c++ - Binarize credit card digits before OCR -

i trying binarize credit card digits using opencv ocr reconize them.

so after segmentation stage , cropping,i did these steps:

1.convert tje image grayscale image.

2.histogram equalization.

3.gaussianblur (3,3) kernel gaussianblur(digit,bluredimg,cv::size(3,3),9);

4.threshold(sauvola method).

here of results think noisy , insufficient ocr:

links original images:

http://s22.postimg.org/rqnlgz1od/image.jpg

if have tips enhance binarization quality please share me (code great).

i wouldn't apply "binarize" step @ image. i'd first try remove noise elminating pixels differ neighbours ("salt & pepper filter" because removes black & white spots)