postRender Event

Summary

Occurs after the view is rendered.

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

For more information, refer to Image Viewer Rendering.

Example

This example will show how to customize the view rendering to draw extra shapes with and without transformation.

PostRender.ts
ImageViewer.ts
PostRender.js
ImageViewer.js
PostRender.html
import { ImageViewer_Example } from "../ImageViewer"; 
 
export class ImageViewer_PostRenderExample { 
   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(); 
      // 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: 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); 
      } 
 
      // Render on the view 
      viewer.postRender.add((sender, e) => { 
         // Rendering the whole view 
         const ctx: CanvasRenderingContext2D = 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: lt.LeadMatrix = 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: lt.Controls.ImageViewerItem = e.item; 
         const ctx: CanvasRenderingContext2D = e.context; 
 
         ctx.save(); 
         // Get the bounding rectangle for the image 
         const bounds: lt.LeadRectD = lt.LeadRectD.create(0, 0, item.size.width, item.size.height); 
 
         // Add the image transform to the graphics 
         const t: lt.LeadMatrix = 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 
   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> 
Requirements

Target Platforms

Help Version 22.0.2021.9.24
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© 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.