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.jsordynamsoft.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,
PDFRrasterizes 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
-
GetConvertMode(): This method returns the current convert mode. -
SetPassword(): This method sets a password which is used to open encrypted PDF file(s).
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.
Yes
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