JPEG Artifacts.
Hello everyone !
I tried to upload some images in Konachan but I have some problems with JPEG Artifacts on these. I understand the problem - i've finally found the wiki about that, alleluia ! - but I don't understand how detect the problem.
In the exemple in the Wiki page, you have different images with different artifacts and an original image... And I don't see ANY difference ! It's the same thing. :/
Can you tell me how can I make the difference beetween my correct and uncorrect images before upload ? May I must change JPEG into PNG ?
Thanks for the help.
From what I've seen, all the Brave Girl Ravens CGs are originally in PNG. I don't know the source of them, but your post was the only one from that game that was in JPEG format and that had so much artifacting.

On Konachan, we prefer all our game CGs to be in PNG format. And we don't accept PNG with heavy artifacting.
Artifacting occurs because the jpg compression algorithm majority of information in an image is stored at low frequencies, meaning that there aren't abrupt edges that are important to the image. This works well for photographs but it doesn't work as well for text or anime due to the importance of the crisp edge.

The best way to find artifacting is to find a hard diagonal or curved edge between 2 flat colors and look for slight blocky discoloration in the pixels around the edge. If you want to see extreme jpg artifacting as an example just go on Facebook and see where somebody uploads an image of text. Facebook's compression algorithms are so aggressive that anyone can see the artifacting.

otaku_emmy said:
And we don't accept PNG with heavy artifacting.
In my opinion, PNGs with any artifacting should be rejected as they're clearly not from the original source. PNG is a lossless encoding and should never have artifacting.
Yeah, sorry. That's what I meant. I know we have JPEG only game CGs here (from years ago), but we tend to only accept the PNG now.

If ANYTHING is in PNG but has artifacts it's deleted.