Image with are selection

Note. The task interface configuration guide describes the features of the HTML/JS/CSS editor. You can also try creating a task interface in the Template Builder.

The editor lets you select an area of the image using either a rectangle or an arbitrary polygon:

Note. Don't add training or control tasks in the project that features image area selection editor.

Adding the editor

If you need to add an image editor without selected objects:

  1. Connect the $TOLOKA_ASSETS/js/image-annotation.js library (click in the Task interface block on the project page).

  2. Include the {{field type="image-annotation" name="<output field name>" src=<image URL>}} component in the HTML code of the interface. Example:

    {{field type="image-annotation" name="result" src=image}}

    For a complete list of parameters, see the table.

  3. Add a field for entering an image link in the input data. If you store images on Yandex.Disk, use the string type, not link.
  4. Add the result with the json type in the output data.

The result field will be used for a JSON object with the point coordinates. Example:


The x and y values are numbers from 0 to 1. Length and width of the image are taken as 1, with the center of coordinates in the upper-left corner of the image.





Default value

Field type: image-annotation, the image area selection editor.




Attribute for the output data field. Contains the output field name.




Image URL. Supported values:

  • URL from the input data of the task. For example, from the field with the url: src=image ID.

  • Direct link. The HTTPS protocol is recommended. For example, src="".

  • Relative link. If you use files on Yandex.Disk, specify the proxy component and the name of the input data field. For example, for a field with the name image write src=(proxy image). Change the field type to string.




Attribute for the input data field. Contains the input data field name. Here you can pass the selection coordinates for further editing. The data format is a JSON object.




By default, you can use the following keyboard shortcuts in the task:
  • C closes a polygon connecting the first and last points with a line.
  • D deletes the selected point, selected object or last point when creating the polygon.
  • Arrows move the selected point. With Alt pressed, they move it slower. With Alt+Shift pressed, they move it faster.
  • Tab moves from the selected point to the next one.
  • Shift+Tab moves from the selected point to the previous one.

Tell performers about keyboard shortcuts in the instructions to speed up task completion.

Selection tools

By default, rectangle tool is added to the task interface.

You can change the tools set:

To add a rectangle, delete the CSS selector:
.image-annotation-editor__shape-rectangle {
  display: none;


To use annotations, insert one of these examples in the JS block:

exports.Task = extend(TolokaHandlebarsTask, function (options) {, options);
}, {
    onRender: function() {
        var field = this.getField('result');
        var editor = field.getEditor();
        editor.annotationInterface = field.createAnnotationInterface({
            createInterfaceElement: function() {
                this._input = document.createElement('input');
                this._input.addEventListener('input', function() {
                    this._shape.annotation = this._input.value;
                return this._input;
            onShow: function(shape) {
                this._shape = shape;
                this._input.value = shape.annotation;
  onDestroy: function() {
    // Task is completed. Global resources can be released (if used)

function extend(ParentClass, constructorFunction, prototypeHash) {
  constructorFunction = constructorFunction || function () {};
  prototypeHash = prototypeHash || {};
  if (ParentClass) {
    constructorFunction.prototype = Object.create(ParentClass.prototype);
  for (var i in prototypeHash) {
    constructorFunction.prototype[i] = prototypeHash[i];
  return constructorFunction;
Explanation of examples

To let the performer enter annotation for the selected area or choose it from the list, add an interface element to the task (for example, a text field or a drop-down list):

  1. Get the editor object getEditor() and annotation interface getField('result') in the onRender() method:

    var field = this.getField('result');    
    var editor = field.getEditor();
  2. Implement the annotation interface in these methods:
    • createInterfaceElement() — Calls the interface DOM element (the method is called once during the initialization of the object).

    • onShow(shape, options) — Displays the annotation interface element when the performer points the mouse at the selected area. Accepts JSON with polygon point coordinates. This JSON can also be used to save annotations entered by the performer.

The following events occur when the performer interacts with the editor:

  • shape:start — Start of area selection.

  • shape:finish — End of area selection.

  • shape:cancel — Removal of a polygon point.

  • shape:remove — Removal of area selection.

To subscribe to these events:

editor.on('shape:start', function() {
    /* event handling */