Name:
 marker_draw - generate marker bitmaps from marker input list

 Type: Mapper - image filter for Image viewer 

 Author: Ian Curington, AVS/UNIRAS Ltd.

 Language: K&R C
 
 Description:

 This module to takes a marker coordinate specification
 vector XY-pair list on
 an input port from another module, combine this with an
 an input image, and create a composit display image.
 The input image is copied to the output, then marker polygonal
 shapes are scan converted and filled using an edge fill
 algoriythm, with the fill color computed based on
 hue parameters. 
 It is designed and tested with several other marker
 modules, such as marker_pick or marker_select as source
 The vector marker list is defined by structures in the
 "marker.h" header file, defining the structure and usage
 of the field data type for markers.
 Each marker has a compile-time defined shape, but runtime
 attributes of position, size, color, etc.

 Inputs:
   Ref-Image    - Any AVS image, in full color.
   Marker-Input - marker specification list input
   
 Outputs:
   ROI Out - Modified full color image, input plus markers

 Parameters:
   Marker Hue - Hue, part of a color specification for all
                markers except of type "X". Saturation and
                value are prefixed.
   Hilite Hue - Similar control, but for any "X" markers