Remove a certain pattern from an image in OPENCV

I am trying to write a software for documen开发者_C百科t management. First I Input the blank invoice. then feeds the other invoices with data. Using SIFT detectors i get what type of a invoice it is.

Then I want to remove the interect of the two images. Basically this will keep only the information and remove the common data on the invoice. I want to know is there a proper way to remove areas from the image

there is a concept in imagery called the region of interest. It creates a pointer to a sub-region in the original image, this could help you to read directly at x,y coordinates in the image.

Another possibility would be to make a substraction of the original image. But depending on the quality of the filled form picture, this might lead to other problems.

I was implying the ROI in a sense that you could create a ROI for every place where the form has input data and process only those specific regions

I found a function you might help you, cvAbsDiff, which can subtract an image from another

Here is a link that might help you understanding how to use it
http://blog.damiles.com/?p=67