When I change an lower quality image into a higher quality image, I hoped the original image would uploaded as it is, but the uploaded image showing lower quality of the previous lower quality image. The image has been just bigger with low quality. When I upload the same HQ image in another name, the quality of image is similar with the original image. When I move the first uploaded file into another name, the quality of image had got back into original quality. But moving it to the original title, the quality degraded again, not the quality remains. I also tried purge, but the image doesn't renewed.
The problem occurs 'libertygame' wiki(A=File:낚시질.jpg; B=File:낚시질2.jpg; C=File:낚시질1.jpg) and public test wiki(A=File:file test fishing.jpg), but test.wikipedia.org(A=File:file test fishing.jpg) doesn't. So it seems to be miraheze's problem.
- Prepare a small thumbnail image and its original image. (I'm not sure it can be reproduced with totally different images, but it worth to try.)
- Upload the lower quality image. (You're free to name it. I'll call the file's title A.)
- Change the file A into the higher quality image.
- Compare the new file A with original higher quality image you have.
- You'll find that the file A's quality is different with your original file.
- Upload the same higher quality image in another title. (I'll call the file's title B.)
- Compare the file B with original file and file A.
- You'll find that the file B is same with original file you have.
- You'll find that the file B has higher quality than file A.
- Move file A into the different title. (I'll call the new title C.)
- Compare the file C with file A and original file.
- You'll find that the file C have got higher quality than before.
- You'll find that the file C looks same with the original file or file B.
- Move file C into A again.
- Compare the file A with the privious A, file C and original file.
- You'll find that file A have got back into the lower quality of the previous A.
- You'll find that file A looks worse than file C or the original file.