Everything the Framework does is determined by a network. A network is a collection of modules that are connected to each other. A module is a program that can be run from the Framework. A module is usually designed to perform a specific step in the process of image preprocessing. The connections between the modules determine how the output of one module is used as input of another module.
You can use the Framework to create, change, load, save and run networks.
In this test, you will create a network that can find the contour of the head
in a picture of a face. The program that actually performs this task, is a
program written in the programming language C by Jan Hejda and Josef
Šivic. This program is converted into a module called ``Find head
contour''. Its input is a grey-scale image. It is stored as a
two-dimensional array of bytes. Each byte contains the grey level of one
pixel. In the Framework, this format is called Grey data. Grey data
cannot be loaded from a file. It must be created by a module that generates
Grey data as output. For this test, the module called ``Color to Grey'' will
be used. It converts Color data to Grey data. The Color data is a data
format used to store color images. Color data also can't be loaded from a
file. It must be created by a module that generates Color data as output.
For this test, the module called ``Image to Color'' will be used. This module
converts ImageData to Color data. The Framework can read ImageData from
common graphics formats like GIF, JPEG, Targa, PPM and
bitmap
. Since ImageData can be loaded from a file, the module
``ImageData to Color'' will the module in the network where the execution of
the network starts.
So, the process of finding the contour of a head consists of three steps. The first two steps are simple preprocessing: first converting a image into Color data using module ``ImageData to Color'', then converting the Color data into Grey data using module ``Color to Grey''. The third step is clearly the most important: it locates the head in the Grey data. For each step, there must be a module in the network.