Replacing StretchDIBits with GDI+ (while drawing an Image to Printer's canvas) - delphi

Question

My application is developed in Delphi 6. This is a resource intesive application due to background processing and large volume of data (It consumes around 60MB - 120MB of physical memory). One of the functionality of this application is to create barcode images and print them. If user keeps on generating the Barcodes, then at least One out of Ten Barcode has missing lines in it.
I was able to resolve this issue using TExcellenImagePrinter component. But, it diminished the performance a lot. This resolution was rejected by my client and hence, now I am trying to replace the WinAPI StretchDIBits call with GDI+.
The original source code is as following:
procedure PrintBitmap(ARect:TRect; Bitmap:TBitmap);
var
Info: PBitmapInfo;
InfoSize: dword{Integer};
Image: Pointer;
ImageSize: dword{ integer};
iWidth,iHeight :integer;
iReturn : integer ;
begin
GetDIBSizes(Bitmap.handle,InfoSize,ImageSize);
if (LoadDIBFromTBitmap(Bitmap,Pointer(Info),Image,iWidth,iHeight)) then
begin
SetStretchBltMode(Printer.Canvas.handle,STRETCH_HALFTONE);
SetBrushOrgEx(Printer.Canvas.handle, 0, 0, NIL);
iReturn := StretchDIBits(Printer.Canvas.Handle, ARect.Left, ARect.Top,
ARect.Right - ARect.Left, ARect.Bottom - ARect.Top,
0, 0, Info^.bmiHeader.biWidth,
Info^.bmiHeader.biHeight, Image, Info^,DIB_RGB_COLORS, SRCCOPY);
end;
FreeMemEx(Info);
FreeMemEx(Image);
end;
I got the GDI+ header from the (http://www.progdigy.com/?page_id=7) as suggested by Joe in embarcadero forums (https://forums.embarcadero.com/thread.jspa?messageID=471501#471501).
I have modified my source code as following :
Created an object of TGPGraphics class and assigned the printer's handle to it.
gp := TGPGraphics.Create(Printer.Canvas.Handle);
Created an onject of TGPBitmap class and assigned the barcode image to it.
bmp := TGPBitmap.Create(Info^,Image);
Info is TBitmapInfo and Image is an pointer.
Assigned the Printer's dimension to the an instance rect of TGPRect record
Called the DrawImage function :
gp.DrawImage(bmp,rect);
But, after making these changes, empty image is shown in the printer's output.
Can you point out if I have missed something or my implementation is wrong.
Can you provide any pointers regarding this?

Answer 1

I have found the following code demonstrating creation of compatible bitmap (DBB) from a dib.
That should work for you. Probably it could be written better but all in all it just works ... at least for me..
procedure PRPrintBitmapOnCanvas(Canvas: TMetafileCanvas; Bitmap: TBitmap; posLeft, posTop: Integer);
var
lpbmih: TBitmapInfoHeader;
lpbmi: TBitmapInfo;
aBitmap: HBITMAP;
aDC: LongWord;
begin
Fillchar(lpbmih, SizeOf(lpbmih), 0);
lpbmih.biSize := SizeOf(lpbmih);
lpbmih.biWidth := bitmap.width;
lpbmih.biHeight := bitmap.height;
lpbmih.biPlanes := 1;
lpbmih.biBitCount := 32;
lpbmih.biCompression := BI_RGB;
Fillchar(lpbmi, SizeOf(lpbmi), 0);
lpbmi.bmiHeader.biSize := SizeOf(lpbmi.bmiHeader);
lpbmi.bmiHeader.biPlanes := 1;
lpbmi.bmiHeader.biBitCount := 32;
lpbmi.bmiHeader.biCompression := BI_RGB;
aBitmap := CreateDIBitmap(Canvas.Handle, lpbmih, 0, nil, lpbmi, DIB_RGB_COLORS);
if aBitmap = 0 then RaiseLastOSError;
try
aDC := CreateCompatibleDC(Canvas.Handle);
SelectObject(aDC, aBitmap);
BitBlt(aDC, 0, 0, bitmap.Width, bitmap.Height, bitmap.Canvas.Handle, 0, 0, SRCCOPY);
BitBlt(canvas.handle, posLeft, posTop, bitmap.Width, bitmap.Height, aDC, 0, 0, SRCCOPY);
DeleteDC(aDC);
finally
DeleteObject(aBitmap)
end;
end;