How to use OpenCV to process image so that the text become sharp and clear?

Question

Wanted to achieve something like this: http://www.leptonica.com/binarization.html

While searching for solutions, most of the answers were general instructions such as ad

Answer 1

Instead of using Imgproc.THRESH_BINARY_INV use Imgproc.THRESH_BINARY only as _INV is inverting your image after binarisations and resulted is the said output shown above in your example.

correct code:

Imgproc.adaptiveThreshold(imageMat, imageMat, 255, Imgproc.ADAPTIVE_THRESH_MEAN_C, Imgproc.THRESH_BINARY, 5, 4);

Answer 2

Well, you're almost there. Just try these modifications:

Instead of

    Imgproc.GaussianBlur(imageMat, imageMat, new Size(3, 3), 0);

try:

     cvSmooth(imageMat, imageMat, CV_MEDIAN, new Size(3, 3), 0);

check the syntax, may not exactly match

The link you posted uses thresholding of Otsu, so try this:

 Imgproc.threshold(imageMat, imageMat, 0, 255, Imgproc.THRESH_OTSU);

for thresholding.

Try tweaking the parameters here and there, you should get something pretty close to your desired outcome.