimensions)) {
                // unable to calculate dimensions -> use fallback
                // generate the thumbnail and get dimensions from the thumbnail file
                $info = @getimagesize($this->getFileSystemPath());
                if ($info) {
                    $dimensions = ["width" => $info[0], "height" => $info[1]];
                }
            }
            $this->width = isset($dimensions["width"]) ? $dimensions["width"] : null;
            $this->height = isset($dimensions["height"]) ? $dimensions["height"] : null;
            // the following is only relevant if using high-res option (retina, ...)
            $this->realHeight = $this->height;
            $this->realWidth = $this->width;
            if ($config && $config->getHighResolution() && $config->getHighResolution() > 1) {
                $this->realWidth = floor($this->width * $config->getHighResolution());
                $this->realHeight = floor($this->height * $config->getHighResolution());
            }
        }
        return ["width" => $this->width, "height" => $this->height];
    }