OpenSeadragonImagingHelper
OpenSeadragonImagingHelper is a plugin for OpenSeadragon
which implements some properties and methods helpful in
imaging applications.
View the Documentation
Demo/Test Site
Usage
Prerequisite note: OpenSeadragonImagingHelper requires OpenSeadragon version 2.0+.
The OpenSeadragonImagingHelper bundle can be obtained the following ways:
- Direct download openseadragon-imaginghelper.js (and optionally openseadragon-imaginghelper.js.map)
- npm
npm install @openseadragon-imaging/openseadragon-imaginghelper
The OpenSeadragonImagingHelper bundle can be included using a script tag in HTML or imported as a library module (ES2015, CommonJS, AMD).
An ImagingHelper object can be created and attached to an OpenSeadragon.Viewer two ways:
- Call the activateImagingHelper method on the viewer
- Create a new ImagingHelper object, passing a viewer reference in the options parameter
Both methods return a new ImagingHelper object, and both methods also add the ImagingHelper
object reference to the viewer as a property called 'imagingHelper'.
Example using an HTML script tag
<script
type="text/javascript"
src="path_to/openseadragon/openseadragon.js"
></script>
<script
type="text/javascript"
src="path_to/openseadragon-imaging/openseadragon-imaginghelper.js"
></script>
var viewer = window.OpenSeadragon({...});
var imagingHelper = viewer.activateImagingHelper({...});
var imagingHelper = new window.OpenSeadragonImaging.ImagingHelper({viewer: existingviewer});
Example importing as a module
npm install openseadragon --save
npm install @openseadragon-imaging/openseadragon-imaginghelper --save
import OpenSeadragon from 'openseadragon';
import OpenSeadragonImagingHelper from '@openseadragon-imaging/openseadragon-imaginghelper';
var viewer = OpenSeadragon({...});
var imagingHelper = viewer.activateImagingHelper({...});
var imagingHelper = new OpenSeadragonImagingHelper({viewer: existingviewer});
Details
The ImagingHelper class provides a simplified zoomFactor which is simply the ratio
of the displayed image pixel size to the image's native pixel size.
In OpenSeadragon 2.0 and above, conversion is based on the image at index 0 in world.getItemAt, unless another value is set by the worldIndex option.
The ImagingHelper methods use three coordinate systems,
named as follows:
- physical: Device pixel coordinates relative to the SeaDragon viewer
- logical: 0.0 to 1.0 relative to the image's native dimensions
- data: Pixel coordinates relative to the image's native dimensions
Methods are provided to zoom and/or pan using these conventions, as well as to convert
individual horizontal/vertical values or point ({x,y}) objects between coordinate systems
(Note: methods that return a point object return new OpenSeadragon.Point
objects)
The ImagingHelper class extends the OpenSeadragon.EventSource class and raises
an event named 'image-view-changed' whenever the viewer's zoom and/or pan position changes.
var viewer = OpenSeadragon({...});
var imagingHelper = viewer.activateImagingHelper({onImageViewChanged: onImageViewChanged});
function onImageViewChanged(event) {
...
}
imagingHelper.addHandler('image-view-changed', function (event) {
...
});
Demo/Test Site
The demo site is an example using ImagingHelper in a React application.
The page displays many OpenSeadragon and OpenSeadragonImagingHelper metrics, as well as the output of many OpenSeadragonImagingHelper methods, all in real-time as the cursor moves and/or the image is zoomed/panned.
The source code can be found here.
Legacy Demo/Test Site
The old demo site is still available here.
This page adds an example of syncing an SVG overlay for annotation support.
All the sample code is in scripts/viewmodel.js.
TODO
- Better multi-image support