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ReactJS canvas drawImage 不显示 html5 视频元素

[英]ReactJS canvas drawImage without showing html5 video element

I need to draw the stream from camera on top of a canvas using drawImage, however when I add the video element in react component it shows the element's stream in the page too.我需要使用drawImage从canvas顶部的摄像头绘制stream,但是当我在react组件中添加视频元素时,它也会在页面中显示元素的stream。 If I use display:'none' drawImage can't draw the user's webcam, it draws blank screen.如果我使用 display:'none' drawImage 无法绘制用户的网络摄像头,它会绘制空白屏幕。 Do I have to show html5 video element in the page or is there a way to play it without showing?我是否必须在页面中显示 html5 视频元素,或者有没有办法在不显示的情况下播放它?

I am getting video stream from camera with getUserMedia:我正在使用 getUserMedia 从相机获取视频 stream:

async function getCameraStream() {
      try {
        const constraint = { video: true }
        const stream = await navigator.mediaDevices.getUserMedia(constraint)
        if (videoRef.current) {
          videoRef.current.srcObject = stream
          return
        }
      } catch (error) {
        console.error('Error opening video camera.', error)
      }
      setLoading(false)
      setCameraError(true)
    }

And the video ref is:视频参考是:

  return(  <video 
              style={{display: 'none' }}
              ref={videoRef}
              className={classes.sourcePlayback}
              src={sourceUrl}
              hidden={isLoading}
              autoPlay
              playsInline
              controls={false}
              muted
              loop
              onLoadedData={handleVideoLoad}
            />)

I am using this videoRef in canvas like:我在 canvas 中使用这个 videoRef 像:

ctx.drawImage(sourcePlayback.htmlElement, 0, 0)

Here if the htmlElement is given with display:'none' it doesn't draw.在这里,如果 htmlElement 与 display:'none' 一起给出,则它不会绘制。 I want to draw the htmlElement but not show it in the page.Is there a way to achieve this?我想绘制 htmlElement 但不在页面中显示它。有没有办法实现这一点? I want html5VideoElement to play invisibly basically.display:none does not work.我希望 html5VideoElement 基本上不可见地播放。display:none 不起作用。

EDIT:编辑:

Add css as visibility:'hidden' works for this one.添加 css 作为可见性:“隐藏”适用于此。

sourcePlayback: {
      visibility: 'hidden',
      display: 'flex',
      width: 0,
      height: 0,
    },

I was able to replicate your issue in chrome with https://record.a.video .我能够使用https://record.a.video在 chrome 中复制您的问题。

When I used display: none on the video attribute, the video overlay on the canvas was black instead of my camera.当我在视频属性上使用display: none时,canvas 上的视频覆盖是黑色的,而不是我的相机。

Workaround:解决方法:

When I set the CSS on the video to width:1px , the video shows up on the canvas.当我将视频上的 CSS 设置为width:1px时,视频会显示在 canvas 上。 I suppose it's technically on the screen, but it'll probably work for your purposes.我想它在技术上是在屏幕上,但它可能会为你的目的工作。

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