# Image processing pipelines¶

Image processing and tracking pipelines are defined by subclassing the Pipeline class. The pipelines are defined as trees of nodes, starting from the camera image with each node parametrized using lightparam. The image processing nodes are subclasses of ImageToImageNode whereas the terminal nodes are ImageToDataNode

Attributes of pipelines are:

• a tree of processing nodes, along
• (optional) a subclass of the camera window which displays the tracking overlay
• (optional) an extra plotting window class

the nodes can be set as attributes of the class, with names that are arbitrary except for how they are used by the display and plotting classes (see the stytra.experiments.fish_pipelines for examples)

## Processing nodes¶

There are two types of nodes: ImageToImageNode and ImageToDataNode <stytra.tracking.pipelines.ImageToDataNode>

Nodes must have: - A name

• A _process function which contains optional parameters

as keyword arguments, annotated with Params for everything that can be changed from the user interface. The _process function has to output a NodeOutput named tuple (from stytra.tracking.pipeline) which contains a list of diagnostic messages (can be empty), and either an image if the node is a ImageToImageNode or a NamedTuple if the node is a ImageToDataNode

Optionally, if the processing function is stateful (depends on previous inputs), you can define a reset function which resets the state.