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Home » Newsletter » March 2007

By Mohammed Najeemudheen & Shine Babu

When images are used as hyperlinks, it adds a small but significant touch of interactivity to PDF documents. In this tip, we will show you how to add a set of URLs to images in a PDF document.

Here, we assume that each page in the document have the same set of images and that we need to add the URLs in the order we find the images in each page.

The code for this is pretty simple. First, we put the URLs (URIs) in a list. Then, we load each page in the document. Next, we identify where the images are located on the pages. We then create a link annotation for each image and set the annotation's rectangle to the dimensions of the image. Finally, each link annotation is set to a URL that corresponds to the order of the image in the page.

var
  LinkAnnot : TgtPDFLinkAnnotation;
  URI : TgtPDFURIAction;
  LImageList : TgtPDFPageElementList;
  LStringLinks : TStringList;
  StrLink : String;
  LI,LJ,LK : Integer;
  LLeft, LRight, LBottom, LTop,LWidth, LHeight: Double;
begin
  LStringLinks := TStringList.Create;
  PDFDoc.LoadFromFile('Input.pdf');
  PDFDoc.OpenAfterSave := True;
 
  // Creates a link annotation object
  LinkAnnot := TgtPDFLinkAnnotation.Create;
  LinkAnnot.Contents := 'PDFtoolkit';

  // Creates a URI object
  URI := TgtPDFURIAction.Create ;

  // Sets the properties of the link annotation
  LinkAnnot.BackgroundColor := clBlue;
  LinkAnnot.AnnotTitle := 'LinkAnnotion';
  LinkAnnot.Name := 'Link1';
  LinkAnnot.BorderWidth := 0;

  // Creates a list of URIs
  LStringLinks.Add('www.gmail.com');
  LStringLinks.Add('www.adobe.com');
  LStringLinks.Add('www.rediffmail.com');

 // for each page in the document ...
 for LJ:= 1 to PDFDoc.PageCount do
  begin
    // Creates a list of image items in a given page
    LImageList := 
          PDFDoc.GetPageElements(LJ,[etImage],muPixels);
    LK := 0;
    // for each image in the list ...
    for LI:= 0 to LImageList.Count - 1 do
    begin
      if LK < LStringLinks.Count then
      begin
        // Sets the URI property of the link annotation 
        // action to a corresponding URL from the list
        URI.URI := LStringLinks[LK];
        LinkAnnot.Action :=  URI;

        // Obtains the width and height of image
        LWidth := TgtPDFImageElement(
           LImageList.Items[LI]).XCoordinateScalingFactor;
        LHeight := TgtPDFImageElement(
           LImageList.Items[LI]).YCoordinateScalingFactor;

        LLeft := LImageList.Items[LI].XCordOrigin;
        LTop := LImageList.Items[LI].YCordOrigin + LHeight ;
        LRight := LImageList.Items[LI].XCordOrigin +LWidth ;
        LBottom := LImageList.Items[LI].YCordOrigin;

        // Specifies the annotation rectangle
        LinkAnnot.SetBounds(LLeft, LTop, LRight, LBottom);

        // Adds the link annotation on the image
        PDFDoc.InsertAnnotation(LinkAnnot,LJ);
        Inc(LK);
          if LK = LStringLinks.Count then
            LK := 0;
      end;
    end;
  end;
  // Saves the PDF document
  PDFDoc.SaveToFile('LinkAnnot.pdf');