3.2.3. Watershed

Watershed performs a digital image partitioning in different regions, especially when there are image elements that are very close to each other or even connected. The resulting image shows higher pixel intensities of each object in the center areas.

#### 3.2.4. Canny Edge Detector

The Canny algorithm finds and recognizes the contours of objects. It takes five steps during which the grayscale input image undergoes several intermediate transformations. The result obtained represents a binary digital image with only the contours highlighted by strongly marked pixels [53,54].

#### *3.3. Morphological Image Processing*

Morphological image processing alters the structure and geometric shape of an object and applies morphological operations to that portion of the image at each kernel position [55,56]. The morphological operation used in this work is dilation. It acts mainly near the contours of the cells by adding pixels and making it thicker. Expansion reduces and eliminates possible holes inside the cells, often due to binarization defects.
