How would I fix this warped / skewed photograph?

[King Mustard]

I took a photograph of a book with my mobile phone and, as you can see, the edges look warped.

After searching Google, I have tried using Perspective Warp and the Liquid filter but I can't seem to fix it.

Is anyone able to point me in the right direction, please?

 

[puraidodes]

Try Lens correction in the filter menu and a combination(Perspective Warp, liquify if necessary).
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https://helpx.adobe.com/in/photoshop/using/correcting-image-distortion-noise.html

 

[IamSam]

The distortion is minimal here, so I just used guidelines and Free Transform _____"Cmd/Cntrl + T" > right click - choose warp or choose the warp icon in the tools option bar at the top.

This does not require an overly complicated technique. Fairly easy.

Move these handles to straighten. You may have to move the corner handles as well.

 

[nurgle]

Hi, to distort the image using transform.

1. first pull guides out of the side ruler, and place them just touching the inner closest border of the image that is ten straightest you want.
2 go Command T (iMac) and then use the transform grid at the top to manipulate the orders, as they wont have must effect on the main center of the image.
3. click on the corner handles (one at a time) and drag them towards the middle of the image slightly. remember there may be a slight "Rubber-banding" to other parts of the image.
4. repeat on each corner..
when satisfied with how straight the inner image may be, THEN and only then hit enter, which will force photoshop the fully render the distortion.

note. this is the quick reply. a more complex method id to use small sections, like each edge and doing this "per section", and even then selection smaller and smaller sections, doing this all in turn. over and over till you get it all perfect.

as I said this was just a quick reply to show you how.

Regards, Sandy