Simple interactive graphical editor

A Scala program that simulates a simple interactive graphical editor. This is a solution to a technical test outlined below.

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.

> I56
> L23A
> S

=>
OOOOO
OOOOO
OAOOO
OOOOO
OOOOO
OOOOO

> F33J 
> V234W 
> H342Z 
> S

=>
JJJJJ
JJZZJ
JWJJJ
JWJJJ
JJJJJ
JJJJJ

License

MIT