UrlimagePreview: type of image preview jpeg >> png

Is there any reason why preview image renders as jpeg?

Can someone just replace jpeg to png here:

• https://dev.gajim.org/gajim/gajim-plugins/blob/master/url_image_preview/url_image_preview.py#L256
• https://dev.gajim.org/gajim/gajim-plugins/blob/master/url_image_preview/url_image_preview.py#L280

Should I argue why?