Question

I would like to convert a TBitMap to a PBitMap in KOL.

I tried this but I get a black picture as an output:

function TbitMapToPBitMap (bitmap : TBitMap) : PbitMap;
begin
 result := NIL;
 if Assigned(bitmap) then begin
  result := NewBitmap(bitmap.Width, bitmap.Height);
  result.Draw(bitmap.Canvas.Handle, bitmap.Width, bitmap.Height);
 end;
end;

Any idea what’s wrong with it? I am using Delphi7.

Thank you for your help.

EDIT: New CODE:

function TbitMapToPBitMap (const src : TBitMap; var dest : PBitMap) : Bool; 
begin
 result := false;
 if (( Assigned(src) ) and ( Assigned (dest) )) then begin
 dest.Draw(src.Canvas.Handle, src.Width, src.Height);
 result := true;
 end;
end;

procedure TForm1.Button1Click(Sender: TObject);
var
 TBitMapTest : TBitMap;
 PBitMapTest : PBitMap;
begin
 TBitMapTest := TBitMap.Create;
 TBitMapTest.LoadFromFile ('C:\test.bmp');
 PBitMapTest := NewBitMap (TBitMapTest.Width, TBitMapTest.Height);
 TbitMapToPBitMap (TBitMapTest, PBitMapTest);
 PBitMapTest.SaveToFile ('C:\test2.bmp');
 PBitMapTest.Free;
 TBitMapTest.Free;
end;

Answer 1

To answer your question why are your target images black; it’s because you were drawing those target images to source and black they were because the NewBitmap initializes images to black.

How to copy or convert if you want a TBitmap to KOL PBitmap I found only one way (maybe I missed such function in KOL, but even if so, the method used in the following code is very efficient). You can use the Windows GDI function for bit-block transfer, the BitBlt, which just copies the specified area from one canvas to another.

The following code, when you click on the button creates the VCL and KOL bitmap instances, loads the image to a VCL bitmap, call the VCL to KOL bitmap copy function and if this function succeed, draw the KOL bitmap to the form canvas and free both bitmap instances:

uses
  Graphics, KOL;

function CopyBitmapToKOL(Source: Graphics.TBitmap; Target: PBitmap): Boolean;
begin
  Result := False;
  if Assigned(Source) and Assigned(Target) then
  begin
    Result := BitBlt(Target.Canvas.Handle, 0, 0, Source.Width, Source.Height,
      Source.Canvas.Handle, 0, 0, SRCCOPY);
  end;
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  KOLBitmap: PBitmap;
  VCLBitmap: Graphics.TBitmap;
begin
  VCLBitmap := Graphics.TBitmap.Create;
  try
    VCLBitmap.LoadFromFile('d:\CGLIn.bmp');
    KOLBitmap := NewBitmap(VCLBitmap.Width, VCLBitmap.Height);
    try
      if CopyBitmapToKOL(VCLBitmap, KOLBitmap) then
        KOLBitmap.Draw(Canvas.Handle, 0, 0);
    finally
      KOLBitmap.Free;
    end;
  finally
    VCLBitmap.Free;
  end;
end;