/GraphicalEditor

Simple text based "graphical editor". Solution to a little code challenge. 

Graphical editors allow users to edit images in the same way text editors let us
modify documents. Images are represented as an M x N array of pixels with each
pixel given colour.

Produce a program that simulates a simple interactive graphical editor.

Input

The input consists of a line containing a sequence of commands. Each command is
represented by a single capital letter at the start of the line. Arguments to
the command are separated by spaces and follow the command character.

Pixel co-ordinates are represented by a pair of integers: 1) a column number
between 1 and M, and 2) a row number between 1 and N. Where 1 <= M, N <= 250.
The origin sits in the upper-left of the table. Colours are specified by capital
letters.

Commands

The editor supports 7 commands:

1. I M N. Create a new M x N image with all pixels coloured white (O).

2. C. Clears the table, setting all pixels to white (O).

3. L X Y C. Colours the pixel (X,Y) with colour C.

4. V X Y1 Y2 C. Draw a vertical segment of colour C in column X between rows Y1
and Y2(inclusive).

5. H X1 X2 Y C. Draw a horizontal segment of colour C in row Y between columns
X1 and X2 (inclusive).

6. F X Y C. Fill the region R with the colour C. R is defined as: Pixel (X,Y)
belongs to R. Any other pixel which is the same colour as (X,Y) and shares a
common side with any pixel in R also belongs to this region.

7. S. Show the contents of the current image

8. X. Terminate the session