loadPicture Event

Summary

Occurs when a picture object has been finished loading its source image.

Syntax
TypeScript
JavaScript
Object.defineProperty(AnnRenderingEngine.prototype,'loadPicture', 
	get: function(), 
	set: function(value) 
) 
loadPicture: LeadEvent; 

Remarks

AnnLoadPictureEventArgs

In the LEADTOOLS Annotation framework, the source image in picture objects is not loaded till render time. For example, when you first render an annotation object that contains a picture, such as the AnnHotspotObject or AnnPointObject, the framework will load the image in AnnPicture.Source in the background. While the image is loading, the framework will use a placeholder rectangle to render the object position and size. When the image is fully loaded, the framework will fire the LoadPicture event and renders the new image instead of the placeholder.

LoadingPictureStroke and LoadingPictureFill are the objects to use for stroking and filling the placeholder rectangle. Default values are a white stroke on a black background.

The LoadPicture event contains data about the picture that finished loading such as the Picture object itself and the owner AnnObject. Also, the event data contains the Error property that will be populated if an error occurred.

Loading an image in the background is an efficient and easy way to start drawing an annotation object without waiting for all the resources to be available in the browser. This is especially true if the object contains a picture with a source URL on a server machine and takes a few seconds to download.

Example

This example will create a picture from a resource in a remote server and use it with a hotspot annotation object. It will then uses automation to start drawing the object as the image is being loaded.

LoadPicture.ts
EngineHelper.ts
LoadPicture.js
EngineHelper.js
LoadPicture.html
import { EngineHelper } from "../utilities/EngineHelper"; 
 
export class AnnRenderingEngine_LoadPicture { 
   constructor() { 
      const helper = new EngineHelper(); 
      helper.run(this.loadPicture); 
   } 
 
   loadPicture = (automation: lt.Annotations.Automation.AnnAutomation) => { 
      // get the current rendering engine 
      let renderingEngine: lt.Annotations.Engine.AnnRenderingEngine = automation.automationControl.renderingEngine; 
 
      // Change the default loading object placeholder to be a green border with semi-transparent background 
      const stroke: lt.Annotations.Engine.AnnStroke = lt.Annotations.Engine.AnnStroke.create( 
         lt.Annotations.Engine.AnnSolidColorBrush.create("green"), 
         lt.LeadLengthD.create(1)); 
      const fill: lt.Annotations.Engine.AnnBrush = lt.Annotations.Engine.AnnSolidColorBrush.create("rgba(0, 0, 0, 0.5)"); 
 
      renderingEngine.loadingPictureStroke = stroke; 
      renderingEngine.loadingPictureFill = fill; 
 
      // Hook to the LoadPicture event 
      renderingEngine.add_loadPicture((sender, e) => { 
         // e is AnnLoadPictureEventArgs 
         // Check if an error occurred 
         if (e.error != null) { 
            // Show info about the error 
            let str = e.error.message; 
            str += "\nSource: " + e.picture.source; 
            str += "\nOwner object: " + e.annObject.friendlyName; 
            alert(str); 
         } 
 
         // Re-render the container after picture get loaded 
         automation.invalidate(lt.LeadRectD.empty); 
      }); 
 
      // Create a new AnnHotspotObject with a picture from a remote server 
      const inch: number = 720; 
      const hotspot: lt.Annotations.Engine.AnnHotspotObject = new lt.Annotations.Engine.AnnHotspotObject(); 
      // Add the object at location 1,1 inch with size 4,2 inches 
      hotspot.rect = lt.LeadRectD.create(1 * inch, 1 * inch, 4 * inch, 2 * inch); 
      // Set its picture 
      const picture: lt.Annotations.Engine.AnnPicture = new lt.Annotations.Engine.AnnPicture(""); 
      picture.source = "https://www.leadtools.com/images/page_graphics/leadlogo.png"; 
 
      //NOTE: CORS can cause toDataUrl to fail 
      //      Alternatively, use a local resource 
      //picture.source = "Resources/leadlogo.png"; 
 
      hotspot.picture = picture; 
 
      // Add it to the container 
      const container: lt.Annotations.Engine.AnnContainer = automation.container; 
      container.children.add(hotspot); 
 
      // Render the container 
      automation.invalidate(lt.LeadRectD.empty); 
   } 
} 
export class EngineHelper { 
   // Automation object 
   protected _automation: lt.Annotations.Automation.AnnAutomation = null; 
   // Image viewer 
   protected _viewer: lt.Controls.ImageViewer = null; 
 
   constructor() { 
      // Set the LEADTOOLS license. Replace this with your actual license file 
      lt.RasterSupport.setLicenseUri("https://demo.leadtools.com/licenses/v200/LEADTOOLSEVAL.txt", "EVAL", null); 
   } 
 
   public run(callback?: (automation: lt.Annotations.Automation.AnnAutomation, viewer: lt.Controls.ImageViewer) => void): void { 
      // Create the viewer 
      const imageViewerDiv = document.getElementById("imageViewerDiv"); 
      const createOptions: lt.Controls.ImageViewerCreateOptions = new lt.Controls.ImageViewerCreateOptions(imageViewerDiv); 
      const viewer: lt.Controls.ImageViewer = new lt.Controls.ImageViewer(createOptions); 
      viewer.autoCreateCanvas = true; 
      this._viewer = viewer; 
 
      // PanZoom interactive mode 
      const panZoom: lt.Controls.ImageViewerPanZoomInteractiveMode = new lt.Controls.ImageViewerPanZoomInteractiveMode(); 
 
      // Create an instance of the Automation control object that works with LEADTOOLS ImageViewer 
      const imageViewerAutomationControl: lt.Demos.Annotations.ImageViewerAutomationControl = new lt.Demos.Annotations.ImageViewerAutomationControl(); 
      // Attach our image viewer 
      imageViewerAutomationControl.imageViewer = viewer; 
 
      // Set the image viewer interactive mode 
      const automationInteractiveMode: lt.Demos.Annotations.AutomationInteractiveMode = new lt.Demos.Annotations.AutomationInteractiveMode(); 
      automationInteractiveMode.automationControl = imageViewerAutomationControl; 
 
      // Set the image URL 
      viewer.imageUrl = "http://demo.leadtools.com/images/png/pngimage.png"; 
 
      // Create and set up the automation manager using the HTML5 rendering engine 
      const renderingEngine: lt.Annotations.Rendering.AnnHtml5RenderingEngine = new lt.Annotations.Rendering.AnnHtml5RenderingEngine(); 
      const manager: lt.Annotations.Automation.AnnAutomationManager = lt.Annotations.Automation.AnnAutomationManager.create(renderingEngine); 
 
      // Create default automation objects 
      manager.createDefaultObjects(); 
 
      // Add the objects to the objects select element 
      const currentObjectIdSelect = document.getElementById("currentObjectIdSelect") as HTMLSelectElement; 
      // Add the PanZoom option 
      currentObjectIdSelect.options[currentObjectIdSelect.options.length] = new Option("Pan/Zoom", lt.Annotations.Engine.AnnObject.none.toString()); 
 
      const automationObjCount: number = manager.objects.count; 
      for (let i = 0; i < automationObjCount; i++) { 
         // Get the object 
         const automationObj: lt.Annotations.Automation.AnnAutomationObject = manager.objects.item(i); 
 
         // Add its name to the select element 
         const name: string = automationObj.name; 
         const id: string = automationObj.id.toString(); 
         currentObjectIdSelect.options[currentObjectIdSelect.options.length] = new Option(name, id); 
      } 
 
      // Hook to its change event 
      currentObjectIdSelect.addEventListener("change", () => { 
         // Get the object ID 
         const id: number = parseInt(currentObjectIdSelect.options[currentObjectIdSelect.selectedIndex].value); 
 
         // Set it as the current object in the manager 
         manager.currentObjectId = id; 
 
         // If this is the "Pan/Zoom" option, then back to pan zoom, otherwise, set our automation control 
         if (id == lt.Annotations.Engine.AnnObject.none) { 
            viewer.defaultInteractiveMode = panZoom; 
         } 
         else { 
            viewer.defaultInteractiveMode = automationInteractiveMode; 
         } 
      }); 
 
      // When the current object ID changes, we need to update our select 
      manager.add_currentObjectIdChanged((sender, e) => { 
         const currentObjectId: number = manager.currentObjectId; 
         for (let i = 0; i < currentObjectIdSelect.options.length; i++) { 
            const id: number = parseInt(currentObjectIdSelect.options[i].value); 
            if (id === currentObjectId) { 
               currentObjectIdSelect.selectedIndex = i; 
               break; 
            } 
         } 
      }); 
 
      // Pan zoom by default 
      viewer.defaultInteractiveMode = panZoom; 
 
      // set up the automation (will create the container as well) 
      const automation: lt.Annotations.Automation.AnnAutomation = new lt.Annotations.Automation.AnnAutomation(manager, imageViewerAutomationControl); 
      this._automation = automation; 
 
      // Add handler to update the container size when the image size changes 
      viewer.itemChanged.add((sender, e) => { 
         const container: lt.Annotations.Engine.AnnContainer = automation.container; 
         container.size = container.mapper.sizeToContainerCoordinates(viewer.imageSize); 
 
         //Create new canvas data provider for the new image 
         const canvasDataProvider: lt.Demos.Annotations.CanvasDataProvider = new lt.Demos.Annotations.CanvasDataProvider(viewer.activeItem.canvas); 
         imageViewerAutomationControl.automationDataProvider = canvasDataProvider; 
 
      }); 
 
      // set up this automation as the active one 
      this._automation.active = true; 
 
      const exampleButton = document.getElementById("exampleButton"); 
      exampleButton.onclick = () => { 
         if(callback) 
            callback(this._automation, this._viewer); 
      } 
   } 
} 
import { EngineHelper } from "../utilities/EngineHelper"; 
 
export class AnnRenderingEngine_LoadPicture { 
   constructor() { 
      const helper = new EngineHelper(); 
      helper.run(this.loadPicture); 
   } 
 
   loadPicture = (automation) => { 
      // get the current rendering engine 
      let renderingEngine = automation.automationControl.renderingEngine; 
 
      // Change the default loading object placeholder to be a green border with semi-transparent background 
      const stroke = lt.Annotations.Engine.AnnStroke.create( 
         lt.Annotations.Engine.AnnSolidColorBrush.create("green"), 
         lt.LeadLengthD.create(1)); 
      const fill = lt.Annotations.Engine.AnnSolidColorBrush.create("rgba(0, 0, 0, 0.5)"); 
 
      renderingEngine.loadingPictureStroke = stroke; 
      renderingEngine.loadingPictureFill = fill; 
 
      // Hook to the LoadPicture event 
      renderingEngine.add_loadPicture((sender, e) => { 
         // e is AnnLoadPictureEventArgs 
         // Check if an error occurred 
         if (e.error != null) { 
            // Show info about the error 
            let str = e.error.message; 
            str += "\nSource: " + e.picture.source; 
            str += "\nOwner object: " + e.annObject.friendlyName; 
            alert(str); 
         } 
 
         // Re-render the container after picture get loaded 
         automation.invalidate(lt.LeadRectD.empty); 
      }); 
 
      // Create a new AnnHotspotObject with a picture from a remote server 
      const inch = 720; 
      const hotspot = new lt.Annotations.Engine.AnnHotspotObject(); 
      // Add the object at location 1,1 inch with size 4,2 inches 
      hotspot.rect = lt.LeadRectD.create(1 * inch, 1 * inch, 4 * inch, 2 * inch); 
      // Set its picture 
      const picture = new lt.Annotations.Engine.AnnPicture(""); 
      picture.source = "https://www.leadtools.com/images/page_graphics/leadlogo.png"; 
 
      //NOTE: CORS can cause toDataUrl to fail 
      //      Alternatively, use a local resource 
      //picture.source = "Resources/leadlogo.png"; 
 
      hotspot.picture = picture; 
 
      // Add it to the container 
      const container = automation.container; 
      container.children.add(hotspot); 
 
      // Render the container 
      automation.invalidate(lt.LeadRectD.empty); 
   } 
} 
export class EngineHelper { 
   // Automation object 
   _automation = null; 
   // Image viewer 
   _viewer = null; 
 
   constructor() { 
      // Set the LEADTOOLS license. Replace this with your actual license file 
      lt.RasterSupport.setLicenseUri("https://demo.leadtools.com/licenses/v200/LEADTOOLSEVAL.txt", "EVAL", null); 
   } 
 
   run(callback) { 
      // Create the viewer 
      const imageViewerDiv = document.getElementById("imageViewerDiv"); 
      const createOptions = new lt.Controls.ImageViewerCreateOptions(imageViewerDiv); 
      const viewer = new lt.Controls.ImageViewer(createOptions); 
      viewer.autoCreateCanvas = true; 
      this._viewer = viewer; 
 
      // PanZoom interactive mode 
      const panZoom = new lt.Controls.ImageViewerPanZoomInteractiveMode(); 
 
      // Create an instance of the Automation control object that works with LEADTOOLS ImageViewer 
      const imageViewerAutomationControl = new lt.Demos.Annotations.ImageViewerAutomationControl(); 
      // Attach our image viewer 
      imageViewerAutomationControl.imageViewer = viewer; 
 
      // Set the image viewer interactive mode 
      const automationInteractiveMode = new lt.Demos.Annotations.AutomationInteractiveMode(); 
      automationInteractiveMode.automationControl = imageViewerAutomationControl; 
 
      // Set the image URL 
      viewer.imageUrl = "http://demo.leadtools.com/images/png/pngimage.png"; 
 
      // Create and set up the automation manager using the HTML5 rendering engine 
      const renderingEngine = new lt.Annotations.Rendering.AnnHtml5RenderingEngine(); 
      const manager = lt.Annotations.Automation.AnnAutomationManager.create(renderingEngine); 
 
      // Create default automation objects 
      manager.createDefaultObjects(); 
 
      // Add the objects to the objects select element 
      const currentObjectIdSelect = document.getElementById("currentObjectIdSelect"); 
      // Add the PanZoom option 
      currentObjectIdSelect.options[currentObjectIdSelect.options.length] = new Option("Pan/Zoom", lt.Annotations.Engine.AnnObject.none.toString()); 
 
      const automationObjCount = manager.objects.count; 
      for (let i = 0; i < automationObjCount; i++) { 
         // Get the object 
         const automationObj = manager.objects.item(i); 
 
         // Add its name to the select element 
         const name = automationObj.name; 
         const id = automationObj.id.toString(); 
         currentObjectIdSelect.options[currentObjectIdSelect.options.length] = new Option(name, id); 
      } 
 
      // Hook to its change event 
      currentObjectIdSelect.addEventListener("change", () => { 
         // Get the object ID 
         const id = parseInt(currentObjectIdSelect.options[currentObjectIdSelect.selectedIndex].value); 
 
         // Set it as the current object in the manager 
         manager.currentObjectId = id; 
 
         // If this is the "Pan/Zoom" option, then back to pan zoom, otherwise, set our automation control 
         if (id == lt.Annotations.Engine.AnnObject.none) { 
            viewer.defaultInteractiveMode = panZoom; 
         } 
         else { 
            viewer.defaultInteractiveMode = automationInteractiveMode; 
         } 
      }); 
 
      // When the current object ID changes, we need to update our select 
      manager.add_currentObjectIdChanged((sender, e) => { 
         const currentObjectId = manager.currentObjectId; 
         for (let i = 0; i < currentObjectIdSelect.options.length; i++) { 
            const id = parseInt(currentObjectIdSelect.options[i].value); 
            if (id === currentObjectId) { 
               currentObjectIdSelect.selectedIndex = i; 
               break; 
            } 
         } 
      }); 
 
      // Pan zoom by default 
      viewer.defaultInteractiveMode = panZoom; 
 
      // set up the automation (will create the container as well) 
      const automation = new lt.Annotations.Automation.AnnAutomation(manager, imageViewerAutomationControl); 
      this._automation = automation; 
 
      // Add handler to update the container size when the image size changes 
      viewer.itemChanged.add((sender, e) => { 
         const container = automation.container; 
         container.size = container.mapper.sizeToContainerCoordinates(viewer.imageSize); 
 
         //Create new canvas data provider for the new image 
         const canvasDataProvider = new lt.Demos.Annotations.CanvasDataProvider(viewer.activeItem.canvas); 
         imageViewerAutomationControl.automationDataProvider = canvasDataProvider; 
 
      }); 
 
      // set up this automation as the active one 
      this._automation.active = true; 
 
      const exampleButton = document.getElementById("exampleButton"); 
      exampleButton.onclick = () => { 
         if(callback) 
            callback(this._automation, this._viewer); 
      } 
   } 
} 
<!doctype html> 
<html lang="en"> 
<title>AnnRenderingEngine Example | LoadPicture</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.Annotations.BatesStamp.js"></script> 
   <script src="../LT/Leadtools.Demos.js"></script> 
   <script src="../LT/Leadtools.Demos.Annotations.js"></script> 
   <style> 
      #imageViewerDiv { 
         border: 1px solid #000000; 
         width: 800px; 
         height: 800px; 
         background-color: #7F7F7F; 
      } 
   </style> 
   <!-- All demo files are bundled and appended to the window --> 
   <script src="../../bundle.js" type="text/javascript"></script> 
</head> 
 
<body> 
   <p>Either Pan/Zoom or Annotations mode. In annotations mode, draw new objects or edit them.</p> 
   <div> 
      <select id="currentObjectIdSelect"></select> 
   </div> 
   <div> 
      <input type="button" id="exampleButton" value="Example" /> 
      <label id="exampleLabel" /> 
   </div> 
   <div id="imageViewerDiv" /> 
</body> 
 
<script> 
   window.onload = () => new window.examples.AnnRenderingEngine.LoadPicture(); 
</script> 
</html> 

Event Data
ParameterTypeDescription
sendervarThe source of the event.
eAnnLoadPictureEventArgsThe event data.

Requirements

Target Platforms

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Leadtools.Annotations.Engine Assembly