Painfully elementary
lazarus / 39-Graphics

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SillyOldDragon · 2012-11-20 18:16

I am having a problem with getting started in Graphics.  What I would
love to see is this (as vanilla as possible).
The screen is x pixels wide.  The screen is y pixels high.
I want to put one red pixel at x=45 and y = 30 on a black background.
Would someone be kind enough to answer with a full program that does
just that.  (The calculations for what I really want to do I can
handle in my sleep but it's the pieces that deal witht the screen that
have lost me.)

All of the Uses, Types, Vars and the picky forms of asssignment needed
to do one pixel to a certain point have got me going in circles.

I haven't programmed in Pascal in 25+ years and I am SO HAPPY to see
it's still alive. 

Thank you

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eny · 2012-11-20 18:51

Have a look at the painter class in here 
http://wiki.lazarus.freepascal.org/Lazarus_Mazes_demo

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anis2505 · 2012-11-20 20:05

Hi,

Here is 2 example to draw:

1) Drawing to the form directly
2) Drawing to a custom control using Bitmap

http://www.4shared.com/zip/z-CRkzVM/lazGraphics.html

Take a look to the Wiki everything is explained well on it
http://wiki.lazarus.freepascal.org/Developing_with_Graphics

Regards

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SillyOldDragon · 2013-01-10 02:53

Wharever the file was on 4share - it won't download.  Is there
anything out there that (given a long time history with Turbo Pascal)
will just not worry about portability or frills and just say "put red
dot here"?

I just need one VERY vanilla plain example.  "Program ..... to .....
end." .

Windows XP  screen 1024x768  32 bit colors

Thank you

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Blaazen · 2013-01-10 03:08

Ok, so start a new project and put TPaintBox on a form (it's on the
Additional Palette) - it adds component PaintBox1.
Replace all code with this:
Code: [Select]unit Unit1;       
{$mode objfpc}{$H+}

interface

uses
  Classes, SysUtils, FileUtil, Forms, Controls, Graphics, Dialogs,
ExtCtrls;

type    
  { TForm1 }
  TForm1 = class(TForm)
    PaintBox1: TPaintBox;
    procedure PaintBox1Paint(Sender: TObject);
  private
    { private declarations }
  public
    { public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.lfm}

{ TForm1 }

procedure TForm1.PaintBox1Paint(Sender: TObject);
begin
  with PaintBox1.Canvas do
    begin
      Brush.Color:=clWhite;
      FillRect(0, 0, Width, Height);
      Pixels[10, 10]:=clRed;             
    end;
end;

end.
And go to object inspector, select tab Events and assign
PaintBox1.OnPaint event to PaintBox1Paint method.
Now hit F9 and it will run project. Hopefully, there should be a white
rectangle with a red pixel at [10, 10].

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User137 · 2013-01-10 08:45

My favorite so far was TImage. Things are drawn to
image1.Picture.Bitmap.Canvas. Note that it is very different from
image1.Canvas, which is doing nonpermament changes, like drawing on
form or Picturebox, and sometimes this is bad.

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Leledumbo · 2013-01-10 11:43

I would go for Blaazen solution if what you need is to draw the
"screen" frequently as TPaintBox is meant for that. TImage would be
too slow as it's intended for static image. Well, doing it on an
OpenGL canvas might be the fastest though but I guess you don't need
that far.