vue+vant图片压缩后上传

vue+vant图片压缩后上传

vue文件写入

在utils文件夹下的index中写入 图片压缩代码

/**
 * @description: 图片压缩
 * @param {*} img
 * @return {*}
 */
export const compressImg = (img) => {
  let canvas = document.createElement('canvas')
  let ctx = canvas.getContext('2d')
  let tCanvas = document.createElement('canvas')
  let tctx = tCanvas.getContext('2d')
  let width = img.width
  let height = img.height
  //如果图片大于四百万像素，计算压缩比并将大小压至400万以下
  let ratio
  if ((ratio = (width * height) / 4000000) > 1) {
    console.log('大于400万像素')
    ratio = Math.sqrt(ratio)
    width /= ratio
    height /= ratio
  } else {
    ratio = 1
  }
  canvas.width = width
  canvas.height = height
  //    铺底色
  ctx.fillStyle = '#fff'
  ctx.fillRect(0, 0, canvas.width, canvas.height)
  //如果图片像素大于100万则使用瓦片绘制
  let count
  if ((count = (width * height) / 1000000) > 1) {
    console.log('超过100W像素')
    count = ~~(Math.sqrt(count) + 1) //计算要分成多少块瓦片
    // 计算每块瓦片的宽和高
    let nw = ~~(width / count)
    let nh = ~~(height / count)
    tCanvas.width = nw
    tCanvas.height = nh
    for (let i = 0; i < count; i++) {
      for (let j = 0; j < count; j++) {
        tctx.drawImage(
          img,
          i * nw * ratio,
          j * nh * ratio,
          nw * ratio,
          nh * ratio,
          0,
          0,
          nw,
          nh
        )
        ctx.drawImage(tCanvas, i * nw, j * nh, nw, nh)
      }
    }
  } else {
    ctx.drawImage(img, 0, 0, width, height)
  }
  //进行最小压缩
  let minData = canvas.toDataURL('image/jpeg', 0.1)
  tCanvas.width = tCanvas.height = canvas.width = canvas.height = 0
  return minData
}