ImageCapture
The ImageCapture
interface of the MediaStream Image Capture API provides methods to enable the capture of images or photos from a camera or other photographic device. It provides an interface for capturing images from a photographic device referenced through a valid MediaStreamTrack
.
Constructor
ImageCapture()
-
Creates a new
ImageCapture
object which can be used to capture still frames (photos) from a givenMediaStreamTrack
which represents a video stream.
Properties
ImageCapture.track
Read only-
Returns a reference to the
MediaStreamTrack
passed to the constructor.
Methods
The ImageCapture
interface is based on EventTarget
, so it includes the methods defined by that interface as well as the ones listed below.
ImageCapture.takePhoto()
-
Takes a single exposure using the video capture device sourcing a
MediaStreamTrack
and returns aPromise
that resolves with aBlob
containing the data. ImageCapture.getPhotoCapabilities()
-
Returns a
Promise
that resolves with aPhotoCapabilities
object containing the ranges of available configuration options. ImageCapture.getPhotoSettings()
-
Returns a
Promise
that resolves with aPhotoSettings
object containing the current photo configuration settings. ImageCapture.grabFrame()
-
Takes a snapshot of the live video in a
MediaStreamTrack
, returning anImageBitmap
, if successful.
Example
The following code is taken from Chrome's Grab Frame - Take Photo Sample. Since ImageCapture
requires some place to capture an image from, the example below starts with a device's media device (in other words a camera).
This example shows, roughly, a MediaStreamTrack
extracted from a device's MediaStream
. The track is then used to create an ImageCapture
object so that takePhoto()
and grabFrame()
can be called. Finally, it shows how to apply the results of these calls to a canvas object.
var imageCapture;
function onGetUserMediaButtonClick() {
navigator.mediaDevices.getUserMedia({video: true})
.then(mediaStream => {
document.querySelector('video').srcObject = mediaStream;
const track = mediaStream.getVideoTracks()[0];
imageCapture = new ImageCapture(track);
})
.catch(error => console.log(error));
}
function onGrabFrameButtonClick() {
imageCapture.grabFrame()
.then(imageBitmap => {
const canvas = document.querySelector('#grabFrameCanvas');
drawCanvas(canvas, imageBitmap);
})
.catch(error => console.log(error));
}
function onTakePhotoButtonClick() {
imageCapture.takePhoto()
.then(blob => createImageBitmap(blob))
.then(imageBitmap => {
const canvas = document.querySelector('#takePhotoCanvas');
drawCanvas(canvas, imageBitmap);
})
.catch(error => console.log(error));
}
/* Utils */
function drawCanvas(canvas, img) {
canvas.width = getComputedStyle(canvas).width.split('px')[0];
canvas.height = getComputedStyle(canvas).height.split('px')[0];
let ratio = Math.min(canvas.width / img.width, canvas.height / img.height);
let x = (canvas.width - img.width * ratio) / 2;
let y = (canvas.height - img.height * ratio) / 2;
canvas.getContext('2d').clearRect(0, 0, canvas.width, canvas.height);
canvas.getContext('2d').drawImage(img, 0, 0, img.width, img.height,
x, y, img.width * ratio, img.height * ratio);
}
document.querySelector('video').addEventListener('play', function() {
document.querySelector('#grabFrameButton').disabled = false;
document.querySelector('#takePhotoButton').disabled = false;
});
Specifications
Specification |
---|
MediaStream Image Capture # imagecaptureapi |
Browser compatibility
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