NAME:       display track 2d

TYPE:       renderer

AUTHOR:     Ian Curington, Stardent Computer Ltd., UK

INPUTS:     field 2D 4-vector byte  (image input)

OUTPUTS:    struct upstream transform

PARAMETERS: toggle: visible cursor (on/off)
            Dither mode

DESCRIPTION:

  Track 2D cursor motion over displayed image.
  This module takes an input image and displays it in an X-window.
  Inputs an image and allows the user create mouse clicks and moves
  in the image window, with event information passed to other
  AVS modules using the "upstream data" concept.
  This module acts similarly to "display image" or
  "display tracker" in that it accepts an input image and
  displays this in an X-window. It also then accepts
  asynchronous mouse events in the window, and passes these
  mouse events ( in an upstream transform structure ) to
  an output port. This allows applications to be built using
  this module to do all the X dependent code, leaving the
  actual operation (such as pan, draw, etc.) to an upstream
  module, with no concern of X events.
  Track 2d will either work silently, or draw an optional
  cursor in the window at each event. Drawing the cursor
  is significantly slower than the silent mode.

  A Dither mode is available, but is only used when the module
  re-maps the image, such as when the input size changes.

  An example network is included.

  Related Modules:
    print_xfrm  (print upstream transform)
    draw_pixel  (draws at x-y into image)
    panel_pan   (pans image in panels with mouse control)