How do I make a paint bucket tool (FloodFill?) [SOLVED]
lazarus / 39-Graphics

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nsunny · 2010-12-20 07:32

Hi guys,

Your previous response has helped me a lot.

As I told earlier that I am making a paint program like MS Paint. And
the MS Paint has a pretty nice tool which they call it "Fill with
color". Which allows to fill a certain area of same color to be filled
with the foreground color. I am trying to do this, but failed. PLease
look at the screenshot:

(http://d.imagehost.org/t/0398/ms-paint-fill-tool-lazarus.jpg)

I have tried the following code:

Code: [Select]procedure TForm1.Button1Click(Sender: TObject);
begin
  form1.Canvas.Rectangle(0, 0, 100, 100);
  form1.Canvas.Ellipse(50, 50, 100, 100);
  form1.Canvas.FloodFill(3, 3, clRed, fsSurface);
end;

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fabienwang · 2010-12-20 08:20

before the Canvas.Rectangle (or any form Ellipse, etc.), you have to
define the fill color in Canvas.Brush.Color property

Regards,
FabienWang

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nsunny · 2010-12-20 08:47

Quote from: FabienWang on December 20, 2010, 09:20:21 ambefore the
Canvas.Rectangle (or any form Ellipse, etc.), you have to define the
fill color in Canvas.Brush.Color property

Regards,
FabienWang
Thank you. But Suppose that I have opened a .bmp/bitmap file
containing the rectangle and the circle, then how should I Fill the
rectangle? (and not the circle?)

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Leledumbo · 2010-12-20 09:44

QuoteThank you. But Suppose that I have opened a .bmp/bitmap file
containing the rectangle and the circle, then how should I Fill the
rectangle? (and not the circle?)In that case, let TBitmap draws it for
you. Anyway, .bmp is just a map of pixels and is a direct
representation of the image, so you just follow the pixels.

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Blaazen · 2010-12-20 22:22

AFAIK this is usually done with recursive algorithm. You have start
point with some color and you check colors of neighbouring pixels
(left, right, top, down). If color is same (exactly or in some
tolerancy) you change it to your color and continue. Because procedure
calls itself, there is risk of stack overflow, so the algorithm must
be well optimalised. Rather use google, for example on wiki:
http://en.wikipedia.org/wiki/Flood_fill

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nsunny · 2010-12-21 04:56

Quote from: Blaazen on December 20, 2010, 11:22:18 pmAFAIK this is
usually done with recursive algorithm. ...
Ummm... so I will have to write my own algorithm?  But what does the
FloodFill() do?

If I must write an algorithm, how can I make it cross-platform? (plus,
it would be better if there is tolerance option.  )

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Blaazen · 2010-12-21 16:21

Now I see there is any FloodFill procedure in unit Graphics. So add
"Graphics" to your "uses" section and try it (I didn't).

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mmab · 2010-12-21 23:50

Please read
http://en.wikipedia.org/wiki/Flood_fill

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typo · 2010-12-22 01:10

Code: [Select]  Canvas.Brush.Color := clNone;
  Canvas.Rectangle(0, 0, 100, 100);
  Canvas.Ellipse(0, 0, 50, 50);
  Canvas.Brush.Color := clBlack;
  Canvas.FloodFill(3, 3, clBlack, fsBorder);

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nsunny · 2010-12-22 02:57

Quote from: typo on December 22, 2010, 02:10:56 amCode: [Select]
 Canvas.Brush.Color := clNone;
  Canvas.Rectangle(0, 0, 100, 100);
  Canvas.Ellipse(0, 0, 50, 50);
  Canvas.Brush.Color := clBlack;
  Canvas.FloodFill(3, 3, clBlack, fsBorder);
  I just love u bro!! This worked like a charm. Thanks!!!

I see that the second "Canvas.Brush.Color" is the fill color and the
Tcolor in the FloodFill is the replacement color. Thank you very much.

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focuz · 2011-01-05 21:15

Yeah thanks, I was looking for this too

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typo · 2011-01-05 21:24

Code: [Select]// replaces any color with clYellow at the mouse
position
procedure TForm1.FormMouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  Canvas.Brush.Color := clYellow;
  Canvas.FloodFill(x, y, Canvas.Pixels[x,y], fsSurface);
end;

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iguru · 2011-05-12 16:18

Uaaaa     
FloodFill work only on Win32!!! Now i tested on Linux (Kubuntu -
Natty) and this not working.