即使图像大小低于最大值kb，图像也会被重新采样

[mattdm (Matthew Miller)]

See this thread:

Auto convert upload to JPG?

I have noticed that some image uploads always convert to jpeg, this creates ugly situations with images with transparent elements and dark/light mode. I couldn’t find a setting for this, can we somehow turn this off? I’ve tried uploading an image in webp, png and it always converts it to jpg, how so?

I assume what you’re seeing is the client-side optimization.