This network zooms and smoothes an image from disk, displaying and storing the result:
(The arrows denote dependencies, not the flow of data.)
Every node supports the
getTile method. For sources, this
simply returns a rectangular portion of the image. For operators, this
causes them to read a portion of their input image, process it, and output
the corresponding portion of the output image. The input to an operator
could be another operator; this is transparent because of the
Image operators include:
ImageVision speeds requests by caching the output of each node. Pieces of the requested region which are already in the cache will not be recomputed. This is especially useful for fan-out. When the parameters of an operator node change, the nodes which follow in the network must have their caches invalidated.
Nodes can compute in parallel. For example, a so-called eager node can fill its cache with data that it expects will be needed later. An operator can also break a request into smaller chunks: it requests the next few chunks while processing the current chunk.