Question

I’ve written a camera app which allow users to capture image of paper bills, send to server where it’ll be printed.

Problem:
when I print the image, the background is blackish due to noise in captured image. All I want is a clean white background. I’ve tried Bitmap’s compress method to save the image in JPEG/PNG format on different scales (1-100) but not much helpful. I’ve seen camscanner app doing this fantastically but have no clue how.

Any pointer to achieve this will be helpful.

thanks.

Answer 1

If the issue is some random noise, there are some noise removing filters out there you can use (i.e. median filter or a bilateral filter).

Is the image already binarized (converted to strictly black and white pixels)? You’d want to do the filtering before this.

EDIT(after clarification on dark gray): Since the background is a dark gray I’m guessing the problem is just that it is a low contrast and since it will be a natural image, there will be variation on how bad the contrast is. I suggest using Sauvola binarization for this which will separate out the black and the dark gray to black and white. Here is some detail and example results of Sauvola: http://www.leptonica.com/binarization.html. To run some tests to see which binarization algorithm would be best you can find a library here