Automated

A resident function in ImageJ, located in the menu as [Process > Binary > Voronoi].

Quote from the ImageJ reference page:

Splits the image by lines of points having equal distance to the borders of the two nearest particles. Thus, the Voronoi cell of each particle includes all points that are nearer to this particle than any other particle. When particles are single points, this process is a Voronoi tessellation (also known as Dirichlet tessellation). The output type (Overwrite, 8-bit, 16-bit or 32-bit) of this command can be set in the [Process > Binary > Options...] dialog box. In the output, the value inside the Voronoi cells is zero; the pixel values of the dividing lines between the cells are equal to the distance between the two nearest particles. This is similar to a medial axis transform of the background, but there are no lines in inner holes of particles.

An object detection function in ImageJ. [Analyze > Analyze Particles...]. It could simply be used for counting number of cells, but could also do more complex stuffs. ## Jython Snippet Here is a snippet of how to use Particle Analysis in Jython script.

ImageJ macro for the morphometry of neurites. > NeurphologyJ; it is capable of automatically quantifying neuronal morphology such as soma number and size, neurite length, neurite ending points and attachment points. NeurphologyJ is implemented as a plugin to ImageJ, an open-source Java-based image-processing and analysis platform.

Estimate the frequency of hepatitis C virus infected cells based on the intensity of viral antigen associated immunofluorescence. 

The core is an ImageJ Macro, so it's easy to modify for one's own needs (Link to the code). 

XuvTools (pronounced “ex-you-vee-tools”) is a fully automated 3D stitching software for biomedical image data, typically confocal microscopy images. XuvTools runs on Microsoft Windows XP and Vista, Linux and Apple Mac computers. It supports 32 and 64bit operating systems (with 64bit highly preferred). XuvTools is free and open source software (see Licensing), so you can start using it immediately. Go to Downloads and give it a try. The goal of XuvTools is to provide tools, that combine multiple microscopic recordings to obtain a larger field of view (“stitching”) and a higher dynamic range (“HDR” recombination), or better resolution (multi view reconstruction), and to make these tools publicly available.