In 90% cases PNG is preferred when we decide, what image should be uploaded and stay, and it's okay.
But not when it's png from
"portfolio.commishes.com ":https://portfolio.commishes.com/ . +
Look at this:
!":https://cdn.discordapp.com/attachments/205721062724337664/746250370686386236/image.png — "source image ":https://portfolio.commishes.com/upload/show/54BN/
Portfolio provides thumbnail, which is in
"_indexed _ PNG ":https://en.wikipedia.org/wiki/Indexed_color — which results in only 256 colors possible. You can clearly see mosaic on zoomed in gradients.
It's possible to extract original quality image from this site (also manually, but it's harder) with
"this script ":/forums/meta/topics/userscript-semi-automated-derpibooru-uploader?post_id=4247301#post_4247301 (see first post for download links). You can do it manually using this link https://portfolio.commishes.com/image/NUMERIC_IMAGE_ID/original/ — like "this ":https://portfolio.commishes.com/image/168311/original/
Keep in mind, that *original can be
+technically + worse* — for exampled image thumb is @1920x1847 PNG @, but original image is @1717x1652 JPEG @ — smaller and jpeg. Thumbs are not only in unsuitable format, but also upscaled — very easily noticeable "here ":https://portfolio.commishes.com/upload/show/6N9A/.
Conclusion: use script to obtain images from this site when possible.