Wenn ich versuche, einen Screenshot zu erstellen und als PNG zu speichern, bevor ich ein Video auf den Server hochlade, tritt das folgende Problem auf:

Ich hoffe du kannst mein Problem lösen ...

/*Output image show view*/
$('#file_browse').change(function(e){
    getVideo(this);
});

var capbtn = document.querySelector('#video_capture');
var video = document.querySelector('video');
var canvas = document.querySelector('canvas');
var context = canvas.getContext('2d');
var w, h, ratio;

video.addEventListener('loadedmetadata', function() {
    ratio = video.videoWidth / video.videoHeight;
    w = video.videoWidth - 100;
    h = parseInt(w / ratio, 10);
    canvas.width = w;
    canvas.height = h;           
}, false);

capbtn.addEventListener("click", function(){
    context.fillRect(0, 0, w, h);
    context.drawImage(video, 0, 0, w, h);
    var objImageData = canvas.toDataURL("data:image/png;");  
});

function getVideo(input) {
    if (input.files && input.files[0]) {
        var reader = new FileReader();
        reader.onload = function (e) {
            var video = document.getElementsByTagName('video')[0];
            var sources = video.getElementsByTagName('source');
            sources[0].src = e.target.result;
            video.load();
            video.style.display="block";
        }
        reader.readAsDataURL(input.files[0]);
    }
}

<input id="video_capture" type="submit" value="Capture" />
<video id="video_view" controls>
    <source src="movie.mp4" type="video/mp4">
</video>
<canvas width="300" height="300"></canvas>