CropTarget: fromElement() static method

Limited availabilitySecure context

The fromElement() static method of the CropTarget interface returns a CropTarget instance that can be used to crop a captured video track to the area in which a specified element is rendered.

Because the Region Capture API crops to an area of the current browser tab rather than capturing a specific element, any content drawn on top of the cropped area will be shown in the capture.

Syntax

CropTarget.fromElement(element)

Parameters

• element

  • : A reference to an Element that you want to use as a crop target. For an element to be used as a crop target, it must be:

    • On-screen
    • Visible, that is, not hidden via display: none for example.

    In addition, the element will not be captured if the track being restricted has clones (that is, created by clone()) or is captured from a different tab to the current user’s tab (passed via postMessage(), for example).

Return value

A Promise that resolves to a CropTarget object instance, which can then be passed to CropTo() to crop the video captured in the track to just the area the specified DOM element is rendered in.

CropTarget objects are serializable. They can be passed to another document using mechanisms such as postMessage().

Examples

// Options for getDisplayMedia()
const displayMediaOptions = {
  preferCurrentTab: true,
};

// Create crop target from DOM element
const demoElem = document.querySelector("#demo");
const cropTarget = await CropTarget.fromElement(demoElem);

// Capture video stream from user's webcam and isolate video track
const stream =
  await navigator.mediaDevices.getDisplayMedia(displayMediaOptions);
const [track] = stream.getVideoTracks();

// Crop video track
await track.cropTo(cropTarget);

// Broadcast cropped stream in <video> element
videoElem.srcObject = stream;

See Using the Element Capture and Region Capture APIs for in-context example code.

Specifications

Browser compatibility

See also

• Screen Capture API
• Using the Element Capture and Region Capture APIs