Professional WordPress Plugins and Services. wpDiscuz, WooDiscuz, Advanced Post Pagination
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Settings:
I do not know what is causing this, but the resolution of the attached image is reduced.
URL of uploaded image: 
URL of the displayed image: 
If you open the image in a new tab and zoom in, you will see that the resolution is reduced.
How can I upload an image without reducing its resolution?
Sorry for the late reply.
It worked fine. Thank you very much!