Follow along on imgur: http://imgur.com/a/Ddf58 (all the instructions are on the imgur post as well)
1)Generate your receipt
2)Find a picture taken of an actual receipt on google images
3)Save that bitch
4)Open both images in photoshop/gimp
5)Copy and paste the generated receipt onto the real picture
6)Change the opacity of the generated receipt to around 30% so you can see the receipt underneath
7)Go to Edit->Free Transform and rotate the generated receipt to match roughly the same rotation of the real receipt. Do not close the free transform tool yet.
8)Now adjust so the two bottom corners roughly match up with the real reciepts
9)Now go to Edit ->Transform->Warp
10)Adjust all points to line up with those of the real receipt
11)Go up to the top of the page and click the check to apply the transform
12)Now set Opacity back up to 100%
13)Go to Image->Adjustments->Exposure and change the exposure depending on your picture. I change mine to -1.00
14)Go to Image->Adjustments->Brightness/Contrast and change it to whatever looks right. I changed mine to -30
AND DONE!
