How to Scan Documents to PDF Files from Browsers

Portable Document Format (PDF) is a file format developed by Adobe to present documents in a manner independent of application software, hardware, and operating systems.1

The basic types of content in a PDF are:

  • Typeset text stored as content streams;
  • Vector graphics for illustrations and designs that consist of shapes and lines;
  • Raster graphics for photographs and other types of images
  • Multimedia objects in the document.

PDF is suitable as the container of the images of scanned documents (mainly raster graphics). We can also modify it in the following aspects for different needs:

  • Turn the PDF file into a searchable one using OCR.
  • Add encryption.
  • Add metadata like the author, title and description.
  • Add annotations.

Dynamic Web TWAIN has good support for the PDF format. In this article, we are going to create a demo web app to illustrate how to use it to scan documents and save them as a PDF file from browsers.

Getting Started With Dynamic Web TWAIN

Dynamic Web TWAIN  

Demo Web App which Scans Documents from the Camera to PDF Files

Let’s do this in steps.

Preparation

  1. Download and install Dynamic Web TWAIN from here.
  2. Create a new folder for storing the web pages and put the Resources folder of Dynamic Web TWAIN in that folder.

  3. Create a camera.html which scans documents using a camera. Here is its code:

    <!DOCTYPE html>
<html>
<head>
  <title>Scan to PDF</title>
  <meta name="viewport" content="width=device-width,initial-scale=1.0,maximum-scale=1.0,user-scalable=0" />
  <script type="text/javascript" src="Resources/dynamsoft.webtwain.initiate.js"></script>
  <script type="text/javascript" src="Resources/dynamsoft.webtwain.config.js"></script>
  <script type="text/javascript" src="Resources/addon/dynamsoft.webtwain.addon.pdf.js"></script>
  <script type="text/javascript" src="Resources/addon/dynamsoft.webtwain.addon.camera.js"></script>
</head>
<body>
  <h2>Input</h2>
  <div class="panel">
    <input type="button" value="Load Images" onclick="LoadImages();" />
    <input type="button" value="Camera" onclick="StartCamera();" />
    <input type="button" value="Edit" onclick="StartDocumentEditor();" />
  </div>
  <div id="dwtcontrolContainer" style="width: 350px; height: 380px;"></div>
  <script type="text/javascript">
    Dynamsoft.DWT.RegisterEvent('OnWebTwainReady', Dynamsoft_OnReady); // Register OnWebTwainReady event. This event fires as soon as Dynamic Web TWAIN is initialized and ready to be used
    Dynamsoft.DWT.UseLocalService = false;
    let DWObject;

    function Dynamsoft_OnReady() {
      DWObject = Dynamsoft.DWT.GetWebTwain('dwtcontrolContainer'); // Get the Dynamic Web TWAIN object that is embeded in the div with id 'dwtcontrolContainer'
      DWObject.SetViewMode(2, 2);
    }
       
    function LoadImages(){
      if (DWObject) {
        DWObject.IfShowFileDialog = true; // Open the system's file dialog to load image
        DWObject.LoadImageEx("", Dynamsoft.DWT.EnumDWT_ImageType.IT_ALL);
      }
    }
       
    function StartCamera(){
      if (DWObject) {
        DWObject.Addon.Camera.scanDocument().then( //open the camera to scan documents
          function(){
            console.log("OK");
          }, 
          function(error){
            console.log(error.message);
          }
        );
      }
    }
       
    function StartDocumentEditor() {
      if (DWObject) {
        let documentEditor = DWObject.Viewer.createDocumentEditor();
        documentEditor.show();
      }
    }
  </script>
</body>
</html>

    Screenshot:

    DWT PDF Demo Input

Save the Documents as a PDF File

Next, we are going to add a save button to save documents as a PDF file.

HTML:

<input type="button" value="Save as PDF" onclick="Save();" />

JavaScript:

function Save(){
  if (DWObject) {
    let OnSuccess = function () {
      alert("Success");
    };
    let OnFailure = function () {
      alert("Fail");
    };
    
    DWObject.SaveAllAsPDF("DynamicWebTWAIN.pdf", OnSuccess, OnFailure);
  }
}

Customize the PDF Output Settings

We can use the Write.Setup function of the PDF addon to customize the settings of the PDF output.

  1. Modify the metadata.

    let pdfSaveSettings = { 
            author: "Dynamsoft", 
            creator: "DWT", 
            creationDate: "", 
            keyWords: "", 
            modifiedDate: "", 
            producer: "Dynamsoft Corporation", 
            subject: "", 
            title: "", 
            version: 1.5};
DWObject.Addon.PDF.Write.Setup(pdfSaveSettings);

  2. Specify a page type.

    Dynamic Web TWAIN supports the following page types.

    Label Value
    Page_Default 0
    Page_Custom 1
    Page_A4 2
    Page_A4_Reverse 3
    Page_A3 4
    Page_A3_Reverse 5
    Page_Letter 6
    Page_Letter_Reverse 7
    Page_Legal 8
    Page_Legal_Reverse 9

    Specifying a page type is useful for saving document images captured using a camera to unify the page size.

    let pdfSaveSettings = { pageType: 2 }; // pass 2 to set it as A4
DWObject.Addon.PDF.Write.Setup(pdfSaveSettings);

  3. Specify a compression type.

    Dynamic Web TWAIN supports the following compression algorithms.

    Label Value
    PDF_AUTO 0
    PDF_FAX4 2
    PDF_LZW 3
    PDF_JPEG 5
    PDF_JP2000 6
    PDF_JBIG2 7

    For example, we can use JPEG as the compression type. We can also set the output quality by modifying the quality value.

    let pdfSaveSettings = { 
               pageType: Dynamsoft.DWT.EnumDWT_PDFCompressionType.PDF_JPEG,
               quality: DWObject.JPEGQuality };
DWObject.Addon.PDF.Write.Setup(pdfSaveSettings);

    When set to PDF_AUTO, Dynamic Web TWAIN will automatically choose the suitable compression type for each image.

    • For 1 Bit images, if the PDF version is over 1.4, use JBIG2 encoding, otherwise, use FAX4 (CCITT Group 4 Fax).
    • For 8 Bit images, if the image is grayscale, use JPEG encoding, otherwise, use LZW (Lempel-Ziv-Welch).
    • For 24 and 32 Bit images, use JPEG encoding.

Source Code

Check out the source code of the samples to have a try.

References

  1. https://en.wikipedia.org/wiki/PDF ↩