15110 SUMMER SESSION ONE - 2013

Lab 11 - Wednesday, June 19

CA Demonstration

Write a Ruby function that creates a window of size 320 X 320 and draws an 8 X 8 grid of squares that are 40 X 40 each, each colored a random color of red, green or blue.

Deliverables

  1. demo.rb (CA demo)
  2. random_boxes.rb
  3. checker_board.rb
  4. data_display.rb
  5. random_rectangles.rb (open ended)

RubyLabs Canvas

In order to draw in Ruby, you need to create a Canvas which you can do as follows:

Canvas.init(width, height, title)

where you replace width, height and title with appropriate values. The width and height are expressed in pixels and the title is a string (with no spaces).

In a window, the coordinate system is upside down from what you might expect mathematically. The x coordinates increase from left to right, but the y coordinates increase from top to bottom. So the origin (0,0) is in the top left corner of the window.

To draw a rectangle using the Canvas, you need to create a new Rectangle and supply the coordinates of the top left and bottom right corners along with additional optional parameters:

Canvas::Rectangle.new(topleft_x, topleft_y, bottomright_x, bottomright_y, optional parameter(s))

For example, to create a red square with a blue border that has a top left coordinate of (100,100) and bottom right coordinate of (110, 110), you would execute:

Canvas::Rectangle.new(100, 100, 110, 110, :fill => "red", :outline => "blue")

Activities

  1. Write a Ruby function, random_boxes(), that creates a window of size 320 X 320 and draws an 40 X 40 grid of squares that are 8 X 8 each, each colored a random color from black, white, yellow, cyan, and magenta.

    Note: your results may vary since we're using a random number generator. You may, however, be able to reproduce the result above if you call srand(15110) immediately before calling your function.

  2. Write a function, checker_board(). that displays an 8 X 8 checker board using red and black squares in a window of size 400 X 400. Use loops to simplify the function. There is a pattern here so that you only need one call to the Canvas::Rectangle.new function. For this problem, you can leave out the optional parameter :outline when you create the squares.

  3. Write a function data_display(matrix) that takes a 4 X 4 array (matrix) as its parameter and displays a 4 X 4 grid of rectangles in a window of size 320 (width) X 240 (height) based on the data in the matrix. If the value in a matrix cell is odd, draw a yellow rectangle in its grid location in the window and if the value in a matrix cell is even, draw a blue rectangle in its grid location in the window.

    for matrix = [[0,2,1,3],[4,5,6,7],[9,3,5,1],[6,2,7,0]]

  4. [Open ended.] Draw a picture with 100 rectangles of different sizes drawn at random places in the window with random colors.