模拟背景大小：覆盖 要么

Question

如何background-size:cover在html元素（例如<video>或）上模拟的功能<img>？

我希望它像

background-size: cover;
background-position: center center;

Answer 1

这是我的方法。一个有效的示例在此jsFiddle中。

var min_w = 300; // minimum video width allowed

var vid_w_orig;  // original video dimensions

var vid_h_orig;



jQuery(function() { // runs after DOM has loaded



  vid_w_orig = parseInt(jQuery('video').attr('width'));

  vid_h_orig = parseInt(jQuery('video').attr('height'));

  $('#debug').append("<p>DOM loaded</p>");



  jQuery(window).resize(function () { resizeToCover(); });

  jQuery(window).trigger('resize');

});



function resizeToCover() {

  // set the video viewport to the window size

  jQuery('#video-viewport').width(jQuery(window).width());

  jQuery('#video-viewport').height(jQuery(window).height());



  // use largest scale factor of horizontal/vertical

  var scale_h = jQuery(window).width() / vid_w_orig;

  var scale_v = jQuery(window).height() / vid_h_orig;

  var scale = scale_h > scale_v ? scale_h : scale_v;



  // don't allow scaled width < minimum video width

  if (scale * vid_w_orig < min_w) {scale = min_w / vid_w_orig;};



  // now scale the video

  jQuery('video').width(scale * vid_w_orig);

  jQuery('video').height(scale * vid_h_orig);

  // and center it by scrolling the video viewport

  jQuery('#video-viewport').scrollLeft((jQuery('video').width() - jQuery(window).width()) / 2);

  jQuery('#video-viewport').scrollTop((jQuery('video').height() - jQuery(window).height()) / 2);



  // debug output

  jQuery('#debug').html("<p>win_w: " + jQuery(window).width() + "</p>");

  jQuery('#debug').append("<p>win_h: " + jQuery(window).height() + "</p>");

  jQuery('#debug').append("<p>viewport_w: " + jQuery('#video-viewport').width() + "</p>");

  jQuery('#debug').append("<p>viewport_h: " + jQuery('#video-viewport').height() + "</p>");

  jQuery('#debug').append("<p>video_w: " + jQuery('video').width() + "</p>");

  jQuery('#debug').append("<p>video_h: " + jQuery('video').height() + "</p>");

  jQuery('#debug').append("<p>vid_w_orig: " + vid_w_orig + "</p>");

  jQuery('#debug').append("<p>vid_h_orig: " + vid_h_orig + "</p>");

  jQuery('#debug').append("<p>scale: " + scale + "</p>");

};


#video-viewport {

  position: absolute;

  top: 0;

  overflow: hidden;

  z-index: -1; /* for accessing the video by click */

}



#debug {

  position: absolute;

  top: 0;

  z-index: 100;

  color: #fff;

  font-size: 12pt;

}


<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

<div id="video-viewport">

  <video autoplay controls preload width="640" height="360">

    <source src="http://www.quirksmode.org/html5/videos/big_buck_bunny.mp4"type="video/mp4" />

    <source src="http://www.quirksmode.org/html5/videos/big_buck_bunny.webm"type="video/webm" />

    <source src="http://www.quirksmode.org/html5/videos/big_buck_bunny.ogv"type="video/webm" />

  </video>

</div>



<div id="debug"></div>