是否可以在画布中显示html5-video?
与在画布中绘制图像的方式基本相同。
context.drawVideo(vid, 0, 0);
谢谢!
答案 0 :(得分:61)
var canvas = document.getElementById('canvas');
var ctx = canvas.getContext('2d');
var video = document.getElementById('video');
video.addEventListener('play', function () {
var $this = this; //cache
(function loop() {
if (!$this.paused && !$this.ended) {
ctx.drawImage($this, 0, 0);
setTimeout(loop, 1000 / 30); // drawing at 30fps
}
})();
}, 0);
我猜上面的代码是自我解释的,如果不在下面发表评论,我会尝试解释以上几行代码
修改:
这是一个在线示例,仅供您使用:)
的 Demo 强>
var canvas = document.getElementById('canvas');
var ctx = canvas.getContext('2d');
var video = document.getElementById('video');
// set canvas size = video size when known
video.addEventListener('loadedmetadata', function() {
canvas.width = video.videoWidth;
canvas.height = video.videoHeight;
});
video.addEventListener('play', function() {
var $this = this; //cache
(function loop() {
if (!$this.paused && !$this.ended) {
ctx.drawImage($this, 0, 0);
setTimeout(loop, 1000 / 30); // drawing at 30fps
}
})();
}, 0);
<div id="theater">
<video id="video" src="http://upload.wikimedia.org/wikipedia/commons/7/79/Big_Buck_Bunny_small.ogv" controls="false"></video>
<canvas id="canvas"></canvas>
<label>
<br />Try to play me :)</label>
<br />
</div>
答案 1 :(得分:25)
显示视频与显示图像非常相似。微小差异与onload事件有关,以及你需要每帧渲染视频的事实,或者你只能看到一帧而不是动画帧。
下面的演示与示例有一些细微差别。一个静音功能(在视频点击静音/声音开启以切换声音)和一些错误检查,以捕获IE9 +和Edge,如果他们没有正确的驱动程序。
保持最新答案。 user372551 以前的答案已过时(2010年12月),并且在使用的渲染技术方面存在缺陷。它使用setTimeout
和33.333 ...的速率,其中setTimeout将向下舍入到33ms,这将导致帧每两秒丢弃一次,如果视频帧速率高于30,则可能会下降更多。使用setTimeout
还会引入视频剪切,因为setTimeout无法同步到显示硬件。
目前还没有可靠的方法可以确定视频帧速率,除非您事先知道视频帧速率,否则应以浏览器可能的最大显示刷新率显示它。 60fps的
给出的最佳答案是时间(6年前)最佳解决方案requestAnimationFrame
没有被广泛支持(如果有的话),但requestAnimationFrame
现在是主要浏览器的标准,应该是用来代替setTimeout来减少或删除丢帧,并防止剪切。
加载视频并将其设置为循环播放。直到您点击它才会播放视频。再次单击将暂停。视频下方的按钮上有静音/声音。视频默认为静音。
注意IE9 +和Edge的用户。您可能无法播放视频格式WebM,因为它需要其他驱动程序才能播放视频。可以在 tools.google.com Download IE9+ WebM support
找到它们
// This code is from the example document on stackoverflow documentation. See HTML for link to the example.
// This code is almost identical to the example. Mute has been added and a media source. Also added some error handling in case the media load fails and a link to fix IE9+ and Edge support.
// Code by Blindman67.
// Original source has returns 404
// var mediaSource = "http://video.webmfiles.org/big-buck-bunny_trailer.webm";
// New source from wiki commons. Attribution in the leading credits.
var mediaSource = "http://upload.wikimedia.org/wikipedia/commons/7/79/Big_Buck_Bunny_small.ogv"
var muted = true;
var canvas = document.getElementById("myCanvas"); // get the canvas from the page
var ctx = canvas.getContext("2d");
var videoContainer; // object to hold video and associated info
var video = document.createElement("video"); // create a video element
video.src = mediaSource;
// the video will now begin to load.
// As some additional info is needed we will place the video in a
// containing object for convenience
video.autoPlay = false; // ensure that the video does not auto play
video.loop = true; // set the video to loop.
video.muted = muted;
videoContainer = { // we will add properties as needed
video : video,
ready : false,
};
// To handle errors. This is not part of the example at the moment. Just fixing for Edge that did not like the ogv format video
video.onerror = function(e){
document.body.removeChild(canvas);
document.body.innerHTML += "<h2>There is a problem loading the video</h2><br>";
document.body.innerHTML += "Users of IE9+ , the browser does not support WebM videos used by this demo";
document.body.innerHTML += "<br><a href='https://tools.google.com/dlpage/webmmf/'> Download IE9+ WebM support</a> from tools.google.com<br> this includes Edge and Windows 10";
}
video.oncanplay = readyToPlayVideo; // set the event to the play function that
// can be found below
function readyToPlayVideo(event){ // this is a referance to the video
// the video may not match the canvas size so find a scale to fit
videoContainer.scale = Math.min(
canvas.width / this.videoWidth,
canvas.height / this.videoHeight);
videoContainer.ready = true;
// the video can be played so hand it off to the display function
requestAnimationFrame(updateCanvas);
// add instruction
document.getElementById("playPause").textContent = "Click video to play/pause.";
document.querySelector(".mute").textContent = "Mute";
}
function updateCanvas(){
ctx.clearRect(0,0,canvas.width,canvas.height);
// only draw if loaded and ready
if(videoContainer !== undefined && videoContainer.ready){
// find the top left of the video on the canvas
video.muted = muted;
var scale = videoContainer.scale;
var vidH = videoContainer.video.videoHeight;
var vidW = videoContainer.video.videoWidth;
var top = canvas.height / 2 - (vidH /2 ) * scale;
var left = canvas.width / 2 - (vidW /2 ) * scale;
// now just draw the video the correct size
ctx.drawImage(videoContainer.video, left, top, vidW * scale, vidH * scale);
if(videoContainer.video.paused){ // if not playing show the paused screen
drawPayIcon();
}
}
// all done for display
// request the next frame in 1/60th of a second
requestAnimationFrame(updateCanvas);
}
function drawPayIcon(){
ctx.fillStyle = "black"; // darken display
ctx.globalAlpha = 0.5;
ctx.fillRect(0,0,canvas.width,canvas.height);
ctx.fillStyle = "#DDD"; // colour of play icon
ctx.globalAlpha = 0.75; // partly transparent
ctx.beginPath(); // create the path for the icon
var size = (canvas.height / 2) * 0.5; // the size of the icon
ctx.moveTo(canvas.width/2 + size/2, canvas.height / 2); // start at the pointy end
ctx.lineTo(canvas.width/2 - size/2, canvas.height / 2 + size);
ctx.lineTo(canvas.width/2 - size/2, canvas.height / 2 - size);
ctx.closePath();
ctx.fill();
ctx.globalAlpha = 1; // restore alpha
}
function playPauseClick(){
if(videoContainer !== undefined && videoContainer.ready){
if(videoContainer.video.paused){
videoContainer.video.play();
}else{
videoContainer.video.pause();
}
}
}
function videoMute(){
muted = !muted;
if(muted){
document.querySelector(".mute").textContent = "Mute";
}else{
document.querySelector(".mute").textContent= "Sound on";
}
}
// register the event
canvas.addEventListener("click",playPauseClick);
document.querySelector(".mute").addEventListener("click",videoMute)
body {
font :14px arial;
text-align : center;
background : #36A;
}
h2 {
color : white;
}
canvas {
border : 10px white solid;
cursor : pointer;
}
a {
color : #F93;
}
.mute {
cursor : pointer;
display: initial;
}
<h2>Basic Video & canvas example</h2>
<p>Code example from Stackoverflow Documentation HTML5-Canvas<br>
<a href="https://stackoverflow.com/documentation/html5-canvas/3689/media-types-and-the-canvas/14974/basic-loading-and-playing-a-video-on-the-canvas#t=201607271638099201116">Basic loading and playing a video on the canvas</a></p>
<canvas id="myCanvas" width = "532" height ="300" ></canvas><br>
<h3><div id = "playPause">Loading content.</div></h3>
<div class="mute"></div><br>
<div style="font-size:small">Attribution in the leading credits.</div><br>
使用画布渲染视频为您提供了有关在fx中显示和混合的其他选项。下图显示了使用画布可以获得的一些FX。使用2D API可提供广泛的创作可能性。
与回答Fade canvas video from greyscale to color相关的图片
请参阅上面演示中的视频标题,了解上述图片中内容的归属。
答案 2 :(得分:13)
我想提供一种使用更现代语法的解决方案,并且比已经提供的解决方案更简洁:
const canvas = document.querySelector("canvas");
const ctx = canvas.getContext("2d");
const video = document.querySelector("video");
video.addEventListener('play', () => {
function step() {
ctx.drawImage(video, 0, 0, canvas.width, canvas.height)
requestAnimationFrame(step)
}
requestAnimationFrame(step);
})
一些有用的链接:
答案 3 :(得分:0)
您需要更新currentTime视频元素,然后在画布中绘制帧。不要在视频上初始化play()事件。
您也可以使用ex。这个插件https://github.com/tstabla/stVideo