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Reading of graphical output of another application (D7)

Posted on 2011-09-30
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Last Modified: 2013-11-22
I have a very old application that doesn't have logging capabilities. It has only graphical representation of information needed. I attached link to a picture where different readings can be seen.
Vertical indicator with scale that has zero in the middle.

I need a code that can read and log that indicator's reading to a file, with frequency up to once per second.

I have an idea in general how it should be done but no idea how to code it.

So, in general:
1. it needs to get window handle base on window's name
2. make screenshot of rectangle one pixel wide and 100% of indicator's high
3. find current reading (background is constant, so, the needed reading is a border between color and background)
4. write it to a log file

I hope the description is clear.

sc.gif
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Question by:3axap
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6 Comments
 
LVL 25

Expert Comment

by:epasquier
ID: 36895970
don't have time to piece it together. you had the methodology right.
here is how to get a window by its title
function SearchMainWindowByName(Start:String;Mid:String='';UpC:boolean=True):THandle;
type
 RR=Record
     S,M:String;
     L:integer;
     U:boolean;
     hWindow:HWND;
    end;
 pRR=^RR;
Var
 R:RR;
 function EnumProcess(hHwnd: HWND; lParam : integer): boolean; stdcall;
 var
  pPid : DWORD;
  title, ClassName : string;
  R:pRR;
 begin
  //if the returned value in null the
  //callback has failed, so set to false and exit.
  if (hHwnd=0) then result := false else
   begin
    R:=pRR(lParam);
    //additional functions to get more
    //information about a process.
    //get the Process Identification number.
{$ifdef VER140}
      GetWindowThreadProcessId(hHwnd,pPid);
{$else}
      GetWindowThreadProcessId(hHwnd,@pPid);
{$endif}
    SetLength(ClassName, 255);
    SetLength(ClassName,
              GetClassName(hHwnd,
                           PChar(className),
                           Length(className)));
    SetLength(title, 255);
    SetLength(title, GetWindowText(hHwnd, PChar(title), Length(title)));
    //Display the process information
    //by adding it to a list box
    if Assigned(SearchWindowList) Then SearchWindowList.Add
      ('Class Name = ' + className +
       '; Title = ' + title +
       '; HWND = '+ IntToStr(hHwnd) +
       '; Pid = ' + IntToStr(pPid));
    if R^.U Then
     begin
      Title:=UpperCase(title);
      ClassName:=UpperCase(ClassName);
     end;
    if Copy(title,1,R^.L)=R^.S Then
     begin
      if (R^.M='') Or (Pos(R^.M,title)>0)
        Then R^.hWindow:=hHwnd;
     end Else
    if Copy(ClassName,1,R^.L)=R^.S Then
     begin
      if (R^.M='') Or (Pos(R^.M,ClassName)>0)
        Then R^.hWindow:=hHwnd;
     end;
    Result := R^.hWindow=0;
  end;
 end;
begin
 R.hWindow:=0;
 if UpC Then
  begin
   R.S:=UpperCase(Start);
   R.M:=UpperCase(Mid);
  end Else
  begin
   R.S:=Start;
   R.M:=Mid;
  end;
 R.L:=Length(Start);
 R.U:=Upc;
 if Assigned(SearchWindowList) Then SearchWindowList.Clear;
 EnumWindows(@EnumProcess,Integer(@R));
 Result:=R.hWindow;
end;

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LVL 25

Expert Comment

by:epasquier
ID: 36895971
here is how to get the window as bitmap

ScreenShot(WinHandle, Bmp, True ); // true = client area
procedure ScreenShot(hWin:THandle;destBitmap : TBitmap;ClientArea:Boolean=True);
var
   w,h : integer;
   DC : HDC;
   r : TRect;
begin
 if ClientArea then
  begin
   dc := GetDC(hWin) ;
   GetClientRect(hWin,r);
  end else
  begin
   dc := GetWindowDC(hWin) ;
   GetWindowRect(hWin,r) ;
  end;
 w := r.Right - r.Left;
 h := r.Bottom - r.Top;
 try
  destBitmap.Width := w;
  destBitmap.Height := h;
  BitBlt(destBitmap.Canvas.Handle,
         0,
         0,
         destBitmap.Width,
         destBitmap.Height,
         DC,
         0,
         0,
         SRCCOPY) ;
 finally
  ReleaseDC(hWin, DC) ;
 end;
end;

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LVL 25

Accepted Solution

by:
epasquier earned 400 total points
ID: 36895973
then with the bitmap, you use bmp.canvas.Pixels[X,Y] and test the color to find when it's not grey (starting from top to middle and bottom to middle)
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Author Comment

by:3axap
ID: 36896017
Pasquier, thank you.
Actually "test the color to find when it's not grey (starting from top to middle and bottom to middle)" is the hardest part for me :o)
I'll try to get those peices together.

Speed wise, base on your experience, is this methodology optimal enough to run with 1Hz frequency and don't eat much CPU time?
0
 
LVL 25

Expert Comment

by:epasquier
ID: 36896045
sure.
0
 
LVL 27

Assisted Solution

by:Sinisa Vuk
Sinisa Vuk earned 100 total points
ID: 36909484

For detecting colors:

...
bmp: TBitmap;
...
if bmp.Canvas.Pixels[x, y] = clGray then ....

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