Javascript 如何在Firefox中实现基于视频约束的getusermedia捕获？在Chrome中，一切都是按照代码进行的，而不是Firefox？

当我想从getusermedia捕获图像时，我遇到了一个问题，Firefox中捕获的图像没有保留我在视频约束中设置的比率。 这是获取视频的比率，但从我所看到的视频来看，它没有考虑Firefox中的限制

if(navigator.mediaDevices && navigator.mediaDevices.getUserMedia) {
        if(window.innerWidth >= 600){
          this.canvasWidth = 480;
          this.canvasHeight = 360;
        } else {
          this.canvasWidth = 240;
          this.canvasHeight = 240;
        }
        navigator.mediaDevices.getUserMedia({ audio: false,video: {facingMode: 'user', width: this.canvasWidth * 2, height: this.canvasHeight * 2} }).then(stream => {
            this.useWebcam = true;
            this.canvas.nativeElement.style.display = 'none';
            this.video.nativeElement.srcObject = stream;
            this.stream = stream;
            this.ref.detectChanges();
            this.video.nativeElement.play();
            console.log(stream);
        }).catch(reason => {
          this.useWebcam = false;
          if(this.acceptable){
            this.acceptable = false;
            this.eMessage = reason + "<br/>Please check your camera to continue.";
            this.ref.detectChanges();
          }
          // alert(reason + " \nPlease check your camera to continue.")
        });
      } else {
        this.eMessage = "Please check your camera to continue.";
      }

如何使用给定的约束制作视频？这段代码在Chrome中有效，而不是在Firefox中？多谢各位

注:

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在提问之前，我已经阅读了其他问题，但仍然没有回答我的问题。谢谢

您向getUserMedia（）提供的约束是请求。你不会总是得到你要求的准确尺寸

我同意你的观察，Google Chrome比Firefox更符合你的要求。我尝试使用

exact

属性强制Firefox使用精确维度，但它拒绝了，并出现了一个违反约束的错误

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我必须剪辑捕获的Firefox图像，使其与我在Chrome中捕获的图像大小相同。为了让抓拍的用户看起来更合适，我还安排了一些CSS来剪辑预览窗口。

最后，在试用了我的代码之后，我可以进行预览

positioningVideo(){
    //Check Orientation
    if(this.videoWidth > this.videoHeight){
      let temp = this.videoWidth;
      this.videoWidth = this.videoHeight;
      this.videoHeight = temp;
    }

    if(this.videoWidth > (this.canvasWidth * 2)){
      this.video.nativeElement.style.maxHeight = '' + this.canvasHeight + 'px' ;
      this.video.nativeElement.style.maxWidth = '' + (this.videoWidth / 2) + 'px';
    } else if(this.videoHeight > (this.canvasHeight * 2)){
      this.video.nativeElement.style.maxWidth = '' + this.canvasWidth + 'px' ;
      this.video.nativeElement.style.maxHeight = '' + (this.videoHeight / 2) + 'px';
    } else if(this.videoWidth == (this.canvasWidth * 2) && this.videoHeight == (this.canvasHeight * 2)){
      this.video.nativeElement.style.maxHeight = '' + this.canvasHeight + 'px' ;
      this.video.nativeElement.style.maxWidth = '' + this.canvasWidth + 'px' ;
    }

  }

我用一些计算来设置我的起始坐标

注意：我使用的是裁剪中心，因此我计算顶部或左侧的边距

capture() {
    let coorX = 0, coorY = 0;
    
    if(this.videoWidth != (this.canvasWidth * 2)){
      coorX = (this.videoWidth - (this.canvasWidth * 2)) / 2;
    }
    if(this.videoHeight != (this.canvasHeight * 2)){
      coorY = (this.videoHeight - (this.canvasHeight * 2)) / 2;
    }
    this.canvas.nativeElement.style.display = 'block';
    this.canvas.nativeElement.getContext("2d").scale(-1,1);
    this.canvas.nativeElement.getContext("2d").drawImage(this.video.nativeElement, coorX, coorY, this.canvasWidth * 2, this.canvasHeight * 2, 0, 0, -1 * this.canvasWidth, this.canvasHeight);
    this.canvas.nativeElement.getContext("2d").restore();
    this.captured = this.canvas.nativeElement.toDataURL("image/png");
    this.video.nativeElement.parentElement.style.display = 'none';
  }

capture() {
    let coorX = 0, coorY = 0;
    
    if(this.videoWidth != (this.canvasWidth * 2)){
      coorX = (this.videoWidth - (this.canvasWidth * 2)) / 2;
    }
    if(this.videoHeight != (this.canvasHeight * 2)){
      coorY = (this.videoHeight - (this.canvasHeight * 2)) / 2;
    }
    this.canvas.nativeElement.style.display = 'block';
    this.canvas.nativeElement.getContext("2d").scale(-1,1);
    this.canvas.nativeElement.getContext("2d").drawImage(this.video.nativeElement, coorX, coorY, this.canvasWidth * 2, this.canvasHeight * 2, 0, 0, -1 * this.canvasWidth, this.canvasHeight);
    this.canvas.nativeElement.getContext("2d").restore();
    this.captured = this.canvas.nativeElement.toDataURL("image/png");
    this.video.nativeElement.parentElement.style.display = 'none';
  }