transformChanged Event

Summary

Occurs when the transformation matrix of the view or any of the items change.

Syntax
TypeScript
JavaScript
Object.defineProperty(ImageViewer.prototype,'transformChanged', 
	get: function(), 
	set: function(value) 
) 
transformChanged: LeadEvent; 
Event Data
ParameterTypeDescription
sendervarThe source of the event.
Remarks

This event is raised when the transformation matrix of the view or any of the items change by either a programmatic modification or end-user interaction through the user interface.

The event is raised by the UpdateTransform method after all the calculations needed is performed. It gives the user a chance to catch all notification when anything in the viewer changes.

For more information, refer to Image Viewer Items, Image Viewer Transformation, Image Viewer Bounds and Transform, and Image Viewer Layouts.

Example

This example will hook to the TransformChanged event of the viewer and track the current, first, and largest (most visible) visible items.

Run the demo, click the button and notice that as you pan and zoom the viewer, the values are displayed in the label.

TransformChanged.ts
ImageViewer.ts
TransformChanged.js
ImageViewer.js
TransformChanged.html
import { ImageViewer_Example } from "../ImageViewer"; 
 
export class ImageViewer_TransformChangedExample { 
   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 
      viewer.viewLayout = new lt.Controls.ImageViewerVerticalViewLayout(); 
      // Add padding and margins 
      viewer.itemSpacing = lt.LeadSizeD.create(10, 10); 
      viewer.itemPadding = lt.Controls.ControlPadding.create(0, 0, 0, 20); 
 
      // Add 4 items to the viewer 
      for (let i = 0; i < 4; i++) { 
         const item: lt.Controls.ImageViewerItem = new lt.Controls.ImageViewerItem(); 
         item.url = "https://demo.leadtools.com/images/jpeg/cannon.jpg"; 
         item.text = "Item " + i; 
         viewer.items.add(item); 
      } 
 
      const output = document.getElementById("output"); 
 
      // Hook to the TransformChanged event for when we pan and zoom 
      viewer.transformChanged.add((sender, e) => { 
         // Get the first and largest visible items 
         const firstVisibleIndex: lt.Controls.ImageViewerItemPart = viewer.getFirstVisibleItemIndex(lt.Controls.ImageViewerItemPart.item); 
         const largestVisibleIndex: number = viewer.getLargestVisibleItemIndex(lt.Controls.ImageViewerItemPart.item); 
 
         let text: string = ""; 
         text += "<p>First Visible (0-Based): " + (firstVisibleIndex !== -1 ? firstVisibleIndex : "[None]") + "</p>"; 
         text += "<p>Most/Largest Visible (0-Based): " + (largestVisibleIndex !== -1 ? largestVisibleIndex : "[None]") + "</p>"; 
         output.innerHTML = text; 
      }); 
   } 
} 
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_TransformChangedExample { 
   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 
      viewer.viewLayout = new lt.Controls.ImageViewerVerticalViewLayout(); 
      // Add padding and margins 
      viewer.itemSpacing = lt.LeadSizeD.create(10, 10); 
      viewer.itemPadding = lt.Controls.ControlPadding.create(0, 0, 0, 20); 
 
      // Add 4 items to the viewer 
      for (let i = 0; i < 4; i++) { 
         const item = new lt.Controls.ImageViewerItem(); 
         item.url = "https://demo.leadtools.com/images/jpeg/cannon.jpg"; 
         item.text = "Item " + i; 
         viewer.items.add(item); 
      } 
 
      const output = document.getElementById("output"); 
 
      // Hook to the TransformChanged event for when we pan and zoom 
      viewer.transformChanged.add((sender, e) => { 
         // Get the first and largest visible items 
         const firstVisibleIndex = viewer.getFirstVisibleItemIndex(lt.Controls.ImageViewerItemPart.item); 
         const largestVisibleIndex = viewer.getLargestVisibleItemIndex(lt.Controls.ImageViewerItemPart.item); 
 
         let text = ""; 
         text += "<p>First Visible (0-Based): " + (firstVisibleIndex !== -1 ? firstVisibleIndex : "[None]") + "</p>"; 
         text += "<p>Most/Largest Visible (0-Based): " + (largestVisibleIndex !== -1 ? largestVisibleIndex : "[None]") + "</p>"; 
         output.innerHTML = text; 
      }); 
   } 
} 
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 | TransformChanged</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.TransformChanged(); 
 
   }; 
</script> 
</html> 
Requirements

Target Platforms

Help Version 22.0.2021.9.24
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Leadtools.Controls Assembly
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© 1991-2022 LEAD Technologies, Inc. All Rights Reserved.