Re: Getting screen display pixel color value [SOLVED]
lazarus / 21-General

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Davo · 2021-08-19 04:35

I'm running Lazarus version #:2.0.10; FPC version: 3.2.0; SVN
Revision: 63526. While this may possibly be a bit dated I doubt that
that fact is causing my difficulty.

Given :
1. a transparent form that covers the display screen,
2. the form has a visible square shape three pixels wide and three
pixels tall,
3. the square can be moved across the display screen at will,
4. it is possible to determine the square's current screen coordinates
is it possible to determine the pixel RGB value of the screen display
that underlies (say) the square's centre pixel?

The following code obtained from the Forum seems to be what I want :
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 uses 
Classes, SysUtils, Forms, Controls, Graphics, Dialogs, ExtCtrls,
StdCtrls,  Windows; function TForm1.ReadScreenColor(const X, Y:
integer): TColor;var  ScreenDC: HDC;  SaveBitmap: TBitmap;begin 
SaveBitmap := TBitmap.Create;  try    SaveBitmap.SetSize(Screen.Width,
Screen.Height);    ScreenDC := GetDC(0);    try     
SaveBitmap.LoadFromDevice(ScreenDC);    finally      ReleaseDC(0,
ScreenDC);    end;    Result := SaveBitmap.Canvas.Pixels[X, Y]; 
finally    SaveBitmap.Free;  end;end; However I get a compiler error
at the line SaveBitmap := TBitmap.create; The error is “identifier
idents no member “Create”. Clearly I'm doing something wrong. Any help
will be much appreciated.

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dseligo · 2021-08-19 06:22

In uses section put Windows in front of Graphics, like that:
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 uses 
Classes, SysUtils, Forms, Controls, Windows, Graphics, Dialogs,
ExtCtrls, StdCtrls;

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Davo · 2021-08-19 06:49

Many thanks dseligo. Works just fine now.

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paweld · 2021-08-19 07:36

or:
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 var  //... 
SaveBitmap: Graphics.TBitmap;begin  SaveBitmap :=
Graphics.TBitmap.Create;  //...

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Davo · 2021-08-21 03:04

Thanks psweld. Yes works also. Much appreciated.