问题描述
当我想从getusermedia捕获图像时出现问题,在Firefox中捕获的图像没有保持我在视频限制中设置的比例。 这是获取视频的比率,但是从我看到的视频来看,Firefox没有受到限制
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.";
}
这是用于拍照并重新拍照
capture() {
this.canvas.nativeElement.style.display = 'block';
this.canvas.nativeElement.getContext("2d").scale(-1,1);
this.canvas.nativeElement.getContext("2d").drawImage(this.video.nativeElement,this.canvas.nativeElement.width * 2,this.canvas.nativeElement.height * 2,-1 * this.canvas.nativeElement.width,this.canvas.nativeElement.height);
this.canvas.nativeElement.getContext("2d").restore();
this.captured = this.canvas.nativeElement.toDataURL("image/png");
this.video.nativeElement.style.display = 'none';
}
retake() {
setTimeout(() => {
this.canvas.nativeElement.getContext("2d").scale(-1,1);
this.canvas.nativeElement.getContext("2d").clearRect(0,this.canvas.nativeElement.height);
this.canvas.nativeElement.getContext("2d").restore();
this.canvas.nativeElement.style.display = 'none';
this.video.nativeElement.style.display = 'block';
this.captured = null;
},20);
}
如何使用给定的约束制作视频?这段代码在Chrome中有效,在Firefox中无效?谢谢
注意: 在询问之前,我已经阅读了其他问题,但对于我的案子仍然没有答案。谢谢
解决方法
呈现给getUserMedia()的约束是请求。您将无法始终获得所需的确切尺寸。
我同意您的看法,即Google Chrome浏览器比Firefox更符合您要求的尺寸。我尝试通过exact
属性强制Firefox使用确切的尺寸,但是由于约束冲突错误而被拒绝。
我必须裁剪捕获的Firefox图像,使其大小与我在Chrome中捕获的图像大小相同。为了使用户在进行捕获时看起来合适,我还安排了一些CSS,以裁剪预览窗口。
,最后,在尝试了我的代码之后,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:我正在使用作物中心,所以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,-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';
}