beginUpdate Method

Summary

Stops the viewer from updating the transformations matrices, view layout and rendering the content if any change is applied. This is useful to increase the control's speed efficiency.

Syntax
TypeScript
JavaScript
ImageViewer.prototype.beginUpdate = function() 
beginUpdate(): void; 
Remarks

The BeginUpdate method will cause the control to not update the image viewing transformation or invalidate the display when any changes to the control's properties or the image is applied. When the user calls the EndUpdate method, the viewer will then update the transformation and invalidate the display to show all the changes that have been made.

For better visual results and for speed efficiency, it is recommended you surround multiple calls that will cause a render or transformation change between BeginUpdate and EndUpdate.

Calls to BeginUpdate and EndUpdate are accumulative. Each call to BeginUpdate must be matched with a corresponding call to EndUpdate or else updates to the transform won't be applied.

When the final EndUpdate is called and updating is resumed, the viewer will call UpdateTransform and Invalidate to re-calculate the transformations matrices and layout and render the new content.

BeginUpdate will call BeginRender and BeginTransform while EndUpdate will call EndRender and EndTransform. The most common usage of stopping the viewer from updating will usually involve disabling both transformations update and rendering. If only rendering or only transformation is to be disabled for a specific need, then use BeginRender and BeginTransform individually.

For more information, refer to Image Viewer Rendering.

Example
Items.ts
ImageViewer.ts
Items.js
ImageViewer.js
Items.html
import { ImageViewer_Example } from "../ImageViewer"; 
 
export class ImageViewer_ItemsExample { 
   private viewerExample; 
   constructor() { 
      this.viewerExample = new ImageViewer_Example(this.run); 
   } 
 
   private run = (viewer: lt.Controls.ImageViewer) => { 
      // Clear all the images already the viewer 
      viewer.items.clear(); 
 
      // Use vertical view layout to show multiple items 
      viewer.viewLayout = new lt.Controls.ImageViewerVerticalViewLayout(); 
      viewer.imageBorderThickness = 1; 
 
      // Add 4 items to the viewer 
      for (let page = 1; page <= 4; page++) { 
         const item: lt.Controls.ImageViewerItem = new lt.Controls.ImageViewerItem(); 
         const imageUrl: string = "https://demo.leadtools.com/images/png/ocr" + page.toString() + ".png"; 
         item.text = "Page " + page; 
         item.url = imageUrl; 
         viewer.items.add(item); 
      } 
 
      let panZoom: lt.Controls.ImageViewerPanZoomInteractiveMode = viewer.interactiveModes.findById(lt.Controls.ImageViewerInteractiveMode.panZoomModeId) as lt.Controls.ImageViewerPanZoomInteractiveMode; 
      panZoom.minimumScaleFactor = 0.01; 
      viewer.zoom(lt.Controls.ControlSizeMode.fitHeight, .25, viewer.defaultZoomOrigin); 
 
      // Show the count 
      alert("The count should be 4: " + viewer.items.count); 
 
      // Not required, just used for the example 
      setTimeout(() => { 
 
         // Remove the item at index 1 (page 2) 
         viewer.items.removeAt(1); 
         alert("After removing an item, the count should be 3: " + viewer.items.count); 
 
         // Not required, just used for the example 
         setTimeout(() => { 
 
            // Loop through each item and show the text. Since we removed page 2, it must say 1, 3, 4 
            let lines: string[] = []; 
            for (let i = 0; i < viewer.items.count; i++) { 
               const item: lt.Controls.ImageViewerItem = viewer.items.item(i); 
               lines.push("Item " + i + " has text '" + item.text + "'"); 
            } 
            alert(lines.join("\r\n")); 
 
         }, 1000); 
      }, 1000); 
   } 
} 
export class ImageViewer_Example { 
   // LEADTOOLS ImageViewer to be used with this example 
   protected imageViewer: lt.Controls.ImageViewer = null; 
   // Generic state value used by the examples 
   public timesClicked: number = 0; 
 
   constructor(callback?: (viewer: lt.Controls.ImageViewer) => void) { 
      // Set the LEADTOOLS license. Replace this with your actual license file 
      lt.RasterSupport.setLicenseUri("https://demo.leadtools.com/licenses/js/LEADTOOLSEVAL.txt", "EVAL", null); 
 
      // Create an image viewer inside the imageViewerDiv element 
      const imageViewerDiv = document.getElementById("imageViewerDiv"); 
      const createOptions: lt.Controls.ImageViewerCreateOptions = new lt.Controls.ImageViewerCreateOptions(imageViewerDiv); 
      this.imageViewer = new lt.Controls.ImageViewer(createOptions); 
      this.imageViewer.viewVerticalAlignment = lt.Controls.ControlAlignment.center; 
      this.imageViewer.viewHorizontalAlignment = lt.Controls.ControlAlignment.center; 
      this.imageViewer.autoCreateCanvas = true; 
 
      // Add Pan/Zoom interactive mode 
      // Click and drag to pan, CTRL-Click and drag to zoom in and out 
      this.imageViewer.interactiveModes.add(new lt.Controls.ImageViewerPanZoomInteractiveMode()); 
 
      // Load an image 
      this.imageViewer.imageUrl = "https://demo.leadtools.com/images/jpeg/cannon.jpg"; 
 
      this.imageViewer.zoom(lt.Controls.ControlSizeMode.fit, .9, this.imageViewer.defaultZoomOrigin); 
 
      const exampleButton = document.getElementById("exampleButton"); 
      exampleButton.addEventListener("click", () => { 
         this.timesClicked++; 
         // Run the example 
         if (callback) 
            callback(this.imageViewer); 
      }); 
   } 
} 
import { ImageViewer_Example } from "../ImageViewer"; 
 
export class ImageViewer_ItemsExample { 
   viewerExample; 
   constructor() { 
      this.viewerExample = new ImageViewer_Example(this.run); 
   } 
 
   run = (viewer) => { 
      // Clear all the images already the viewer 
      viewer.items.clear(); 
 
      // Use vertical view layout to show multiple items 
      viewer.viewLayout = new lt.Controls.ImageViewerVerticalViewLayout(); 
      viewer.imageBorderThickness = 1; 
 
      // Add 4 items to the viewer 
      for (let page = 1; page <= 4; page++) { 
         const item = new lt.Controls.ImageViewerItem(); 
         const imageUrl = "https://demo.leadtools.com/images/png/ocr" + page.toString() + ".png"; 
         item.text = "Page " + page; 
         item.url = imageUrl; 
         viewer.items.add(item); 
      } 
 
      let panZoom = viewer.interactiveModes.findById(lt.Controls.ImageViewerInteractiveMode.panZoomModeId); 
      panZoom.minimumScaleFactor = 0.01; 
      viewer.zoom(lt.Controls.ControlSizeMode.fitHeight, .25, viewer.defaultZoomOrigin); 
 
      // Show the count 
      alert("The count should be 4: " + viewer.items.count); 
 
      // Not required, just used for the example 
      setTimeout(() => { 
 
         // Remove the item at index 1 (page 2) 
         viewer.items.removeAt(1); 
         alert("After removing an item, the count should be 3: " + viewer.items.count); 
 
         // Not required, just used for the example 
         setTimeout(() => { 
 
            // Loop through each item and show the text. Since we removed page 2, it must say 1, 3, 4 
            let lines = []; 
            for (let i = 0; i < viewer.items.count; i++) { 
               const item = viewer.items.item(i); 
               lines.push("Item " + i + " has text '" + item.text + "'"); 
            } 
            alert(lines.join("\r\n")); 
 
         }, 1000); 
      }, 1000); 
   } 
} 
export class ImageViewer_Example { 
   // LEADTOOLS ImageViewer to be used with this example 
   imageViewer = null; 
   // Generic state value used by the examples 
   timesClicked = 0; 
 
   constructor(callback) { 
      // Set the LEADTOOLS license. Replace this with your actual license file 
      lt.RasterSupport.setLicenseUri("https://demo.leadtools.com/licenses/js/LEADTOOLSEVAL.txt", "EVAL", null); 
 
      // Create an image viewer inside the imageViewerDiv element 
      const imageViewerDiv = document.getElementById("imageViewerDiv"); 
      const createOptions = new lt.Controls.ImageViewerCreateOptions(imageViewerDiv); 
      this.imageViewer = new lt.Controls.ImageViewer(createOptions); 
      this.imageViewer.viewVerticalAlignment = lt.Controls.ControlAlignment.center; 
      this.imageViewer.viewHorizontalAlignment = lt.Controls.ControlAlignment.center; 
      this.imageViewer.autoCreateCanvas = true; 
 
      // Add Pan/Zoom interactive mode 
      // Click and drag to pan, CTRL-Click and drag to zoom in and out 
      this.imageViewer.interactiveModes.add(new lt.Controls.ImageViewerPanZoomInteractiveMode()); 
 
      // Load an image 
      this.imageViewer.imageUrl = "https://demo.leadtools.com/images/jpeg/cannon.jpg"; 
 
      this.imageViewer.zoom(lt.Controls.ControlSizeMode.fit, .9, this.imageViewer.defaultZoomOrigin); 
 
      const exampleButton = document.getElementById("exampleButton"); 
      exampleButton.addEventListener("click", () => { 
         this.timesClicked++; 
         // Run the example 
         if (callback) 
            callback(this.imageViewer); 
      }); 
   } 
} 
<!doctype html> 
<html lang="en"> 
<title>Controls Example | Items</title> 
 
<head> 
   <script src="https://code.jquery.com/jquery-2.2.4.min.js" 
      integrity="sha256-BbhdlvQf/xTY9gja0Dq3HiwQF8LaCRTXxZKRutelT44=" crossorigin="anonymous"></script> 
 
   <script src="../../LT/Leadtools.js"></script> 
   <script src="../../LT/Leadtools.Controls.js"></script> 
   <script src="../../LT/Leadtools.Annotations.Engine.js"></script> 
   <script src="../../LT/Leadtools.Annotations.Designers.js"></script> 
   <script src="../../LT/Leadtools.Annotations.Rendering.Javascript.js"></script> 
   <script src="../../LT/Leadtools.Annotations.Automation.js"></script> 
   <script src="../../LT/Leadtools.ImageProcessing.Main.js"></script> 
   <script src="../../LT/Leadtools.ImageProcessing.Color.js"></script> 
   <script src="../../LT/Leadtools.ImageProcessing.Core.js"></script> 
   <script src="../../LT/Leadtools.ImageProcessing.Effects.js"></script> 
   <script src="../../LT/Leadtools.Document.js"></script> 
   <script src="../../LT/Leadtools.Document.Viewer.js"></script> 
   <style> 
      body { 
         font-family: 'Segoe UI', sans-serif; 
      } 
 
      #imageViewerDiv { 
         border: 1px solid #888; 
         width: 500px; 
         height: 500px; 
         background-color: #eee; 
      } 
   </style> 
 
   <!-- All demo files are bundled and appended to the window --> 
   <script src="../../bundle.js" type="text/javascript"></script> 
</head> 
 
<body> 
   <p>Press and drag on the image to pan.</p> 
   <p>Hold down the control key and press and drag on the image or pinch with two fingers to zoom in and out.</p> 
   <div> 
      <button type="button" id="exampleButton">Run Example</button> 
   </div> 
   <div id="imageViewerDiv"></div> 
   <div id="output"></div> 
</body> 
 
<script> 
   window.onload = () => { 
      const example = new window.examples.ImageViewer.Items(); 
 
   }; 
</script> 
</html> 
Requirements

Target Platforms

Help Version 23.0.2024.2.29
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© 1991-2024 LEAD Technologies, Inc. All Rights Reserved.

Leadtools.Controls Assembly
Products | Support | Contact Us | Intellectual Property Notices
© 1991-2023 LEAD Technologies, Inc. All Rights Reserved.