Lazarus GDI+ problem. Access Violation
lazarus / 39-Graphics

----------------------------------------------------------------------
Nick00 · 2023-04-12 06:47

I am porting an application from Delphi to Lazarus. There was a
problem with the following piece of code:
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
GDIPAPI, GDIPOBJ;...var ist:IStream;    ms:TMemoryStream;   
img:TGPImage;begin    ...    //загрузка из БД blob поля в поток   
(DS.FieldByName('IMAGE') as TBlobField).SaveToStream(ms);   
//создание TGPImage    ms.Position:=0;   
ist:=TStreamAdapter.Create(ms);    img:=TGPImage.Create(ist); // на
этой строке возникает исключение    ...end;The problem is throwing an
exception External: Access Violation... Write of address 00000000.
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 TGPImage
constructor:constructor TGPImage.Create(stream: IStream; 
useEmbeddedColorManagement: BOOL = FALSE);begin  nativeImage := nil; 
if (useEmbeddedColorManagement) then    lastResult :=
GdipLoadImageFromStreamICM(stream, nativeImage)  else lastResult :=
GdipLoadImageFromStream(stream, nativeImage);end;The modules GDIPAPI,
GDIPOBJ are identical for Delphi and Lazarus, except for the line
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 {$IFDEF
FPC} {$MODE Delphi} {$ENDIF}in modules for Lazarus.
For an ms stream, ms.Size in Delphi = ms.Size in Lazarus for a single
database entry. Interestingly, if write
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
ms.Position:=1;then an exception is not thrown, well, in img, of
course, garbage.
Who has any ideas how to deal with the problem?

----------------------------------------------------------------------
marcov · 2023-04-12 10:33

If you save the memory stream to disc after the ms.position:=0, is the
result a valid image or does it have some bytes prepended?

----------------------------------------------------------------------
Nick00 · 2023-04-13 02:21

The IMAGE field contains an image in emf format. If i do
ms.SaveToFile, the valid image is saved to the file.

----------------------------------------------------------------------
Nick00 · 2023-05-02 03:12

I found out that the problem occurs when rendering the emf / wmf
format. JPEG Rendered without problems. Attached is a test project.
https://drive.google.com/file/d/1Ee301-
ej4iW25z7isH8eW37r6ksZe3P5/view?usp=share_link

----------------------------------------------------------------------
Jurassic Pork · 2023-05-02 05:43

hello,
for GDI+ you can try the GDIPlus-Library-for-Delphi-and-Lazarus. There
is a package for Lazarus. Exemple :
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
implementationuses  GDIPlus; {$R *.lfm} { TForm1 } procedure
TForm1.PaintBox1Paint(Sender: TObject);var img:IGPImage;    g:
IGPGraphics;begin  img := TGPImage.Create('image.emf'); 
g:=TGPGraphics.Create(PaintBox1.Canvas.Handle);  g.SetPageUnit
(UnitPixel); 
g.DrawImage(img,0,0,PaintBox1.Width,PaintBox1.Height); end;      

Friendly, J.P

----------------------------------------------------------------------
Nick00 · 2023-05-02 06:47

Quote from: Jurassic Pork on May 02, 2023, 07:43:00 amhello,
for GDI+ you can try the GDIPlus-Library-for-Delphi-and-Lazarus. There
is a package for Lazarus. Exemple :
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
implementationuses  GDIPlus; {$R *.lfm} { TForm1 } procedure
TForm1.PaintBox1Paint(Sender: TObject);var img:IGPImage;    g:
IGPGraphics;begin  img := TGPImage.Create('image.emf'); 
g:=TGPGraphics.Create(PaintBox1.Canvas.Handle);  g.SetPageUnit
(UnitPixel); 
g.DrawImage(img,0,0,PaintBox1.Width,PaintBox1.Height); end;      

Friendly, J.P            

Thanks for the answer.
Your code works with my version of the library too. However, in both
versions of the library, an error occurs if the image is loaded from a
stream.
Loading from a file doesn't work for me as the images are stored in
the database in binary form.

----------------------------------------------------------------------
loaded · 2023-05-02 16:01

Quote from: Nick00 on May 02, 2023, 08:47:06 amThanks for the answer.
Your code works with my version of the library too. However, in both
versions of the library, an error occurs if the image is loaded from a
stream.
Loading from a file doesn't work for me as the images are stored in
the database in binary form.


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
GdiPlus,Activex,Comobj;  function MemoryStreamToIStream(const AStream:
TMemoryStream): IStream;var  Output: IStream;  Data: Pointer;  Size:
Longint;  test:Qword;begin  Data := AStream.Memory;  Size :=
AStream.Size;  OleCheck(CreateStreamOnHGlobal(0, True, Output));  try 
  OleCheck(Output.Write(Data, Size, nil));    OleCheck(Output.Seek(0,
STREAM_SEEK_SET, test));    Result := Output;  except    Output :=
nil;    raise;  end;end;  procedure TForm1.Button1Click(Sender:
TObject);var    img:IGPImage;    g: IGPGraphics;    Ms:TMemoryStream; 
  Stream : IStream;begin   Ms:=TMemoryStream.Create; 
Ms.LoadFromFile('C:\Users\mali.aydin\Desktop\E.emf'); 
Ms.Position:=0;   //In the example, I have uploaded a file to the
Memory Stream object.  //If you want, you can directly load the stream
object that you read from the database into the memory stream
object.     Stream:=MemoryStreamToIStream(ms);   img :=
TGPImage.Create(stream); 
g:=TGPGraphics.Create(Image1.Canvas.Handle);  g.SetPageUnit
(UnitPixel);  g.DrawImage(img,0,0,Image1.Width,Image1.Height);end;

----------------------------------------------------------------------
Nick00 · 2023-05-03 02:56

Thanks, it works. I wonder why the TMemoryStream->IStream conversion
does not work through the TStreamAdapter...

----------------------------------------------------------------------
loaded · 2023-05-03 04:58

Quote from: Nick00 on May 03, 2023, 04:56:18 amThanks, it works. I
wonder why the TMemoryStream->IStream conversion does not work through
the TStreamAdapter...

First, we can save the streams to the file and check their content.
If the contents are equal, the source of the problem is likely to be
in the position information of the stream.

----------------------------------------------------------------------
marcov · 2023-05-03 07:17

Some fields written with tdbimage also have a small record with info
before the image.

Another thing, is this 32 or 64-bit? It might be simply GDI headers
being untested for 64-bit ?

----------------------------------------------------------------------
Jurassic Pork · 2023-05-03 07:35

Hello,
Quote from: marcov on May 03, 2023, 09:17:25 amSome fields written
with tdbimage also have a small record with info before the image.
The small record is the Extension, have a look to this post to disable
it.
Friendly, J.P

----------------------------------------------------------------------
Nick00 · 2023-05-04 02:36

Saving the stream to a file works. Before saving to a file, I specify
a zero position and before transferring the stream to the
TSreamAdapter, the position is zero.
Initially, the project was written in Delphi 7 and my version with
TSreamAdapter works there without any problems. On Lazarus (32-bit
application) I get an exception.
The images are stored in the database and they were loaded there a
long time ago through the IBExpert utility.
I wonder why the identical code for creating TGPImage from a blob
works in Delphi, but does not work in Lazarus with the same GDI+
library.

----------------------------------------------------------------------
loaded · 2023-05-04 05:14

Quote from: Nick00 on May 04, 2023, 04:36:13 amSaving the stream to a
file works. Before saving to a file, I specify a zero position and
before transferring the stream to the TSreamAdapter, the position is
zero.
Initially, the project was written in Delphi 7 and my version with
TSreamAdapter works there without any problems. On Lazarus (32-bit
application) I get an exception.
The images are stored in the database and they were loaded there a
long time ago through the IBExpert utility.
I wonder why the identical code for creating TGPImage from a blob
works in Delphi, but does not work in Lazarus with the same GDI+
library.

Because of your insistence on the use of TStreamAdapter, I immediately
gave it a try.
I didn't encounter any problems either. The result is very successful 

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
GdiPlus,Activex,Comobj; procedure TForm1.Button1Click(Sender:
TObject);var    img:IGPImage;    g: IGPGraphics;    Ms:TMemoryStream; 
  Stream : IStream;    Adapter:TStreamAdapter;begin 
Ms:=TMemoryStream.Create; 
Ms.LoadFromFile('C:\Users\mali.aydin\Desktop\Emf\emf.emf'); 
Ms.Position:=0;   Adapter:=TStreamAdapter.Create(ms);  Stream :=
Adapter as IStream;   img := TGPImage.Create(stream); 
g:=TGPGraphics.Create(Image1.Canvas.Handle);  g.SetPageUnit
(UnitPixel);  g.DrawImage(img,0,0,Image1.Width,Image1.Height);end;

----------------------------------------------------------------------
Jurassic Pork · 2023-05-04 05:50

Hello,
Quote from: Nick00 on May 04, 2023, 04:36:13 amI wonder why the
identical code for creating TGPImage from a blob works in Delphi, but
does not work in Lazarus with the same GDI+ library.
What is your database ? are you using the same database for delphi and
lazarus ? Can you compare what you read from blob database in delphi
and lazarus (bytes) ?
Friendly, J.P

----------------------------------------------------------------------
Nick00 · 2023-05-04 06:51

Quote from: loaded on May 04, 2023, 07:14:49 amQuote from: Nick00 on
May 04, 2023, 04:36:13 amSaving the stream to a file works. Before
saving to a file, I specify a zero position and before transferring
the stream to the TSreamAdapter, the position is zero.
Initially, the project was written in Delphi 7 and my version with
TSreamAdapter works there without any problems. On Lazarus (32-bit
application) I get an exception.
The images are stored in the database and they were loaded there a
long time ago through the IBExpert utility.
I wonder why the identical code for creating TGPImage from a blob
works in Delphi, but does not work in Lazarus with the same GDI+
library.

Because of your insistence on the use of TStreamAdapter, I immediately
gave it a try.
I didn't encounter any problems either. The result is very successful 

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
GdiPlus,Activex,Comobj; procedure TForm1.Button1Click(Sender:
TObject);var    img:IGPImage;    g: IGPGraphics;    Ms:TMemoryStream; 
  Stream : IStream;    Adapter:TStreamAdapter;begin 
Ms:=TMemoryStream.Create; 
Ms.LoadFromFile('C:\Users\mali.aydin\Desktop\Emf\emf.emf'); 
Ms.Position:=0;   Adapter:=TStreamAdapter.Create(ms);  Stream :=
Adapter as IStream;   img := TGPImage.Create(stream); 
g:=TGPGraphics.Create(Image1.Canvas.Handle);  g.SetPageUnit
(UnitPixel);  g.DrawImage(img,0,0,Image1.Width,Image1.Height);end;
Your code doesn't work with my image. I thought that the problem is in
my image, but the same code works without problems in Delphi 7 with my
image

----------------------------------------------------------------------
loaded · 2023-05-04 06:53

Can you upload a sample image?

----------------------------------------------------------------------
Nick00 · 2023-05-04 06:56

Change the extension to emf.

----------------------------------------------------------------------
loaded · 2023-05-04 10:38

When I save the stream objects it creates in its two methods in a
file, they both have the same content. When I reset the starting
positions, the result is still the same. I think it's an interesting
situation.
There is probably information that the stream object created by the
Adapter class has or does not have, other than the context data.
In the future, I will investigate this issue in depth. I have
different trials in mind, but that's all I've got at the moment.
I would be glad if experts on the subject give their opinion.

----------------------------------------------------------------------
marcov · 2023-05-04 10:56

I also want to have a look in time. Can sb create a bugreport with
image, code and link to gdiplus units?

----------------------------------------------------------------------
loaded · 2023-05-05 06:50

I don't know why, but some issues are stuck in my head. This is one of
them, the opinion that I have reached from the research I have done;

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 procedure
TForm1.ButtonAPClick(Sender: TObject);var    img:IGPImage;    g:
IGPGraphics;    Ms:TMemoryStream;    Adapter:TStreamAdapter;   
EmfStream :IStream;    test:Qword;begin  Ms:=TMemoryStream.Create; 
Ms.LoadFromFile(efp);  Ms.Position:=0;  
Adapter:=TStreamAdapter.Create(ms);   EmfStream:=Adapter as IStream;
// Not the adapter class, the conversion metedo here is doing the
wrong thing.   img := TGPImage.Create(EmfStream); 
g:=TGPGraphics.Create(Image1.Canvas.Handle);  g.SetPageUnit
(UnitPixel);  g.DrawImage(img,0,0,Image1.Width,Image1.Height);end; 
If we make the above "EmfStream:=Adapter as IStream;" method
ourselves. We can see that the problem is fixed.

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 procedure
TForm1.ButtonAPClick(Sender: TObject);    function
AdapterStreamtoIStream(const AStream: TStream): IStream;    var     
Output: IStream;      MemoryPointer: Pointer;      test:Qword;     
begin        try          GetMem(MemoryPointer, AStream.Size);       
 try            AStream.ReadBuffer(MemoryPointer^, AStream.Size);    
    except            FreeMem(MemoryPointer);            raise;      
  end;        finally        end;         CreateStreamOnHGlobal(0,
True, Output);        try          Output.Write(MemoryPointer,
AStream.Size, nil);          Output.Seek(0, STREAM_SEEK_SET, test);  
      Result := Output;        except          Output := nil;        
raise;        end;    end;var    img:IGPImage;    g: IGPGraphics;   
Ms:TMemoryStream;    Adapter:TStreamAdapter;    EmfStream :IStream;  
test:Qword;begin  Ms:=TMemoryStream.Create;  Ms.LoadFromFile(efp); 
Ms.Position:=0;   Adapter:=TStreamAdapter.Create(ms);  
EmfStream:=AdapterStreamtoIStream(Adapter.Stream);  //This code gives
the impression that the adapter class is working correctly.   img :=
TGPImage.Create(EmfStream); 
g:=TGPGraphics.Create(Image1.Canvas.Handle);  g.SetPageUnit
(UnitPixel);  g.DrawImage(img,0,0,Image1.Width,Image1.Height);end; 
This is my last post on the subject.