Thanks all for the comments and tips.
I'd really like to cut Photoshop from my budget.
I tried the Mold Tool and I found the results quite acceptable.
Here there is a screen-recording with the experiment: https://goo.gl/ULB8S0
Besides the perspective issue, I found the Mold Tool made the bitmap considerable sharper than the original:
IClick image for larger version. 

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The Mold Tool should work for most of my needs.

I would appreciate a further help:
As you can see in the screen-recording, after applying the Mold Tool the clip/crop seems stuck/locked. How to clip/crop the image after Mold Tool adjustments?

Thanks,
Cadu_