From: "Marvin Gülker" <sutniuq@...>
Date: 2009-11-15T20:59:44+09:00
Subject: Re: How to do a getPixel on Win32 using Ruby?

Jian Lin wrote:
> Marvin Gülker wrote:
> 
>> 
>> Do you want to draw onto the screen?
>> 
>> If so, I think you should use a GUI toolkit, create a maximized window, 
>> without a title bar and border, and then draw onto it.
> 
> can wxRuby get a pixel's color value off from the screen too?  (not 
> window but the screen)

If you create the window like I showed, it will fill the *entire* 
screen. There's nothing else than the window to see (not even the 
taskbar!), so it's equivalent if you get the pixel from your window or 
the screen. And so does it work:
-------------------------
require "wx"

class MyApp < Wx::App
  include Wx

  def on_init
    @mainwindow = Frame.new(nil, -1, "", DEFAULT_POSITION, DEFAULT_SIZE, 
MAXIMIZE)
    @mainwindow.background_colour = BLACK
    Timer.after(3000) do
      @mainwindow.paint do |dc|
        dc.pen = WHITE_PEN
        dc.draw_line(0, 0, 500, 500)
        #Get the pixel color at (100|10) which should be black.
        col = Colour.new(255, 255, 255) #This means white
        dc.get_pixel(100, 10, col)
        p col #=> (0, 0, 0) #This means black
      end
    end
    Timer.after(5000){@mainwindow.close}
    @mainwindow.show
  end

end

x = MyApp.new
x.main_loop
------------------------
The #get_pixel method seems to be directly imported from C, because it 
works like it would require a pointer. However, it works. The method to 
set a pixel directly, is #draw_point.

Marvin
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