imageLoading Event

Summary

Occurs just before an image starts loading as the result of a URL update.

Syntax
TypeScript
JavaScript
Object.defineProperty(ImageViewer.prototype,'imageLoading', 
	get: function(), 
	set: function(value) 
) 
imageLoading: LeadEvent; 
Remarks

When ImageUrl, BackImageUrl, Url, or BackImageUrl is set, a new ImageLoader is created to handle the loading process. Just before Run is called, the ImageLoading event is fired to give callbacks a chance to modify properties of the image load through ImageLoader. Properties such as UrlMode can be changed, and if the request uses AJAX (per, for example, AjaxDataUrl), then headers can be added or changed via Headers.

This event will also be fired when AutoRemoveItemElements is true and an image must be reloaded because an ImageViewerItem comes back into view.

Example
ImageLoading.ts
ImageViewer.ts
ImageLoading.js
ImageViewer.js
ImageLoading.html
import { ImageViewer_Example } from "../ImageViewer"; 
 
export class ImageViewer_ImageLoadingExample { 
   private viewerExample; 
   constructor() { 
      this.viewerExample = new ImageViewer_Example(this.run); 
   } 
 
   private run = (viewer: lt.Controls.ImageViewer) => { 
      viewer.items.clear(); 
      viewer.viewLayout = new lt.Controls.ImageViewerVerticalViewLayout(); 
 
      const output = document.getElementById("output"); 
      viewer.imageLoading.add((sender, e) => { 
         // We now have access to imageLoader and item 
         // We can change any settings we want 
         const imageLoader: lt.ImageLoader = e.imageLoader; 
         output.innerHTML = "Image about to load: " + imageLoader.url; 
      }); 
 
      let item: lt.Controls.ImageViewerItem = new lt.Controls.ImageViewerItem(); 
      // Image will not load immediately. Must be added to ImageViewer. 
      item.url = "https://demo.leadtools.com/images/png/pngimage.png"; 
      item.text = "Text"; 
 
      setTimeout(() => { 
         // We set a timeout for 4 seconds, to show that the event 
         // will execute right before image is loaded 
         viewer.items.add(item); 
      }, 1100); 
   } 
} 
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_FloaterExample { 
   viewerExample; 
   constructor() { 
      this.viewerExample = new ImageViewer_Example(this.run); 
   } 
 
   run = (viewer) => { 
      viewer.items.clear(); 
      viewer.viewLayout = new lt.Controls.ImageViewerVerticalViewLayout(); 
 
      const output = document.getElementById("output"); 
      viewer.imageLoading.add((sender, e) => { 
         // We now have access to imageLoader and item 
         // We can change any settings we want 
         const imageLoader = e.imageLoader; 
         output.innerHTML = "Image about to load: " + imageLoader.url; 
      }); 
 
      let item = new lt.Controls.ImageViewerItem(); 
      // Image will not load immediately. Must be added to ImageViewer. 
      item.url = "https://demo.leadtools.com/images/png/pngimage.png"; 
      item.text = "Text"; 
 
      setTimeout(() => { 
         // We set a timeout for 4 seconds, to show that the event 
         // will execute right before image is loaded 
         viewer.items.add(item); 
      }, 1100); 
   } 
} 
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 | ImageLoading</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.ImageLoading(); 
 
   }; 
</script> 
</html> 
Event Data
ParameterTypeDescription
sendervarThe source of the event.
eImageViewerImageLoadingEventArgsThe event data.
Requirements

Target Platforms

Help Version 22.0.2021.9.24
Products | Support | Contact Us | Intellectual Property Notices
© 1991-2021 LEAD Technologies, Inc. All Rights Reserved.

Leadtools.Controls Assembly
Products | Support | Contact Us | Intellectual Property Notices
© 1991-2021 LEAD Technologies, Inc. All Rights Reserved.