Does your feature request involve difficulty for you to complete a task? Please describe.

Hope Readest could support to adjust the background color of scanned pdfs to what the readers want, just like that in Sumatrapdf [...]

Describe the solution you'd like

To be like the effects in sumatrapdf, even the scanned pdf is a colored page, the background color could be covered but not ruin the color image in the page.

Describe alternatives you've considered

I have no idea.

Additional context

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