重新加载时 canvas 以 0 宽度和 0 高度开始

Question

我是 bable js 的初学者。我发现问题出在 babel js 中。但是不知道怎么改。我在 babel js 中尝试新事物。请帮我。我希望动画以完整的 window 高度和宽度开始。提前致谢。 canvas 最初以 height="0", width="0" 开头。这就是为什么当我重新加载时我看不到动画。如果我调整 window 的大小，则会显示动画。代码如下：

**HTML**

<div class="crowd">
      <canvas id="crowd-simulator"></canvas>
    </div>

**CSS**

.crowd{
    height: 100%;
    z-index: -999;
}
#crowd-simulator {
    width: 100vw;
    height: 100vh;
    position: absolute;
    z-index: -999;
  }

**Babel Js**

    const config = {
      src: 'https://s3-us-west-2.amazonaws.com/s.cdpn.io/175711/open-peeps-sheet.png',
      rows: 15,
      cols: 7
    }

    // UTILS

    const randomRange = (min, max) => min + Math.random() * (max - min)

    const randomIndex = (array) => randomRange(0, array.length) | 0

    const removeFromArray = (array, i) => array.splice(i, 1)[0]

    const removeItemFromArray = (array, item) => removeFromArray(array, array.indexOf(item))

    const removeRandomFromArray = (array) => removeFromArray(array, randomIndex(array))

    const getRandomFromArray = (array) => (
      array[randomIndex(array) | 0]
    )

    // TWEEN FACTORIES

    const resetPeep = ({ stage, peep }) => {
      const direction = Math.random() > 0.5 ? 1 : -1
      // using an ease function to skew random to lower values to help hide that peeps have no legs
      const offsetY = 100 - 250 * gsap.parseEase('power2.in')(Math.random())
      const startY = stage.height - peep.height + offsetY
      let startX
      let endX

      if (direction === 1) {
        startX = -peep.width
        endX = stage.width
        peep.scaleX = 1
      } else {
        startX = stage.width + peep.width
        endX = 0
        peep.scaleX = -1
      }

      peep.x = startX
      peep.y = startY
      peep.anchorY = startY

      return {
        startX,
        startY,
        endX
      }
    }

    const normalWalk = ({ peep, props }) => {
      const {
        startX,
        startY,
        endX
      } = props

      const xDuration = 10
      const yDuration = 0.25

      const tl = gsap.timeline()
      tl.timeScale(randomRange(0.5, 1.5))
      tl.to(peep, {
        duration: xDuration,
        x: endX,
        ease: 'none'
      }, 0)
      tl.to(peep, {
        duration: yDuration,
        repeat: xDuration / yDuration,
        yoyo: true,
        y: startY - 10
      }, 0)

      return tl
    }

    const walks = [
      normalWalk,
    ]

    // CLASSES

    class Peep {
      constructor({
        image,
        rect,
      }) {
        this.image = image
        this.setRect(rect)

        this.x = 0
        this.y = 0
        this.anchorY = 0
        this.scaleX = 1
        this.walk = null
      }

      setRect(rect) {
        this.rect = rect
        this.width = rect[2]
        this.height = rect[3]

        this.drawArgs = [
          this.image,
          ...rect,
          0, 0, this.width, this.height
        ]
      }

      render(ctx) {
        ctx.save()
        ctx.translate(this.x, this.y)
        ctx.scale(this.scaleX, 1)
        ctx.drawImage(...this.drawArgs)
        ctx.restore()
      }
    }

    // MAIN

    const img = document.createElement('img')
    img.onload = init
    img.src = config.src

    const canvas = document.querySelector('#crowd-simulator')
    const ctx = canvas.getContext('2d')

    const stage = {
      width: 0,
      height: 0,
    }

    const allPeeps = []
    const availablePeeps = []
    const crowd = []

    function init() {
      createPeeps()

      // resize also (re)populates the stage
      resize()

      gsap.ticker.add(render)
      window.addEventListener('resize', resize)
    }

    function createPeeps() {
      const {
        rows,
        cols
      } = config
      const {
        naturalWidth: width,
        naturalHeight: height
      } = img
      const total = rows * cols
      const rectWidth = width / rows
      const rectHeight = height / cols

      for (let i = 0; i < total; i++) {
        allPeeps.push(new Peep({
          image: img,
          rect: [
            (i % rows) * rectWidth,
            (i / rows | 0) * rectHeight,
            rectWidth,
            rectHeight,
          ]
        }))
      }
    }

    function resize() {
      stage.width = canvas.clientWidth
      stage.height = canvas.clientHeight
      canvas.width = stage.width * devicePixelRatio
      canvas.height = stage.height * devicePixelRatio

      crowd.forEach((peep) => {
        peep.walk.kill()
      })

      crowd.length = 0
      availablePeeps.length = 0
      availablePeeps.push(...allPeeps)

      initCrowd()
    }

    function initCrowd() {
      while (availablePeeps.length) {
        // setting random tween progress spreads the peeps out
        addPeepToCrowd().walk.progress(Math.random())
      }
    }

    function addPeepToCrowd() {
      const peep = removeRandomFromArray(availablePeeps)
      const walk = getRandomFromArray(walks)({
        peep,
        props: resetPeep({
          peep,
          stage,
        })
      }).eventCallback('onComplete', () => {
        removePeepFromCrowd(peep)
        addPeepToCrowd()
      })

      peep.walk = walk

      crowd.push(peep)
      crowd.sort((a, b) => a.anchorY - b.anchorY)

      return peep
    }

    function removePeepFromCrowd(peep) {
      removeItemFromArray(crowd, peep)
      availablePeeps.push(peep)
    }

    function render() {
      canvas.width = canvas.width
      ctx.save()
      ctx.scale(devicePixelRatio, devicePixelRatio)

      crowd.forEach((peep) => {
        peep.render(ctx)
      })

      ctx.restore()
    }

Answer 1

您似乎只是在调整大小时使用正确的尺寸填充舞台：

    function resize() {
      stage.width = canvas.clientWidth
      stage.height = canvas.clientHeight
}

尝试将舞台设置为一些初始尺寸。目前是：

 const stage = {
      width: 0,
      height: 0,
    }

所以试试这个：

 const stage = {
      width: canvas.clientWidth,
      height: canvas.clientHeight
    }

重新加载时 canvas 以 0 宽度和 0 高度开始

At reload canvas starts with 0 width & 0 height

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