BeginUpdate Method

Summary

Begins a process to update the elements (nodes) of an SVG document.

Syntax

Objective-C

C++/CLI

Java

Python

public void BeginUpdate()

- (void)beginUpdate;

public void beginUpdate()

public: 
void BeginUpdate();

def BeginUpdate(self):

Remarks

The user can modify the elements of an SVG document using EnumerateElements and update the node's elements or attributes.

After modifying the values of an SVG document using SvgNodeHandle, it may be necessary to re-calculate the document flat, render optimization and bounding rectangles (refer to SVG Size, Bounds and Flat more information). Therefore, it is best to call BeginUpdate before making any updates to the document and to call EndUpdate when finished. The engine will check during EndUpdate whether any internal state values need to be re-calculated and updated as necessary.

BeginUpdate increments an internal counter and EndUpdate decrements it. When the counter reaches 0 again, the document is updated. Therefore, the user can chain calls to BeginUpdate / EndUpdate pair and the update will only occur once at the end.

Example

Java

using Leadtools; 
using Leadtools.Codecs; 
using Leadtools.Drawing; 
using Leadtools.Forms.DocumentWriters; 
using Leadtools.Svg; 
 
using Leadtools.Document.Writer; 
 
private static void SvgDocumentEnumerateElementsExample() 
{ 
   // The source PDF file 
   var sourceFile = $@"{LEAD_VARS.ImagesDir}\Leadtools.pdf"; 
   var beforeSvgFile = $@"{LEAD_VARS.ImagesDir}\Leadtools_before.svg"; 
   var afterSvgFile = $@"{LEAD_VARS.ImagesDir}\Leadtools_after.svg"; 
 
   // Assume this is our Virtual Directory 
   var virtualDirectory = "http://localhost/leadtools_images/svg/resources"; 
   // Assume this phrysical directory maps to the Virtual Directory 
   var physicalDirectory = $@"{LEAD_VARS.ImagesDir}\svg\resources"; 
 
   if (!Directory.Exists(physicalDirectory)) 
      Directory.CreateDirectory(physicalDirectory); 
 
   // Our SVG element enumartion callback 
   SvgEnumerateElementsCallback callback = (SvgDocument document, SvgNodeHandle node, object userData) => 
   { 
      if (node.ElementType == SvgElementType.Image) 
      { 
         // Get the href 
         var href = node.GetAttributeValue("xlink:href"); 
         if (!string.IsNullOrEmpty(href)) 
         { 
            // Parse it as data URI 
            var dataUri = SvgDataUri.Parse(href); 
            // Check if it is a data URI 
            if (dataUri.IsDataUri) 
            { 
               // Yes, create a new file in a virtual directory 
 
               // Show the dataURI properties 
               Console.WriteLine("Replacing data URI"); 
               Console.WriteLine("Format:" + dataUri.ImageFormat); 
               if (dataUri.MediaLength > 0) 
                  Console.WriteLine("Media:" + dataUri.Href.Substring(dataUri.MediaOffset, dataUri.MediaLength)); 
               if (dataUri.CharSetOffset > 0) 
                  Console.WriteLine("CharSet:" + dataUri.Href.Substring(dataUri.CharSetOffset, dataUri.CharSetLength)); 
               else 
                  Console.WriteLine("CharSet: not set"); 
               Console.WriteLine("IsBase64:" + dataUri.IsBase64); 
               Console.WriteLine("ImageFormat:" + dataUri.ImageFormat); 
               var extension = dataUri.Extension; 
               Console.WriteLine("Extension:" + dataUri.Extension); 
 
               // Get a file name 
               var name = Guid.NewGuid().ToString().Replace("-", "") + "." + dataUri.Extension; 
 
               // Save it 
               // Full physical path 
               var filePath = Path.Combine(physicalDirectory, name); 
               dataUri.DecodeToFile(filePath); 
 
               /* Alternatively you can save the data yourself using this code 
               var data = dataUri.Href.Substring(dataUri.ValueOffset, dataUri.ValueLength); 
 
               // Save the data 
               var base64String = dataUri.Href.Substring(dataUri.ValueOffset, dataUri.ValueLength); 
               byte[] rawData = Convert.FromBase64String(base64String); 
 
               // Save it to disk 
               File.WriteAllBytes(filePath, rawData); 
               */ 
 
               // Finally replace the attribute in the image element with the URI 
               var virtualPath = virtualDirectory + "/" + name; 
               node.SetAttributeValue("xlink:href", virtualPath); 
            } 
            else 
            { 
               Console.WriteLine("Does not contain a valid data URI."); 
            } 
         } 
      } 
      return true; 
   }; 
 
   using (var rasterCodecs = new RasterCodecs()) 
   { 
      // Use 300 DPI when loading document images 
      rasterCodecs.Options.RasterizeDocument.Load.Resolution = 300; 
 
      // Load the first page as SVG 
      using (var svg = rasterCodecs.LoadSvg(sourceFile, 1, null) as SvgDocument) 
      { 
         if (!svg.IsFlat) 
            svg.Flat(null); 
         if (!svg.Bounds.IsValid) 
            svg.CalculateBounds(false); 
 
         // Save this SVG to disk, report the size 
         svg.SaveToFile(beforeSvgFile, null); 
         Console.WriteLine("Before unembedding the image, size is " + new FileInfo(beforeSvgFile).Length); 
 
         // Now enumerate the elements to replace each embedded image with a URL 
         // Since we are going to modify the SVG, call BeginUpdate/EndUpdate to speed up the process 
         svg.BeginUpdate(); 
         svg.EnumerateElements(new SvgEnumerateOptions { EnumerateDirection = SvgEnumerateDirection.TopToBottom }, callback, null); 
         svg.EndUpdate(); 
 
         // Save this SVG to disk again, report the size, should be alot smaller since the image are unembedded and stored as external resources 
         svg.SaveToFile(afterSvgFile, null); 
         Console.WriteLine("Before unembedding the image, size is " + new FileInfo(afterSvgFile).Length); 
      } 
   } 
} 
 
static class LEAD_VARS 
{ 
   public const string ImagesDir = @"C:\LEADTOOLS23\Resources\Images"; 
}

 
import java.io.ByteArrayInputStream; 
import java.io.ByteArrayOutputStream; 
import java.io.File; 
import java.io.FileInputStream; 
import java.io.FileOutputStream; 
import java.io.IOException; 
import java.io.ObjectInputStream; 
import java.io.ObjectOutputStream; 
import java.io.PrintStream; 
import java.nio.file.FileVisitOption; 
import java.nio.file.Files; 
import java.nio.file.Path; 
import java.nio.file.Paths; 
import java.util.stream.Stream; 
 
import org.junit.*; 
import org.junit.runner.JUnitCore; 
import org.junit.runner.Result; 
import org.junit.runner.notification.Failure; 
import static org.junit.Assert.*; 
 
import leadtools.*; 
import leadtools.codecs.*; 
import leadtools.document.writer.*; 
import leadtools.svg.*; 
 
 
public void svgDocumentEnumerateElementsExample() { 
   String LEAD_VARS_ImagesDir = "C:\\LEADTOOLS23\\Resources\\Images"; 
   // The source PDF file 
   String srcFilePath = combine(LEAD_VARS_ImagesDir, "Leadtools_pdf.svg"); 
   String beforeSvgFile = combine(LEAD_VARS_ImagesDir, "Leadtools_before.svg"); 
   String afterSvgFile = combine(LEAD_VARS_ImagesDir, "Leadtools_after.svg"); 
 
   // Assume this is our Virtual Directory 
   String virtualDirectory = "http://localhost/leadtools_images/svg/resources"; 
   // Assume this phrysical directory maps to the Virtual Directory 
   String physicalDirectory = combine(LEAD_VARS_ImagesDir, "svg\\resources"); 
 
   if (!new File(physicalDirectory).exists()) 
      new File(physicalDirectory).mkdirs(); 
 
   // Our SVG element enumartion callback 
   SvgEnumerateElementsCallback callback = (SvgDocument document, SvgNodeHandle node, Object userData) -> { 
      if (node.getElementType() == SvgElementType.IMAGE) { 
         // Get the href 
         String href = node.getAttributeValue("xlink:href"); 
         if (!href.isEmpty() || href != null) { 
            // Parse it as data URI 
            SvgDataUri dataUri = SvgDataUri.parse(href); 
            // Check if it is a data URI 
            if (dataUri.isDataUri()) { 
               // Yes, create a new file in a virtual directory 
 
               // Show the dataURI properties 
               System.out.println("Replacing data URI"); 
               System.out.println("Format:" + dataUri.getImageFormat()); 
               if (dataUri.getMediaLength() > 0) 
                  System.out.println( 
                        "Media:" + dataUri.getHref().substring(dataUri.getMediaOffset(), dataUri.getMediaLength())); 
               if (dataUri.getCharSetOffset() > 0) 
                  System.out.println( 
                        "CharSet:" 
                              + dataUri.getHref().substring(dataUri.getCharSetOffset(), dataUri.getCharSetLength())); 
               else 
                  System.out.println("CharSet: not set"); 
 
               System.out.println("IsBase64:" + dataUri.isBase64()); 
               System.out.println("ImageFormat:" + dataUri.getImageFormat()); 
               String extension = dataUri.getExtension(); 
               System.out.println("Extension:" + extension); 
 
               // Get a file name 
               String name = "dstSrcFile" + extension; 
 
               // Save it 
               // Full physical path 
               String filePath = combine(physicalDirectory, name); 
               dataUri.decodeToFile(filePath); 
 
               // Finally replace the attribute in the image element with the URI 
               String virtualPath = virtualDirectory + "/" + name; 
               node.setAttributeValue("xlink:href", virtualPath); 
            } else { 
               System.out.println("Does not contain a valid data URI"); 
            } 
         } 
      } 
      return true; 
   }; 
 
   RasterCodecs codecs = new RasterCodecs(); 
   // Use 300 DPI when loading document images 
   codecs.getOptions().getRasterizeDocument().getLoad().setResolution(300); 
   // Load the first page as SVG 
   SvgDocument svgDocument = (SvgDocument) codecs.loadSvg(srcFilePath, 1, null); 
 
   if (!svgDocument.isFlat()) 
      svgDocument.flat(null); 
   if (!svgDocument.getBounds().isValid()) 
      svgDocument.calculateBounds(false); 
 
   // Save this SVG to disk, report the size 
   svgDocument.saveToFile(beforeSvgFile, null); 
   System.out.println("Before unembedding the image, size is " + new File(beforeSvgFile).length()); 
 
   // Now enumerate the elements to replace each embedded image with a URL 
   // Since we are going to modify the SVG, call BeginUpdate/EndUpdate to speed up 
   // the process 
   svgDocument.beginUpdate(); 
   SvgEnumerateOptions svgEnumerateOptions = new SvgEnumerateOptions(); 
   svgEnumerateOptions.setEnumerateDirection(SvgEnumerateDirection.TOP_TO_BOTTOM); 
 
   svgDocument.enumerateElements(svgEnumerateOptions, callback, null); 
   svgDocument.endUpdate(); 
 
   // Save this SVG to disk again, report the size, should be alot smaller since 
   // the image are unembedded and stored as external resources 
   svgDocument.saveToFile(afterSvgFile, null); 
 
   System.out.println("After unembedding the image, size is " + new File(afterSvgFile).length()); 
   assertTrue(new File(afterSvgFile).length() != new File(beforeSvgFile).length()); 
}

Requirements

Target Platforms

Reference

SvgDocument Class

SvgDocument Members

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Help Version 23.0.2024.5.23

Leadtools.Svg Assembly

Introduction

Getting Started

Namespaces

Leadtools.Svg Namespace

Assemblies