Problem with FPC

[matrix1233 0]

Hi,

Am using Lazarus(FPC) and am trying to execute the Demo29 (work perfectly on delphi). the problem when i open Image and i Execute (Use Device Context Unchecked) the program go to the end and Image1.Picture.Graphic.LoadFromStream(_stream);  raise an exception Wrong Image Format  

 if (Image1.Picture.Graphic = nil) or Image1.Picture.Graphic.Empty then
    raise Exception.Create('You must first select an image');
  PythonEngine1.ExecStrings(Memo1.Lines);
  _im := MainModule.ProcessImage(ImageToPyBytes(Image1.Picture.Graphic));
  if not chkUseDC.Checked then
  begin
    // We have to call PyString_AsStringAndSize because the image may contain zeros
    with GetPythonEngine do begin
      pargs := MakePyTuple([ExtractPythonObjectFrom(_im)]);
      try
        presult := PyEval_CallObjectWithKeywords(
            ExtractPythonObjectFrom(MainModule.ImageToBytes), pargs, nil);
        try
          if (P = nil) or (PyBytes_AsStringAndSize(presult, P, Len) < 0) then begin
            ShowMessage('This does not work and needs fixing');
            Abort;
          end;
        finally
          Py_XDECREF(pResult);
        end;
      finally
        Py_DECREF(pargs);
      end;
    end;

    _stream := TMemoryStream.Create();
    try
      _stream.Write(P^, Len);
      _stream.Position := 0;
      Image1.Picture.Graphic.LoadFromStream(_stream);
    finally
      _stream.Free;
    end;
  end
  else
  begin
    Image1.Picture.Bitmap.SetSize(Image1.Width, Image1.Height);
    _dib := Import('PIL.ImageWin').Dib(_im);
    Image1.Picture.Bitmap.SetSize(Image1.Height, Image1.Width);
    _dib.expose(NativeInt(Image1.Picture.Bitmap.Canvas.Handle));
  end;  

How can i correct that ?  Thanks .

Edited December 22, 2020 by matrix1233

[Fr0sT.Brutal 900]

Just save the _stream to disc and see what it contains

[matrix1233 0]

Hi

the file is saved and his size is 197k and the content is "þîþîþîþîþî.." (from the begin to end) 

 

[Fr0sT.Brutal 900]

So you receive garbage. You'll have to debug that stage

[Virgo 18]

Looking original code in unit1.pas from git: value of P is undefined there, because it is never initialized. What happens, if you add

p := nil;

at the beginning of Button2Click?

[matrix1233 0]

if  p := nil then i have the msg 'This does not work and needs fixing' 

 

 if (Image1.Picture.Graphic = nil) or Image1.Picture.Graphic.Empty then
    raise Exception.Create('You must first select an image');
  PythonEngine1.ExecStrings(Memo1.Lines);
  _im := MainModule.ProcessImage(ImageToPyBytes(Image1.Picture.Graphic));
  if not chkUseDC.Checked then
  begin
     P := nil;
    // We have to call PyString_AsStringAndSize because the image may contain zeros
    with GetPythonEngine do begin
      pargs := MakePyTuple([ExtractPythonObjectFrom(_im)]);
      try
        presult := PyEval_CallObjectWithKeywords(
            ExtractPythonObjectFrom(MainModule.ImageToBytes), pargs, nil);
        try
          if (P = nil) or (PyBytes_AsStringAndSize(presult, P, Len) < 0) then begin
            ShowMessage('This does not work and needs fixing');
            Abort;
          end;
        finally
          Py_XDECREF(pResult);
        end;
      finally
        Py_DECREF(pargs);
      end;
    end;

    _stream := TMemoryStream.Create();
    try
      _stream.Write(P^, Len);
      _stream.Position := 0;
      _stream.SaveToFile('test.jpeg');
     // Image1.Picture.Graphic.LoadFromStream(_stream);
    finally
      _stream.Free;
    end;
  end
  else
  begin
    Image1.Picture.Bitmap.SetSize(Image1.Width, Image1.Height);
    _dib := Import('PIL.ImageWin').Dib(_im);
    Image1.Picture.Bitmap.SetSize(Image1.Height, Image1.Width);
    _dib.expose(NativeInt(Image1.Picture.Bitmap.Canvas.Handle));
  end;     

 

[matrix1233 0]

i think that the problem is on MainModule.ImageToBytes  because on Delphi when i try to display it to a memo (Memo3.Lines.Add(MainModule.ImageToBytes); ) i have <function ImageToBytes at 0x00000000068DDCA0> but when i try the same code on Lazarus i have nothing . any idea how can i resolve on lazarus ?

[Virgo 18]

Right, there was or, so p value was red herring. Although (p=nil) check is invalid anyway, because value of p is undefined there.

[matrix1233 0]

the problem is not P, i think that is just  MainModule.ImageToBytes like i explained above .. any idea ? 

Edited December 22, 2020 by matrix1233

[matrix1233 0]

any solution ?

[Virgo 18]

After reading Python documentation I do not understand, how it can work in Delphi.

Move

          _stream := TMemoryStream.Create();
          try
            _stream.Write(P^, Len);
            _stream.Position := 0;
            Image1.Picture.Graphic.LoadFromStream(_stream);
          finally
            _stream.Free;
          end;

before

        finally
          Py_XDECREF(pResult);
        end;

 

P will be reference to internal buffer in pResult and Py_XDECREF(pResult); frees that memory.

[matrix1233 0]

Thanks, it's work!

[Virgo 18]

But also, from

if (P = nil) or (PyBytes_AsStringAndSize(presult, P, Len) < 0) then begin

 

"(p = nil) or" should be removed, because P is uninitialized, which only means, that it causes error, when P happens coincidentally initialize to nil.

[matrix1233 0]

yes i see! .. between Delphi and Lazarus the result of execution are different for example this code below With Delphi work perfectly and with lazarus it doesn't work and it say that  ( 'This does not work and needs fixing' ) generated by the test on PyBytes_AsStringAndSize. Any idea for this example why it's different ? 
   

var _im : Variant;
_dib : Variant;
 i:integer;
 pargs: PPyObject;
 pResult :PPyObject;
 P : PAnsiChar;
 _stream:TmemoryStream;
 Len : NativeInt;
 SPython:TstringList;
begin

SPython:=TstringList.Create;
SPython.Add('from io import BytesIO');
SPython.Add('from PIL import ImageGrab');
SPython.Add('def screenshot():');
SPython.Add('   im = ImageGrab.grab()');
SPython.Add('   stream = BytesIO()');
SPython.Add('   im.save(stream, "BMP")');
SPython.Add('   return stream.getvalue()');
SPython.Add('screenshot()');
PythonEngine1.ExecStrings(SPython);

 with GetPythonEngine do begin
        try
          pResult := ExtractPythonObjectFrom(MainModule.screenshot());
          if (PyBytes_AsStringAndSize(pResult, P, Len) < 0)   then begin
            ShowMessage('This does not work and needs fixing');
            Abort;
          end;
        finally
         _stream := TMemoryStream.Create();
          try
            _stream.Write(P^, Len);
            _stream.Position := 0;
            Memo2.Lines.add(_stream.Size.ToString);
            Image1.Picture.LoadFromStream(_stream);
            application.ProcessMessages;
          finally
            _stream.Free;
          end;
        end;
end;

 

[pyscripter 689]

The fpc support for custom variants is incomplete.  See the fpc section at SupportedPlatforms · pyscripter/python4delphi Wiki (github.com).

 

Does it work if you store 

MainModule.screenshot()

to a variable and then call ExtractPythonObjectFrom like in the previous example?

 

Edited December 23, 2020 by pyscripter

[matrix1233 0]

Hi, i stored MainModule.screenshot() to a variable _im like you asked and it doesn't work (See the first code below)  but when i change the line where pResult are affected with presult := PyEval_CallObjectWithKeywords(ExtractPythonObjectFrom(MainModule.screenshot()), nil, nil), it work on lazarus . (See the second code below) .

i think that ExtractPythonObjectFrom are only needed to do the job and adding PyEval_CallObjectWithKeywords is not needed in this case but lazarus have some bugs .. we can perhaps correct this ?

 

var _im : Variant;
_dib : Variant;
 i:integer;
 pargs: PPyObject;
 pResult :PPyObject;
 P : PAnsiChar;
 _stream:TmemoryStream;
 Len : NativeInt;
 SPython:TstringList;
begin

SPython:=TstringList.Create;
SPython.Add('from io import BytesIO');
SPython.Add('from PIL import ImageGrab');
SPython.Add('def screenshot():');
SPython.Add('   im = ImageGrab.grab()');
SPython.Add('   stream = BytesIO()');
SPython.Add('   im.save(stream, "BMP")');
SPython.Add('   return stream.getvalue()');
SPython.Add('screenshot()');
PythonEngine1.ExecStrings(SPython);
 _im:=MainModule.screenshot();
 with GetPythonEngine do begin
        try
          pResult := ExtractPythonObjectFrom(_im);
          if (PyBytes_AsStringAndSize(pResult, P, Len) < 0)   then begin
            ShowMessage('This does not work and needs fixing');
            Abort;
          end;
        finally
         _stream := TMemoryStream.Create();
          try
            _stream.Write(P^, Len);
            _stream.Position := 0;
            Memo2.Lines.add(_stream.Size.ToString);
            Image1.Picture.LoadFromStream(_stream);
            application.ProcessMessages;
          finally
            _stream.Free;
          end;
        end;
end;

 

var _im : Variant;
_dib : Variant;
 i:integer;
 pargs: PPyObject;
 pResult :PPyObject;
 P : PAnsiChar;
 _stream:TmemoryStream;
 Len : NativeInt;
 SPython:TstringList;
begin

SPython:=TstringList.Create;
SPython.Add('from io import BytesIO');
SPython.Add('from PIL import ImageGrab');
SPython.Add('def screenshot():');
SPython.Add('   im = ImageGrab.grab()');
SPython.Add('   stream = BytesIO()');
SPython.Add('   im.save(stream, "BMP")');
SPython.Add('   return stream.getvalue()');
SPython.Add('screenshot()');
PythonEngine1.ExecStrings(SPython);

 with GetPythonEngine do begin
        try
         presult := PyEval_CallObjectWithKeywords(ExtractPythonObjectFrom(MainModule.screenshot()), nil, nil);
          if (PyBytes_AsStringAndSize(pResult, P, Len) < 0)   then begin
            ShowMessage('This does not work and needs fixing');
            Abort;
          end;
        finally
         _stream := TMemoryStream.Create();
          try
            _stream.Write(P^, Len);
            _stream.Position := 0;
            Memo2.Lines.add(_stream.Size.ToString);
            Image1.Picture.LoadFromStream(_stream);
            application.ProcessMessages;
          finally
            _stream.Free;
          end;
        end;
end;