| T O P I C R E V I E W |
| Reiner |
Posted - Sep 26 2018 : 16:09:03
Hi,
we have just put the TIEBitmap and TImageEnIO into the kernel of our printing application to handle multipage tiff sources. In principle everything works as expected ... but randomly a few pages come out as blanc pages.
We could locate the issue as a possible timing problem while using the RenderToCanvas() method. Here the results, focussing on the central methods:
Sequence (1) - Straight forward
ietifbmp->RenderToCanvas(PrnBmp->Canvas,L,T,W,H,rfLanczos3,0,clWhite);
Printer()->Canvas->StretchDraw(Printer()->Canvas->ClipRect,PrnBmp);
===> blanc pages are printed randomly (about one of 10)
Sequence (2)- Inserting a delay
ietifbmp->RenderToCanvas(PrnBmp->Canvas,L,T,W,H,rfLanczos3,0,clWhite);
DelayLoop(500 ms) // containing Application->ProcessMessages()
Printer()->Canvas->StretchDraw(Printer()->Canvas->ClipRect, PrnBmp);
===> all pages are printed, anytime
My assumption: The RenderToCanvas() method seems to work asynchronly, i.e. it returns before the target bitmap is completed.
Is there any solution like an event or a state value that can inform us about the rendering process state.
Thank you!
Reiner |
| 4 L A T E S T R E P L I E S (Newest First) |
| xequte |
Posted - Sep 29 2018 : 22:43:03
Hi Reiner
Good to hear you have found a working solution.
Nigel
Xequte Software
www.imageen.com
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| Reiner |
Posted - Sep 29 2018 : 14:41:43
Hi again Nigel,
it took me a while, because our test program did not show any problems with the multipage-tiff-printing.
//---------------------------------------------------------------------------
#include <vcl.h>
#pragma hdrstop
#include "Unit1.h"
//---------------------------------------------------------------------------
#pragma package(smart_init)
#pragma link "hyiedefs"
#pragma link "hyieutils"
#pragma link "iesettings"
#pragma link "iexLayers"
#pragma link "iexRulers"
#pragma link "ieopensavedlg"
#pragma link "iexBitmaps"
#pragma link "ieview"
#pragma link "imageenio"
#pragma link "imageenview"
#pragma resource "*.dfm"
TForm1 *Form1;
TPrinter *PRN;
//---------------------------------------------------------------------------
__fastcall TForm1::TForm1(TComponent* Owner): TForm(Owner)
//---------------------------------------------------------------------------
{
}
//---------------------------------------------------------------------------
void __fastcall TForm1::Button0Click(TObject *Sender)
//---------------------------------------------------------------------------
{
TIETIFFHandler *tiffs=new TIETIFFHandler();
TMemoryStream *tmp =new TMemoryStream();
TIEBitmap *iebmp=new TIEBitmap();
TImageEnIO *IO =new TImageEnIO(iebmp);
TBitmap *bmp =new TBitmap;
bmp->Width = 2479;
bmp->Height = 3508;
PRN=Printer();
OpenFileDlg->Execute();
if(OpenFileDlg->FileNameW!="")
{
PRN->BeginDoc();
PRN->Canvas->CopyMode=cmSrcCopy;
tiffs->ReadFile(OpenFileDlg->FileNameW);
int pages=tiffs->GetPagesCount();
Button0->Caption=IntToStr(pages)+" Pages";
for(int i=0; i<pages; i++) // print all pages of the tif-file
{
tmp->Position=0; tiffs->WriteStream(tmp,i);
tmp->Position=0; IO->LoadFromStreamTIFF(tmp);
// render to intermediate bitmap (this step is not really necessary)
iebmp->RenderToCanvas(bmp->Canvas,0,0,2479,3508,rfFastLinear,0,clWhite);
PRN->Canvas->StretchDraw(PRN->Canvas->ClipRect,bmp);
if(i<pages-1)PRN->NewPage();
// IM->Picture->Bitmap->Assign(bmp); // TImage control on Form1
Button0->Caption=IntToStr(pages)+" Pages printed";
}
PRN->EndDoc();
}
delete bmp;
delete IO;
delete iebmp;
delete tmp;
delete tiffs;
}
//---------------------------------------------------------------------------
In my final application the rendering and printing portion shown above is located within a Windows service class. Probably here we are facing the asynchronous effects providing us blanc pages. Here your assumption regarding the Printer->Canvas behavior hits the mark.
After a few more hours of try&error I now have noticed, that if we just add the following 1-dot-Draw function ahead the main StretchDraw(), the blanc pages disappear:
PRN->Canvas->Draw(0,0,1_dot_bmp); // added line
PRN->Canvas->StretchDraw(PRN->Canvas->ClipRect,bmp);
I admit that this does not get us to the root cause but it gets our application working stable up to now.
Thank you again
Reiner |
| Reiner |
Posted - Sep 28 2018 : 01:57:02
Hi Nigel,
Thanks a lot for your prompt reply.
This is already a valuable information.
I will prepare a little test program for further research and come back to this thread as soon as possible.
Reiner |
| xequte |
Posted - Sep 27 2018 : 15:24:02
Hi Reiner
RenderToCanvas isn't asynchronous, but is it possible that Printer->Canvas work asynchronously (using Windows messages, which explains the ProcessMessages() calls).
Is PrnBmp a TIEBitmap or TBitmap?
Unfortunately we cannot reproduce the error here. Are you able to create a simple test application that shows the issue?
Nigel
Xequte Software
www.imageen.com
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