marker.js is a JavaScript library to enable image annotation in your web projects. Users can annotate and mark up images, and you can save, share or otherwise process the results.
npm install markerjs
To enable image annotation in your project follow these 3 simple steps:
- Attach
markerjs.MarkerAreato the image; - Pass a callback method to the
MarkerArea.show()method; - Process the results when the user is done.
import { MarkerArea } from 'markerjs';
const m = new MarkerArea(document.getElementById('imageToAnnotate'));
m.show(
(dataUrl) => {
const res = document.getElementById("resultImage");
res.src = dataUrl;
}
);Starting with version 1.2 marker.js accepts a second parameter to the MarkerArea constructor. You can pass configuration through that object parameter.
Currently supported configuration settings are:
targetRoot- in case your target image is not a child ofdocument.bodyyou can specify a different root here,renderAtNaturalSize- set totrueto render the resulting marked image at the native resolution of the source target image,markerColors- object with color values for markers:mainColor- main color for most markers (default: #ff0000),highlightColor- color for theHighlightMarker- will be displayed semi-transparent,coverColor- color for theCoverMarker,
strokeWidth(new in 1.7) - set width of the stroke (line) on rectangular, ellipse and line markers (default: 3);renderImageType(new in 1.4) - marker.js renders in PNG by default but you can change this to other MIME type if you like (like "image/jpeg"),renderImageQuality(new in 1.4) - in a lossy image type (like JPEG) controls image quality (number from 0 to 1),renderMarkersOnly(new in 1.5) - renders the markers layer only (without the original image) when set totrue. Note: make surerenderImageTypeisimage/png(default) if you want to get transparent background image that can be overlayed on the original,previousState(new in 1.6) - lets you pass a state from a previous annotation session to continue editing (see "Multi-session example" for details).
This example sets marker.js to render at original image resolution and chages the main marker color to green.
const m = new MarkerArea(document.getElementById('imageToAnnotate'), {
renderAtNaturalSize: true,
markerColors: {
mainColor: '#00cc00'
}
});You don't have to use marker.js with its built-in toolbar. It's perfectly understandable that often you'd rather integrate annotation functionality into your own UI. And you may also want to limit available marker types according to your requirements.
marker.js has you covered. Instead of calling MarkerArea.show() like described above, call MarkerArea.open(), then call one of the following methods from your UI to perform whatever action you are after:
addMarker(markerType)- calladdMarkerto place a new marker of themarkerTypetype into the marker area. Currently supported marker types are:ArrowMarker- arrows,CoverMarker- solid rectangle to cover areas you'd rather not show,EllipseMarker(new in v.1.3) - transparent ellipse with solid border,HighlightMarker- semi-transparent rectangle to highlight areas,LineMarker- lines,RectMarker- transparent rectangle with solid border,TextMarker- text;
deleteActiveMarker()- deletes currently selected marker (if any);render(completeCallback)- renders current marker area on top of the original image and calls acompleteCallbackwhen done passing adataUrlrepresenting the resulting image. This can then be used for whatever you want to do wit the result;close()- call when you are done and want to remove marking functionality from the image.
This example assumes that marker.js was included in the page via a script tag ala:
<script src="https://unpkg.com/markerjs"></script>And has this simplistic toolbar to control marker.js behavior:
<div id="markerActivator">
<button onclick="showApiMarker(document.getElementById('targetImage'));">mark</button>
</div>
<div id="markerControls" style="display: none;">
<button onclick="addArrow();">add arrow</button>
<button onclick="deleteMarker();">delete marker</button>
<button onclick="render();">render</button>
<button onclick="closeMarkerArea();">close</button>
</div>Note that for this example we want to support arrow markers only.
So, our JavaScript code would look something like this:
let markerArea;
function showApiMarker(img) {
markerArea = new markerjs.MarkerArea(img);
markerArea.open();
document.getElementById('markerActivator').style.display = 'none';
document.getElementById('markerControls').style.display = '';
}
function addArrow() {
if (markerArea) {
markerArea.addMarker(markerjs.ArrowMarker);
}
}
function deleteMarker() {
if (markerArea) {
markerArea.deleteActiveMarker();
}
}
function render() {
if (markerArea) {
markerArea.render((dataUrl) => {
const res = document.getElementById("resultImage");
res.src = dataUrl;
res.style.display = "";
});
}
}
function closeMarkerArea() {
if (markerArea) {
markerArea.close();
}
document.getElementById('markerActivator').style.display = '';
document.getElementById('markerControls').style.display = 'none';
}Starting with version 1.6 you can save and restore the previous annotation session. The state is returned on each render as the second argument to completeCallback and then you can pass it back in the config to the constructor of a new MarkerArea.
let savedState;
const m = new MarkerArea(document.getElementById('imageToAnnotate'), {
previousState: savedState
});
m.show(
(dataUrl, state) => {
const res = document.getElementById("resultImage");
res.src = dataUrl;
savedState = state;
}
);This way in every subsequent editing session the state will be restored. You can persist this state in your app as JSON and restore later on.
marker.js is using Font Awesome Free icons for the toolbar UI.
Since version 1.8 marker.js is released under the MIT license.
The annotation UI includes a small logo back to marker.js website. You can find instructions on how to remove it here.