Renders the content of the viewer to an external context.
ImageViewer.prototype.renderRedirect = function(
context,
options,
clipRectangle
)
renderRedirect(
context: CanvasRenderingContext2D,
options: ImageViewerRenderRedirectOptions,
clipRectangle: LeadRectD
): void;
context
Target HTML5 Canvas Element context to render the content of the viewer to.
options
Rendering options
clipRectangle
Clipping rectangle to use.
This method can be used to render the content of the viewer to an external context. ImageViewerPanControl uses this method to show a smaller version of the viewer in a separate external control.
To take a "snapshot" of the viewer surface to perform such operations as screen capture or printing, use RenderRedirect passing it the target context (of the printer or a bitmap).
To perform live updates for operations such as pan window, subscribe to the RedirectRender event to get notified whenever the viewer content is changed. Then call RenderRedirect to render the content of the viewer into the target device.
During the render cycle, the value of IsRenderRedirected will be set to true if this particular rendering operation is targeting an external device other than the viewer itself. If you are performing custom rendering, you can check the value of this property to apply any modification needed.
This example will mirror the content of the viewer into an external canvas
with live updates whenever the viewer content changes.
import { ImageViewer_Example } from "../ImageViewer";
export class ImageViewer_RenderRedirectExample {
private viewerExample;
constructor() {
this.viewerExample = new ImageViewer_Example(this.run);
}
private run = (viewer: lt.Controls.ImageViewer) => {
viewer.itemBorderThickness = 5;
// Create the canvas we will render to
const redirectCanvas = document.createElement("canvas");
redirectCanvas.style.border = "2px solid black";
const redirectWidth: number = 300;
const redirectHeight: number = 300;
redirectCanvas.width = redirectWidth;
redirectCanvas.height = redirectHeight;
// Add it to the page
const output = document.getElementById("output");
output.appendChild(redirectCanvas);
// Add a 20px margin around the redirect render area
const delta: number = 20;
const destRect: lt.LeadRectD = lt.LeadRectD.create(0, 0, redirectWidth, redirectHeight);
destRect.inflate(-delta, -delta);
const options: lt.Controls.ImageViewerRenderRedirectOptions = new lt.Controls.ImageViewerRenderRedirectOptions();
viewer.rotateAngle = 35;
// Use "null" to draw the whole imageViewer
//let item = null;
const item: lt.Controls.ImageViewerItem = viewer.activeItem;
if (item) {
// Don't worry about rendering the below
options.renderBackgrounds = false;
options.renderBorders = false;
options.renderItemStates = false;
options.renderShadows = false;
options.renderText = false;
}
// On imageViewer render...
viewer.redirectRender.add(() => {
let sourceRect: lt.LeadRectD;
let sourceRectClipped: lt.LeadRectD;
if (!item) {
// Draw the whole imageViewer
sourceRect = viewer.getViewBounds(true, false);
sourceRectClipped = viewer.getViewBounds(true, true);
}
else {
// Only draw the rect for the active item
sourceRect = viewer.getItemViewBounds(item, lt.Controls.ImageViewerItemPart.image, false);
sourceRectClipped = viewer.getItemViewBounds(item, lt.Controls.ImageViewerItemPart.image, true);
}
const ctx: CanvasRenderingContext2D = redirectCanvas.getContext("2d");
ctx.clearRect(0, 0, redirectWidth, redirectHeight);
// Draw a rect around the maximum render area
ctx.strokeStyle = "green";
ctx.strokeRect(destRect.x, destRect.y, destRect.width, destRect.height);
// Create the transformation for this rect
options.createTransform(viewer, destRect, sourceRect, lt.Controls.ControlSizeMode.fit, lt.Controls.ControlAlignment.center, lt.Controls.ControlAlignment.center);
// Draw a rect around the actual render area
const clipRect: lt.LeadRectD = options.transform.transformRect(sourceRect);
ctx.strokeStyle = "orange";
ctx.strokeRect(clipRect.x, clipRect.y, clipRect.width, clipRect.height);
// Do the redirect render
viewer.renderRedirect(ctx, options, lt.LeadRectD.empty);
// Show how to draw the item's border
const manuallyComputeRedirectedBorder = () => {
const points: lt.LeadPointD[] = [lt.LeadPointD.create(sourceRectClipped.left, sourceRectClipped.top), lt.LeadPointD.create(sourceRectClipped.right, sourceRectClipped.bottom)];
options.transform.transformPoints(points);
let xmin = points[0].x;
let ymin = points[0].y;
let xmax = xmin;
let ymax = ymin;
for (let i = 1; i < points.length; i++) {
if (points[i].x < xmin) xmin = points[i].x;
if (points[i].x > xmax) xmax = points[i].x;
if (points[i].y < ymin) ymin = points[i].y;
if (points[i].y > ymax) ymax = points[i].y;
}
const bounds: lt.LeadRectD = lt.LeadRectD.fromLTRB(xmin, ymin, xmax, ymax);
ctx.strokeStyle = "blue";
ctx.strokeRect(bounds.x, bounds.y, bounds.width, bounds.height);
};
manuallyComputeRedirectedBorder();
});
viewer.invalidate(lt.LeadRectD.empty);
}
}
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_RenderRedirectExample {
viewerExample;
constructor() {
this.viewerExample = new ImageViewer_Example(this.run);
}
run = (viewer) => {
viewer.itemBorderThickness = 5;
// Create the canvas we will render to
const redirectCanvas = document.createElement("canvas");
redirectCanvas.style.border = "2px solid black";
const redirectWidth = 300;
const redirectHeight = 300;
redirectCanvas.width = redirectWidth;
redirectCanvas.height = redirectHeight;
// Add it to the page
const output = document.getElementById("output");
output.appendChild(redirectCanvas);
// Add a 20px margin around the redirect render area
const delta = 20;
const destRect = lt.LeadRectD.create(0, 0, redirectWidth, redirectHeight);
destRect.inflate(-delta, -delta);
const options = new lt.Controls.ImageViewerRenderRedirectOptions();
viewer.rotateAngle = 35;
// Use "null" to draw the whole imageViewer
//let item = null;
const item = viewer.activeItem;
if (item) {
// Don't worry about rendering the below
options.renderBackgrounds = false;
options.renderBorders = false;
options.renderItemStates = false;
options.renderShadows = false;
options.renderText = false;
}
// On imageViewer render...
viewer.redirectRender.add(() => {
let sourceRect;
let sourceRectClipped;
if (!item) {
// Draw the whole imageViewer
sourceRect = viewer.getViewBounds(true, false);
sourceRectClipped = viewer.getViewBounds(true, true);
}
else {
// Only draw the rect for the active item
sourceRect = viewer.getItemViewBounds(item, lt.Controls.ImageViewerItemPart.image, false);
sourceRectClipped = viewer.getItemViewBounds(item, lt.Controls.ImageViewerItemPart.image, true);
}
const ctx = redirectCanvas.getContext("2d");
ctx.clearRect(0, 0, redirectWidth, redirectHeight);
// Draw a rect around the maximum render area
ctx.strokeStyle = "green";
ctx.strokeRect(destRect.x, destRect.y, destRect.width, destRect.height);
// Create the transformation for this rect
options.createTransform(viewer, destRect, sourceRect, lt.Controls.ControlSizeMode.fit, lt.Controls.ControlAlignment.center, lt.Controls.ControlAlignment.center);
// Draw a rect around the actual render area
const clipRect = options.transform.transformRect(sourceRect);
ctx.strokeStyle = "orange";
ctx.strokeRect(clipRect.x, clipRect.y, clipRect.width, clipRect.height);
// Do the redirect render
viewer.renderRedirect(ctx, options, lt.LeadRectD.empty);
// Show how to draw the item's border
const manuallyComputeRedirectedBorder = () => {
const points = [lt.LeadPointD.create(sourceRectClipped.left, sourceRectClipped.top), lt.LeadPointD.create(sourceRectClipped.right, sourceRectClipped.bottom)];
options.transform.transformPoints(points);
let xmin = points[0].x;
let ymin = points[0].y;
let xmax = xmin;
let ymax = ymin;
for (let i = 1; i < points.length; i++) {
if (points[i].x < xmin) xmin = points[i].x;
if (points[i].x > xmax) xmax = points[i].x;
if (points[i].y < ymin) ymin = points[i].y;
if (points[i].y > ymax) ymax = points[i].y;
}
const bounds = lt.LeadRectD.fromLTRB(xmin, ymin, xmax, ymax);
ctx.strokeStyle = "blue";
ctx.strokeRect(bounds.x, bounds.y, bounds.width, bounds.height);
};
manuallyComputeRedirectedBorder();
});
viewer.invalidate(lt.LeadRectD.empty);
}
}
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 | RenderRedirect</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.RenderRedirect();
};
</script>
</html>
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