Services/Libravatar.php
protected function processSize($size)
    {
        if ($size === null) {
            return $size;
        }

        $size = (int)$size;
        if ($size <= 0) {
            throw new InvalidArgumentException('Size has to be larger than 0');
        }

        return (int)$size;
    }
protected function processSize($size)
    {
        if ($size === null) {
            return $size;
        }

        $size = (int)$size;
        if ($size <= 0) {
            throw new InvalidArgumentException('Size has to be larger than 0');
        }

        return (int)$size;
    }
Verify and cast the required size of the images.

@param integer $size Size (width and height in pixels) of the image.
NULL for the default width.

@return integer Size

@throws InvalidArgumentException When a size <= 0 is given