[英]Make screenshot from a video with canvas overlay
我有一个带有一对兄弟画布的html5视频,在上面有一些效果。 结构是这样的:
<div id="container_video">
<video id="video1" width="450" height="340" preload="auto"></video>
<canvas id="overlay" width="450" height="340"></canvas>
<canvas id="webgl" width="450" height="340"></canvas>
</div>
我想从整个场景(带有覆盖画布的视频)中制作快照。 我只能捕捉视频,而不能捕捉整个场景。
我能做什么?
谢谢。
<video id="video1" width="450" height="340" preload="auto"></video>
<canvas id="overlay" width="450" height="340"></canvas>
<canvas id="webgl" width="450" height="340"></canvas>
canvas = document.createElement("canvas");
canvas.width = 450;
canvas.height = 340;
var ctx = canvas.getContext("2d");
var vid = document.getElementById("video1");
var over = document.getElementById("overlay");
var gl = document.getElementById("webgl");
ctx.drawImage(vid,0,0);
ctx.drawImage(over,0,0);
ctx.drawImage(gl,0,0);
// canvas now contains the 3 elements as one image.
您将必须检查视频是否已加载,并在所需的搜索位置。
@ Blindman67它不起作用
如果执行此操作,则出现下一个错误:
TypeError: canvas.getContext is not a function in
var ctx = canvas.getContext("2d");
我尝试另一种方式,如下所示:
var ctx_full = document.getElementById("canvas_full");
ctx = ctx_full.getContext("2d");
var vid = document.getElementById("video1");
var over = document.getElementById("overlay");
var gl = document.getElementById("webgl");
ctx.drawImage(vid,0,0);
ctx.drawImage(over,0,0);
ctx.drawImage(gl,0,0);
然后我出现了错误“ TypeError:
Argument 1 of CanvasRenderingContext2D.drawImage could not be converted to any of: HTMLImageElement, HTMLCanvasElement, HTMLVideoElement, ImageBitmap. in ctx.drawImage(vid,0,0);
谢谢
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