Getting Color of certain pixel on screen
lazarus / 39-Graphics

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dietmar · 2021-07-22 17:06

Hi,

I want
a) to determine the current background color value of a form
b) to determine the color (RGB, TColor) of a certain point on the
screen.

Can you help?

Thx
Dietmar

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winni · 2021-07-22 19:17

Hi!

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 
ScreenDC: HDC;  RGB, BGcol : TColor; begin    // a)   BGcol :=
Form1.Color;    // b) get color of pixel  10/20  ScreenDC :=
GetDC(0);  RGB := GetPixel(ScreenDC 10, 20);  end;
Winni

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440bx · 2021-07-22 19:27

Quote from: dietmar on July 22, 2021, 07:06:57 pmI want
a) to determine the current background color value of a form
b) to determine the color (RGB, TColor) of a certain point on the
screen.
I can only tell you how to do it using the Windows API.  For a
multiplatform answer, someone else will have to provide it.

for (a) use GetClassLongPtr using GCL_HBRBACKGROUND

for (b) use GetPixel

both of those functions are documented by MS.  Use Google to get to
the detailed documentation.

HTH.

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wp · 2021-07-22 20:48

The following code is taken from the mbColorLib package and is cross-
platform:

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 function
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;

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winni · 2021-07-22 20:52

Hi!

Yes, that is the long version for a HowTo-Book.

I showed the short version above.

Winni

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dietmar · 2021-07-22 20:55

Thank you all!

Dietmar

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wp · 2021-07-22 20:57

Quote from: winni on July 22, 2021, 10:52:02 pmI showed the short
version above.
To my knowledge GetPixel is a function in the Windows unit. If it were
cross-platform, it would be found in LCLIntf.