CSC151.01 2006S, Class 36: Drawing with Script-Fu

Admin:
* EC for Friday's DragStravagaza.
* EC for Saturday's Football Game.
* The inappropriate question issue has been resolved.
* Continuing in CS?  (152 vs. 105)
* The distractions of the GIMP.
* Thursday, 9 Nov, noon: Thursday extra (with pizza!)
* Questions on the exam?
  Q Do we have to document kernel and husk?
  A If the kernel is local, you need not document it.
  Q How many P's?
  A The basic six P's.
  Q Will we get extra credit for using more than six P's?
  A It depends on (a) the correctness of the extra documentation and
    (b) my mood.

Overview:
* Representing drawings.
* Transforming drawings.
* Lab.

Thesis: Um?  I don't know.  Um.
Thesis: We can represent many drawings as a sequence of dots that
  we connect.
Issues:
* Why?
  * Goes beyond lines
  * Clever programmers might be able to turn sequences of dots into curves
  * Easy to modify pictures 
    * Scale
    * Vary points slightly for different images
    * Move
    * Rotate
    * Draw in different colors and brushes
* How?
  * Represent points as dotted pairs.
  * But hide that representation from the client
    point, xcoord, ycoord, point?
  * Represent parts of a drawing as sequences of points
  * Represent drawings as sequences of sequences of points
  * Draw one sequence of points with
    (connect-the-dots image points)
  * Draw a drawing with
    (draw image drawing)
  * (htrans-point amt point) also htrans-points also htrans
  * (vtrans-point amt point)
  * (scale-point amt point)
  * (hscale-point amt point)
  * (vscale-point amt point)
  * (vary amt point)