calculateProportionalThumbnailSize example

if (empty($maxHeight)) {
            $maxHeight = $maxWidth;
        }

        $newSize = [
            'width' => $maxWidth,
            'height' => $maxHeight,
        ];

        if ($keepProportions) {
            $newSize = $this->calculateProportionalThumbnailSize($originalSize, $maxWidth, $maxHeight);
        }

        $newImage = $this->createNewImage($image, $originalSize, $newSize, $this->getImageExtension($destination));

        if ($this->fixGdImageBlur) {
            $this->fixGdImageBlur($newSize, $newImage);
        }

        $this->saveImage($destination, $newImage, $quality);
        $this->optimizeImage($destination);