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Reusing Images in ReportBuilder Reports While Exporting to PDF

Does your ReportBuilder report contain logos in the page header / footer that repeat on every page? Do you wish to store only a single copy of the logo when you export the report to PDF and greatly reduce your PDF file size? This article will illustrate how to achieve this using Gnostice eDocEngine VCL along with Gnostice ReportBuilder Export Interface.

By S. Vikram & S. Bhamini

It is common to have the company logo in a report’s header/footer section. However, when such reports are exported to PDF, by default, a separate copy of the same image is stored for each page in the report, unnecessarily adding to the size of the PDF document. If you are using ReportBuilder for generating your reports, then you can use Gnostice eDocEngine to export the report to PDF and optimize the process to store only one copy of the image in the PDF file and reuse it on each page of the report as required.

eDocEngine provides features to refer to images being inserted into the document and later reuse them with the help of the reference. These features are exposed through OnEncodeGraphic and OnEncodeGraphicDone events of gtRBExportInterface component. Reusing common images can greatly reduce the file size of the PDF document. Our article will demonstrate how to do this, using an example report.

The following example uses a ReportBuilder report with three images in the page header and connects to ‘Biolife’ table of the ‘DBDEMOS’ database (which comes along with Delphi).

Add gtPDFEngine and gtRBExportInterface components to your project, for exporting the reports to PDF

• Drop the gtPDFEngine and gtRBExportInterface components on the main form of the project from the ‘eDocEngine’ and ‘eDocEngine Additional’ palettes respectively, in Delphi.
• Connect the Engine property of the gtRBExportInterface to gtPDFEngine.
• Set the properties of gtPDFEngine if required.

Add code to handle the images

• Add member fields to the main class (usually the application Form).

  // Resource-Index of the current image being encoded
  FImgIndex: array of Integer;
  
  // Array-Index of the current image being encoded
  FImgNumber: Integer;
  
  // Total Number of Images used as resources
  FImgCnt: Integer;
  

• Initialize the member fields depending on the number of images in report page header.

  // Initial settings
  FImgCnt := 3;
  SetLength(FImgIndex, FImgCnt);
  
  for LI := Low(FImgIndex) to High(FImgIndex) do
    FImgIndex[LI] := -1;
  
  FImgNumber := 0;
  

• Handle the OnEncodeGraphic event of gtRBExportInterface to write the below code.

  procedure TForm1.gtRBExportInterface1EncodeGraphic(
     AObject: TObject;
     var UniqueImage: Boolean;
     var ReuseImageIndex: Integer);
  begin
    // Process images as resources
    UniqueImage := False;
    // Assign image resource index
    ReuseImageIndex := FImgIndex[FImgNumber];
  end;
  

• Handle the OnEncodeGraphicDone event of the gtRBExportInterface.

  procedure TForm1.gtRBExportInterface1EncodeGraphicDone(
    AObject: TObject;
    ObjectImageIndex: Integer);
  begin
    // Store the image index for the first time only
    if (FImgIndex[FImgNumber] = -1) then
      FImgIndex[FImgNumber] := ObjectImageIndex;
    // Cyclicaly increment array index
    FImgNumber := (FImgNumber + 1) mod FImgCnt;
  end;
  

Add code to export the ReportBuilder report

• Write code to export the report to PDF.

  gtPDFEngine1.FileName := 'Sample';
  gtRBExportInterface1.RenderDocument(ppReport1);
  

--- oO0Oo ---

Downloads:

• SampleOutputPDF.zip: - PDF generated with one of the reports in the demo
• SampleProject.zip: Sample project illustrating the above article
• ExecutableDemo.zip: An executable demo