preRenderItem Event

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_PostRenderExample { 
   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(); 
      // Make sure the item size is larger than the image size (thumbnails mode) 
      viewer.itemPadding = lt.Controls.ControlPadding.create(8, 8, 8, 20); 
      viewer.itemBorderThickness = 3; 
      viewer.itemMargin = lt.Controls.ControlPadding.createAll(10); 
 
      // 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); 
      } 
 
      // Render on the view 
      viewer.postRender.add((sender, e) => { 
         // Rendering the whole view 
         const ctx = e.context; 
 
         // Blue ellipse at fixed position. This will stay the same and will not scroll or zoom 
         ctx.beginPath(); 
         ctx.arc(50, 50, 30, 0, Math.PI * 2); 
         ctx.closePath(); 
         ctx.fillStyle = "rgba(0, 0, 255, .5)"; 
         ctx.fill(); 
 
         // Red ellipse at relative position, this will scroll and zoom with the view 
         ctx.save(); 
 
         const t = viewer.viewTransform; 
         ctx.transform(t.m11, t.m12, t.m21, t.m22, t.offsetX, t.offsetY); 
 
         ctx.beginPath(); 
         ctx.arc(50, 50, 30, 0, Math.PI * 2); 
         ctx.closePath(); 
         ctx.fillStyle = "rgba(255, 0, 0, .5)"; 
         ctx.fill(); 
 
         ctx.restore(); 
      }); 
 
      // Render on each item 
      viewer.postRenderItem.add((sender, e) => { 
         const item = e.item; 
         const ctx = e.context; 
 
         ctx.save(); 
         // Get the bounding rectangle for the image 
         const bounds = lt.LeadRectD.create(0, 0, item.size.width, item.size.height); 
 
         // Add the image transform to the graphics 
         const t = viewer.getItemImageTransform(item); 
         ctx.transform(t.m11, t.m12, t.m21, t.m22, t.offsetX, t.offsetY); 
 
         // Red hilight on right half of each item image 
         ctx.fillStyle = "rgba(255, 0, 0, .5)"; 
         ctx.fillRect(bounds.x + (bounds.width / 2), bounds.y, bounds.width / 2, bounds.height); 
         ctx.restore(); 
      }); 
   } 
} 

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 | PostRender</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.PostRender(); 
 
   }; 
</script> 
</html>