Splitting Picture into Quads using Quadtree ?
lazarus / 39-Graphics

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Boleeman · 2026-04-06 04:58

Was wondering if anyone has been able to use Lazarus to visually split
a loaded picture into Quads using Quadtree (as shown in attachments) ?

There are plenty of Python and C++ codes, but nothing much in Lazarus
(Pascal) or Delphi.

Corpsman had an example of compressing a grayscale bmp image using the
Quadtree Algorithm, but I wanted to load a color png and have it
dissected into quads using Quadtree.

Here are some nice Python implementations:
https://github.com/AlexEidt/Quart      (this also has a video at the
bottom)
https://github.com/fogleman/Quads


But how to go about doing it in Lazarus using TBgrabmp?

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Boleeman · 2026-04-12 00:43

Here is a Lazarus quadtree program that uses a set of points.

It was made by Corpsman.


Still trying the work out how to do it for loaded coloured png images
!

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Dzandaa · 2026-05-22 11:01

Hi Eddie,

Try this program.

A big thank you to my wife (she's a PH d mathematician) who helped me
fix the last bug

Lower Threshold = Better Resolution

Pan with left button, zoom with the middle button.

Just tested on Windows.


B->

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LeP · 2026-05-23 09:52

@DZandaa,

thanks for the source.
I tried quickly and seems that there some issues about x, y
coordinates (may be exchanged) and generate an AV in various point of
your source.

Try with an image with Height <> Width.

I have not time now to debug and report the corrections, but I'll do
in the next time.

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Dzandaa · 2026-05-23 10:37

Hi
@Lep:

Thank  you for testing my program.

Effectively, I just tested the algorithm on squares Pictures !!!

The x and y of the Double array  are reversed.

I corrected that.

B->

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Dzandaa · 2026-05-25 10:38

Hi,
Here is a new version showing rectangles boundaries

Have a nice day.

B->

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ADMGNS · 2026-06-06 20:44

hello

several years ago, i'd studied on quadtree algorithm which was on
video codecs, but it was in D7.

pls see attachment

regs

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Dzandaa · 2026-06-07 10:30

Hi,
@ADMGNS :

Sorry, I don't use Delphi, just Pascal Lazarus.

And the conversion doesn't work well.


B->

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ADMGNS · 2026-06-07 11:16

hello again

lazarus conversion plus some minor changes manually, it works
minimally now. here is it..

regs

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Dzandaa · 2026-06-07 16:16

Hi,

@ADMGNS:

It works now, but if I load an image and click cmdColorCount, I have a
crash here:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i   for k:=0
to nSize1-1 do  begin    c := (p^ shl 8) shr 8; // ie, c := c and
$00FFFFFF; // <---- here    inc(hist[c]);     inc(p);  end; 
Perhaps the size of the picture is too big.

Also, you can test with

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i  for k:=0
to Pred(nSize1) do 
I don't know if it is faster.
B->