（Javascript）AI数字人mp4转canvas播放并去除背景绿幕

1、需求介绍

H5页面嵌入AI数字人播报，但生成的数字人是mp4格式且有绿幕背景，需要转成canvas并去除背景；

2、效果：

去除前：

去除后：

3、代码

<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
  <style>
    * {
      margin: 0;
      padding: 0;
    }
  </style>
</head>

<body>
  <button onclick="playOrPause()">播放/暂停</button>
  <button onclick="muted()">静音</button>
  <div style="height: 400px; width:300px; ">
    <video id="video" controls style="width: 100%; height: 100%; object-fit: contain" autoplay webkit-playsinline="true"
      src='123.mp4'></video>
  </div>
  <script>
    var VideoToCanvas = (function (window, document) {
      function VideoToCanvas(videoElement) {
        if (!videoElement) { return; }
        var canvas = document.createElement('canvas');
        canvas.width = videoElement.offsetWidth;
        canvas.height = videoElement.offsetHeight;
        ctx = canvas.getContext('2d');

        var newVideo = videoElement.cloneNode(false);

        newVideo.addEventListener('play', function () {
          computeFrame();
        }, false);


        function computeFrame() {
          if (newVideo.paused || newVideo.ende) {
            return;
          }
          ctx.drawImage(newVideo, 0, 0, canvas.width, canvas.height);
          // 获取到绘制的canvas的所有像素rgba值组成的数组
          let frame = ctx.getImageData(0, 0, canvas.width, canvas.height);

          // 共有多少像素点
          const pointLens = frame.data.length / 4;
          for (let i = 0; i < pointLens; i++) {
            let r = frame.data[i * 4];
            let g = frame.data[i * 4 + 1];
            let b = frame.data[i * 4 + 2];

            // 判断如果rgb值在这个范围内则是绿幕背景，设置alpha值为0 
            // 同理不同颜色的背景调整rgb的判断范围即可
            if (r < 100 && g > 120 && b < 200) {
              frame.data[i * 4 + 3] = 0;
            }
          }
          // 重新绘制到canvas中显示
          ctx.putImageData(frame, 0, 0);
          // 递归调用
          setTimeout(computeFrame, 0);
        }

        videoElement.parentNode.replaceChild(canvas, video);

        this.play = function () {
          newVideo.play();
        };

        this.pause = function () {
          newVideo.pause();
        };

        this.playPause = function () {
          if (newVideo.paused) {
            this.play();
          } else {
            this.pause();
          }
        };
        this.muted = function () {
          newVideo.muted = !newVideo.muted;
        }
        this.change = function (src) {
          if (!src) { return; }
          newVideo.src = src;
          computeFrame();
        };
      }
      return VideoToCanvas;
    })(window, document);

    var video = document.getElementById('video');
    var videoCanvas = new VideoToCanvas(video);
    
    function playOrPause() {
      videoCanvas.playPause();
    }
    function muted() {
      videoCanvas.muted();
    }
  </script>