edu_draw

Simple ruby drawing API based on gosu meant for educational purposes.

Install

    gem install edu_draw

If you run into any problems its most likely because of gosu, as this is the only runtime dependency of edu_draw.

Usage

There are only two classes: A sheet to draw on and a pen to draw with. The sheet is also the window. Unfortunately, the underlying engine only supports really one window, so you should only create one sheet per program. This is done as follows: First, load edu_draw into your program

    require "edu_draw"

Then, create the sheet

    sheet = EduDraw::Sheet.new x: 500, y: 600, title: "It works"

Now that you have a sheet, that is 500 pixels wide and 600 pixels high, you can create pens for this sheet to draw on.

    green_pen = sheet.new_pen x: 100, y: 20

Green is the default color for pens but you can have any color using the color parameter.

Now it's time to draw a rectangle!

    green_pen.move 100
    green_pen.turn_right 90
    green_pen.move 80
    green_pen.turn_right 90
    green_pen.move 100
    green_pen.turn_right 90
    green_pen.move 80

When you are done drawing, you have to make one final call to the sheet, to actually display the window with your drawings.

    sheet.show

The whole program looks like this:

    require "edu_draw"

    sheet = EduDraw::Sheet.new x: 500, y: 600, title: "A beautiful rectangle"
    green_pen = sheet.new_pen(x: 100, y: 20)

    green_pen.move 100
    green_pen.turn_right 90
    green_pen.move 80
    green_pen.turn_right 90
    green_pen.move 100
    green_pen.turn_right 90
    green_pen.move 80

    sheet.show

Areas / Filled shapes

You can also draw filled or party-filled shapes. Here is an short example, that can be also found in the examples folder:

    require "edu_draw"

    sheet = EduDraw::Sheet.new(x: 150, y: 150)
    pen = sheet.new_pen(x: 52, y: 10)

    # Every move in the fill-block will create a filled a shape
    pen.fill do
        5.times do
            pen.move 40
            pen.turn_right 36
        end
    end

    # Every move out of the fill block just draws a line
    # Those 10 moves result in a half-filled decagon
    5.times do
        pen.move 40
        pen.turn_right 36
    end


    sheet.show

Animations

You can even draw animated shapes. Here is an short example, that can be also found in the examples folder:

    require "edu_draw"

    sheet = EduDraw::Sheet.new(x: 150, y: 150)

    # Instead of using sheet.new_pen, now you create a new_animation_pen
    pen = sheet.new_animation_pen(x: 75, y: 75)

    # Here you define what happens in the beginning of each frame
    pen.each_frame do
        pen.turn_right 1
    end

    # Now you define what the pen should draw each frame
    # It is important to leave the pen in a state, where
    # it can start drawing on the next frame, that's why
    # the pens moves back, even though it does not draw
    # any actual lines.
    pen.draw_frame do
        pen.move 50
        pen.move -50
    end


    # You're set. Now just show the sheet as usual and enjoy
    # the wonderfully spinning line you just drew.
    sheet.show

Changelog

• 2.0.0
  • Adds ability to fill shapes. See examples/areas.rb
  • Adds ability to draw animated shapes. See examples/animations.rb
  • Makes state of pen writable
  • Greatly improves documentation

Contributing

Feel free to contribute anything, may it be better tests, better documentation or more features. As you can see, I tried to keep the code tidy so it is appreciated if you'd do the same. Just add a pull request and we will make it work. Oh, and don't forget to have fun ;)

Kudos

Kudos to the wonderful people behind Gosu. You do some great work.