mmdCalc
Extract the keys of a calculator.

The gray-scale image of the calculator is read.

Image a = mmReadgray("keyb.tif");
mmShow(a);

a

The image edges are enhanced by the gradient operator.

Image b = mmGradm(a, mmSebox());
mmShow(b);

b

The opening top-hat procedure enhances the small objects relatively to its background. In the calculator image, the digits are enhanced.

Image c = mmOpenth(a, mmSebox(5));
mmShow(c);

c

The threshold operator is used to separated the enhanced objects. This procedure is quite robust, since the background was reduced to very low levels with the opening top-hat.

Image d = mmThreshad(c, 150);
mmShow(d);

d

In order to have just one object (i.e., connected component) inside each key, a dilation is applied.

Image e = mmDil(d, mmSebox(3));
mmShow(e);

e

The outside markers are built by taking the watershed (skiz) of the complement of internal markers image.

Image f = mmWatershed(mmNeg(e));
mmShow(f);

f

The markers used are the union of the internal and external markers detected. They are displayed as overlay on the gradient image.

Image g = mmUnion(e, f);
mmShow(b, g);

b, g

The calculator keys are extracted by applying the watershed operator on the gradient image, constrained by the markers detected.

Image h = mmCwatershed(b, g, mmSebox());
mmShow(h);

h

Superposition of the detected contours on the input image.

mmShow(a, h);

a, h