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== GraphicalEditorExercise

== Test this solution

ruby graphical_editor_exercise.rb

This is the exercise

== Technical Test
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

= Example
In the example below, > denotes input, => denotes program output.

> I 5 6

> L 2 3 A

> S

=>

OOOOO
OOOOO
OAOOO
OOOOO
OOOOO
OOOOO

> F 3 3 J
> V 2 3 4 W
> H 3 4 2 Z
> S=>
JJJJJ
JJZZJ
JWJJJ
JWJJJ
JJJJJ
JJJJJ