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Exercise

Produce a Ruby 2+ program that simulates a basic interactive bitmap editor. Bitmaps are represented as an M x N matrix of pixels with each element representing a colour.

Program input

The input consists of a file containing a sequence of commands, where a command is represented by a single capital letter at the beginning of the line. Parameters of the command are separated by white spaces and they follow the command character.

Pixel co-ordinates are a pair of integers: a column number between 1 and 250, and a row number between 1 and 250. Bitmaps starts at coordinates 1,1. Colours are specified by capital letters.

Commands

There are 6 supported commands:

  • I M N - Create a new M x N image with all pixels coloured white (O).
  • C - Clears the table, setting all pixels to white (O).
  • L X Y C - Colours the pixel (X,Y) with colour C.
  • V X Y1 Y2 C - Draw a vertical segment of colour C in column X between rows Y1 and Y2 (inclusive).
  • H X1 X2 Y C - Draw a horizontal segment of colour C in row Y between columns X1 and X2 (inclusive).
  • S - Show the contents of the current image

Example

To run the application you must supply a command file like so ruby runner.rb commands/template.txt

In the example below, > represents each line of the command file

> I 5 6
> L 2 3 A
> S
OOOOO
OOOOO
OAOOO
OOOOO
OOOOO
OOOOO
> V 2 3 6 W
> H 3 5 2 Z
> S
OOOOO
OOZZZ
OWOOO
OWOOO
OWOOO
OWOOO

When implementing this program focus on quality and best practices. Make sure the program works with odd input and doesn't crash.