Rhombus to rectangle

[digital]

I have an image of a painting which was taken from below the centre line of the painting so, what should be a rectangle, appears as a rhombus. I have previously used either Lightroom 4 or CS6 to correct this but can't for the life of me remember which it was and how to do it. Anyone care to remind me?

 

[ecoleman]

In Lightroom 4 you can use lens correction. Choose manual mode and adjust the sliders until the image is straight.

 

[overbez]

I'd say photshop

edit > transform > distort
or
edit > transform > perspective

pull the corners till you get what you want

 

[digital]

Thanks for the suggestions.

Lightroom lens correction > manual worked but Photoshop edit > transform > distort also did and was much more flexible when it came to images that were out on two axes rather than just one.