Decrease image size
        :param resource:
        :return:

def _decrease(self, resource):
        """
        Decrease image size
        :param resource:
        :return:
        """
        original_width, original_height = resource.size

        if original_width > self.value and original_height > self.value:
            target_width = original_width - self.value
            target_height = original_height - self.value

            resource = resource.resize((target_width, target_height), Image.ANTIALIAS)

            return resource
        else:
            raise ValueError('Image dimensions less than or equal to filter value.')