仅捕获检测到的人脸正方形 JS

Question

我正在通过网络摄像头中的 JS 运行人脸检测 model，它可以识别人脸并正确绘制框。 然后，我如何才能将检测到的面部仅作为图像保存到我的计算机本地？

我很感激任何帮助！ 我卡住了！

代码（来自 face-api.js）如下：

JavaScript

const video = document.getElementById('video')
const snap = document.getElementById('snap')
const canvas = document.getElementById('canvas')



Promise.all([
  faceapi.nets.tinyFaceDetector.loadFromUri('/static/models'),
  faceapi.nets.faceExpressionNet.loadFromUri('/static/models')
]).then(startVideo)

function startVideo() {
  navigator.getUserMedia(
    { video: {} },
    stream => video.srcObject = stream,
    err => console.error(err)
  )
}



video.addEventListener('play', () => {
  const canvas = faceapi.createCanvasFromMedia(video)
  document.body.append(canvas)
  const displaySize = { width: video.width, height: video.height }
  faceapi.matchDimensions(canvas, displaySize)
  setInterval(async () => {
    const detections = await faceapi.detectAllFaces(video, new faceapi.TinyFaceDetectorOptions()).withFaceExpressions()
    const resizedDetections = faceapi.resizeResults(detections, displaySize)
    canvas.getContext('2d').clearRect(0, 0, canvas.width, canvas.height)
    faceapi.draw.drawDetections(canvas, resizedDetections)
    faceapi.draw.drawFaceExpressions(canvas, resizedDetections)
  }, 100)
})

HTML

<div id="cam">
    <video id="video" width="720" height="560" autoplay muted></video>
</div>
<div class="control">
    <button id="snap" class="btn btn-primary">Capture</button>
</div>
<canvas id="canvas" width="197" height="197"></canvas>

Answer 1

你有一个 canvas。 您可以保存 canvas： 如何使用 canvas.toDataURL() 将 Canvas 保存为图像？

假设detections是一个数组：

// Taken from https://stackoverflow.com/a/15685544/4088472
function saveCanvas(canvas) {
  const image = canvas.toDataURL("image/png").replace("image/png", "image/octet-stream");  
  window.location.href=image; // it will save locally
}


// ... in your code ...
canvas.getContext('2d').clearRect(0, 0, canvas.width, canvas.height)
faceapi.draw.drawDetections(canvas, resizedDetections)
faceapi.draw.drawFaceExpressions(canvas, resizedDetections)
if (detections.length)
   saveCanvas(canvas);