const container = pdfContainer.value const canvas = pdfCanvas.value const mouseX = events.clientX - container.offsetLeft const mouseY = events.clientY - container.offsetTop const zoomDelta = events.deltaY * -0.01 const zoom = canvas.width / (canvas.width * (1 + zoomDelta)) const offsetX = mouseX - mouseX * zoom const offsetY = mouseY - mouseY * zoom canvas.style.transformOrigin = `${mouseX}px ${mouseY}px` canvas.style.transform = `scale(${zoom})`

根据你提供的更新后的代码，我注意到你使用了`pdfContainer.value`和`pdfCanvas.value`来获取`container`和`canvas`的引用。这样做是为了使用Vue的ref属性来获取DOM元素的引用。

然而，你可能需要确保在使用这些引用之前，确保它们已经成功地被赋值。如果在此之前没有给`pdfContainer`和`pdfCanvas`赋值，这样的错误就会发生。请确保在使用这些值之前，它们已经被正确地赋值。

另外，请确保你在代码中正确地引入了相关的库或框架，并且这些库或框架已经正确地初始化。

如果问题仍然存在，请提供更多关于错误的上下文信息，以便我可以更好地帮助你解决问题。

相关问题

handleWheel(event) { event.preventDefault() const container = this.$refs.pdfContainer const canvas = this.$refs.pdfCanvas const mouseX = event.clientX - container.offsetLeft const mouseY = event.clientY - container.offsetTop const zoomDelta = event.deltaY * -0.01 const zoom = canvas.width / (canvas.width * (1 + zoomDelta)) const offsetX = mouseX - mouseX * zoom const offsetY = mouseY - mouseY * zoom canvas.style.transformOrigin = `${mouseX}px ${mouseY}px` canvas.style.transform = `scale(${zoom})` canvas.style.marginLeft = `${offsetX}px` canvas.style.marginTop = `${offsetY}px` } 这样使用文件没有被放大，被挤出了画面

涌现。通过深入学习和理解这些研究成果，我们能够更好地应用机器学根据你提供的代码，我看到你正在处理滚轮事件（`handleWheel`函数），并尝试对`canvas`元素进行放大和平移操作以实现缩放效果。你的代码中使用了`transform`属性习技术解决实际问题，并推动人工智能的发展。

希望以上简报对您有所帮助！如需获取更多相关信息，请继续深入查阅相关文献。

用canvas绘制一个可拖拽的多边形

抱歉，我作为AI语言模型无法提供图形化界面，但我可以给你提供绘制多边形的代码，您可以在您的项目中使用它：

<canvas id="myCanvas" width="500" height="500"></canvas>

const canvas = document.getElementById('myCanvas');
const ctx = canvas.getContext('2d');

let isDragging = false;
let dragIndex = -1;
let mouseX = 0;
let mouseY = 0;

const polygon = {
  points: [
    { x: 100, y: 100 },
    { x: 200, y: 100 },
    { x: 200, y: 200 },
    { x: 100, y: 200 }
  ],
  strokeColor: '#000',
  fillColor: '#f00'
};

function drawPolygon() {
  ctx.beginPath();
  ctx.moveTo(polygon.points[0].x, polygon.points[0].y);
  for (let i = 1; i < polygon.points.length; i++) {
    ctx.lineTo(polygon.points[i].x, polygon.points[i].y);
  }
  ctx.closePath();
  ctx.strokeStyle = polygon.strokeColor;
  ctx.stroke();
  ctx.fillStyle = polygon.fillColor;
  ctx.fill();
}

function isInsidePolygon() {
  let inside = false;
  for (let i = 0, j = polygon.points.length - 1; i < polygon.points.length; j = i++) {
    const xi = polygon.points[i].x;
    const yi = polygon.points[i].y;
    const xj = polygon.points[j].x;
    const yj = polygon.points[j].y;

    const intersect = ((yi > mouseY) !== (yj > mouseY)) &&
      (mouseX < (xj - xi) * (mouseY - yi) / (yj - yi) + xi);

    if (intersect) inside = !inside;
  }

  return inside;
}

function onMouseDown(event) {
  mouseX = event.clientX - canvas.offsetLeft;
  mouseY = event.clientY - canvas.offsetTop;

  for (let i = 0; i < polygon.points.length; i++) {
    const point = polygon.points[i];
    const distance = Math.sqrt((point.x - mouseX) ** 2 + (point.y - mouseY) ** 2);

    if (distance < 10) {
      isDragging = true;
      dragIndex = i;
      break;
    }
  }
}

function onMouseMove(event) {
  if (isDragging) {
    mouseX = event.clientX - canvas.offsetLeft;
    mouseY = event.clientY - canvas.offsetTop;

    polygon.points[dragIndex].x = mouseX;
    polygon.points[dragIndex].y = mouseY;

    ctx.clearRect(0, 0, canvas.width, canvas.height);
    drawPolygon();
  }
}

function onMouseUp(event) {
  isDragging = false;
  dragIndex = -1;
}

canvas.addEventListener('mousedown', onMouseDown);
canvas.addEventListener('mousemove', onMouseMove);
canvas.addEventListener('mouseup', onMouseUp);

drawPolygon();

这是一个绘制一个四边形的多边形的代码，并且可以拖动顶点。您可以通过修改 `polygon.points` 数组来绘制不同形状的多边形。