General scaling
Describe the transformation represented by matrix S = {{2,0},{0,1}}.
Find scaling axes, i.e. fixed directions.
General scaling has a separate scale factor for each axis direction. Non-uniform scaling is obtained when at least one of the scaling factors is different from the others; a special case is directional scaling or stretching (in one direction). Non-uniform scaling changes the shape of the object; e.g. a square may change into a rectangle, or into a parallelogram if the sides of the square are not parallel to the scaling axes.
