Create thumbnail from video file via file input

问题

I am attempting to create a thumbnail preview from a video file (mp4,3gp) from a form input type='file'. Many have said that this can be done server side only. I find this hard to believe since I just recently came across this Fiddle using HTML5 Canvas and Javascript.

Thumbnail Fiddle

The only problem is this requires the video to be present and the user to click play before they click a button to capture the thumbnail. I am wondering if there is a way to get the same results without the player being present and user clicking the button. For example: User click on file upload and selects video file and then thumbnail is generated. Any help/thoughts are welcome!

回答1:

Canvas.drawImage must be based on html content.

source

here is a simplier jsfiddle

//and code
function capture(){
    var canvas = document.getElementById('canvas');
    var video = document.getElementById('video');
    canvas.getContext('2d').drawImage(video, 0, 0, video.videoWidth, video.videoHeight);
}

The advantage of this solution is that you can select the thumbnail you want based on the time of the video.

回答2:

Recently needed this and did quite some testing and boiling it down to the bare minimum, see https://codepen.io/aertmann/pen/mAVaPx

There are some limitations where it works, but fairly good browser support currently: Chrome, Firefox, Safari, Opera, IE10, IE11, Android (Chrome), iOS Safari (10+).

 video.preload = 'metadata';
 video.src = url;
 // Load video in Safari / IE11
 video.muted = true;
 video.playsInline = true;
 video.play();

来源：https://stackoverflow.com/questions/23640869/create-thumbnail-from-video-file-via-file-input