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Table of contents

PDF Handling

PDFs are widely used in many and various industries, and presently are the only non-image file type that DWT supports. In this next section, we will address all the input and output operations that allow the user to properly handle PDF files.

Environment

Including the PDF addon

To include the PDF addon, simply add a reference to the corresponding JavaScript file, included in the resources folder.

<script src="Resources/addon/dynamsoft.webtwain.addon.pdf.js"></script>

If you are using the dwt package, the pdf addon is already included in the main JavaScript file ( dynamsoft.webtwain.min.js or dynamsoft.webtwain.min.mjs ) which means you can skip this step.

Input

Open an image-only PDF file

When loading in a PDF file, DWT tries to extract images from that file, which is why the SDK can handle image-based PDF documents by default.

Open a searchable PDF file

However, most existing PDF files contain much more than just images. For image-and-text PDF files, we need to make use of the PDF Rasterizer (PDFR for short), the main component of the PDF addon.

How PDFR works: As the name suggests, PDFR rasterizes a PDF file page by page much like a scanner. You set a resolution, and you get the resulting images in that resolution after the rasterization.

The following code shows the basic usage

var onSuccess = function() {
    console.log("Loaded a file successfully!");
};
var onFailure = function(errorCode, errorString) {
    console.log(errorString);
};
DWObject.IfShowFileDialog = true;
// PDF Addon is used here to ensure text-based PDF support
DWObject.Addon.PDF.SetResolution(300);
DWObject.Addon.PDF.SetConvertMode(Dynamsoft.DWT.EnumDWT_ConvertMode.CM_RENDERALL);
DWObject.LoadImageEx("", Dynamsoft.DWT.EnumDWT_ImageType.IT_ALL, onSuccess, onFailure);

The method SetConvertMode() decides how PDFR works and SetResolution() specifies the resolution. These two methods configure PDFR to detect and, if necessary, rasterize any PDF file that comes thereafter.

Sample code

See full sample here.

Other methods

Output as PDF

Save images as image-based PDFs

DWT can output one or multiple images in the buffer as image-based PDF file(s). This feature is built into the core module, and no addon is required as was covered in the output section.

PDF save settings

However, some advanced features are only possible with the help of the PDF addon. At present, that means configuring the resulting file(s) with the API Write.Setup() as shown below

DWObject.Addon.PDF.Write.Setup({
    author: "Dynamsoft-Support-Team",
    compression: Dynamsoft.DWT.EnumDWT_PDFCompressionType.PDF_JP2000,
    pageType:Dynamsoft.DWT.EnumPDF_Page_A4,
    creator: "DWT",
    creationDate: "D:20200930",
    keyWords: "TWAIN, DWT, Dynamsoft",
    modifiedDate: "D:20200930",
    producer: "Dynamsoft Corporation",
    subject: "Demoing File",
    title: "Sample PDF Made by DWT",
    version: 1.5,
    quality: 80
});
DWObject.IfShowFileDialog = true;
DWObject.SaveAllAsPDF(' ', function() {}, function() {})

Note: Only the core module license is required to use this method.

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