Introduction

The following text will describe the process of building a plugin for the Visual Surveillance System (VSL).

It is all in the interface

In order to build a plugin for VSL there is a need to implement one interface called ISurveillanceSystem. This interface gives all the information needed in order to configure and use the plugin. When the application loads a plugin from a dll it looks for this interface.

Configuration

A configuration for a plugin is defined in 4 levels: before runtime configuration, runtime configuration, runtime information and graphical display.

Before runtime configuration

Before runtime configuration controls how the plugin will be initialized and is defined by two properties:

1. IsConfigurable - If this property returns true it means that the user can configure the surveillance system by clicking "Configure" button on the Configure form.
2. ConfigurationForm - If the above property returns true then you need to implement this property and return a form that allows the user to configure the plugin. Pay attention that the form must inherit from ConfigurationForm.

Runtime configuration

Unlike the previous properties the following 3 properties define how to configure the plugin during its runtime. If enabled the user can click "Configure Surveillance System" on the main form and a configuration form will be displayed.

1. IsRuntimeConfigurable - If this property returns true it means that the user can configure the surveillance system by clicking "Configure Surveillance System" on the main form.
2. RuntimeConfigurationForm - If the above property returns true you need to implement this property and return a form that allows the user to configure the plugin. Pay attention that the form must inherit from ConfigurationForm.
3. SetRuntimeConfiguration - Allows you to set the configuration gathered in the runtime configuration form.

Runtime information

Sometimes you want to give the user the ability to view the inner mechanism of the surveillance system, the following two properties give this ability:

1. HasRuntimeInformation - If this property returns true it means that the user can view runtime information by clicking "Show Runtime Information" on the main form.
2. RuntimeInformation - If the above property returns true you need to implement this property and return a form that allows the user to view runtime information.

Graphical display

Sometimes you do not want to display anything on the screen you want your plugin just to work behind the scenes on the other hand you can change the way the plugin displays its results on screen. You can configure this behavior by using the following two properties:

1. HasGraphicalOutput - If true the output of the surveillance system will be displayed on screen.
2. GraphicalOutput - Returns a delegate that changes the image that will be displayed on screen.

The algorithm

A surveillance system is not complete without an algorithm that does the real surveillance. GetImageProcess returns an IImageProcess interface that defines the algorithm. In order to fully understand how such an algorithm might work you can read an article on the subject published in CodeProject.