I would like to ask that is it possible to draw borderline - contour - around those cells (pixels) which are neighboring and contains the same value.
An example by hand:
Thanks!
One way is to treat it as an image and to use edgedetect:
img = Import["https://i.sstatic.net/DI4S4.png"];
ImageMultiply[ColorNegate[EdgeDetect[img, 1, 0.1]], img]