尝试使用Canvas和DrawImage以90度显示低速率视频

本文介绍了尝试使用Canvas和DrawImage以90度显示低速率视频的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我想以2帧/秒的速度显示旋转的相机视频。以下代码显示以90度旋转的240 x 320图像。除非刷新浏览器，否则图像不会更新。正在改变的源是cam_1.jpg。看来，一旦DrawImage有一个src图像，它会寻找更新。

I would like to display rotated camera video at a rate of 2 frames/second. The following code displays a 240 x 320 image rotated at 90 degrees. The image does not update unless I refresh the browser. The source that is changing is cam_1.jpg. It seems that once DrawImage has a src image, it does look for an update.

我还没有学到什么？感谢您的时间和专业知识。

What have I not learned yet? Thank You for your time and expertise.

<title>CamDisplay</title></head><body>
<canvas height="320" width="240"></canvas>
<script type="text/javascript" charset="utf-8">
    var cam = new Image;
    window.onload = function(){
        var c = document.getElementsByTagName('canvas')[0];
        var ctx = c.getContext('2d');
        setInterval(function(){
            ctx.save();
            ctx.clearRect( 0, 0, 240, 320 );
            ctx.translate( 240, 0);

            cam.src = 'cam_1.jpg?uniq='+Math.random();

            ctx.rotate( 1.57);
            ctx.drawImage( cam, 0, 0 );
                            ctx.restore();
        },500);
    };
</script>
</body>
</html>

推荐答案

图片无法加载。 try

the image is not getting time to load. try

var cam = new Image;
var c = document.getElementsByTagName('canvas')[0];
var ctx = c.getContext('2d');

cam.onload = function() {
        ctx.save();
         ctx.clearRect( 0, 0, 240, 320 );
         ctx.translate( 240, 0);
         ctx.rotate( 1.57);
         ctx.drawImage( this, 0, 0 );
        ctx.restore();  
    }

window.onload = function(){
    setInterval(function(){
        cam.src = 'cam_1.jpg?uniq='+Math.random();
    },500);
}

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