wxservice-web/src/utils/image.js

export function resize(base64, callback) {
  const w = 1440
  let newImage = new Image()
  let quality = 0.8 //压缩系数
  newImage.src = base64
  newImage.setAttribute('crossOrigin', 'Anonymous')
  let imgWidth, imgHeight
  newImage.onload = function () {
    imgWidth = this.width
    imgHeight = this.height
    let canvas = document.createElement('canvas')
    let ctx = canvas.getContext('2d')
    if (Math.max(imgWidth, imgHeight) > w) {
      if (imgWidth > imgHeight) {
        canvas.width = w
        canvas.height = (w * imgHeight) / imgWidth
      } else {
        canvas.height = w
        canvas.width = (w * imgWidth) / imgHeight
      }
    } else {
      canvas.width = imgWidth
      canvas.height = imgHeight
      quality = 0.8
    }
    ctx.clearRect(0, 0, canvas.width, canvas.height)
    ctx.drawImage(this, 0, 0, canvas.width, canvas.height)
    let base64 = canvas.toDataURL('image/jpeg', quality) // 执行压缩
    while (base64.length / 1024 > 500) {
      quality -= 0.01
      base64 = canvas.toDataURL('image/jpeg', quality)
    }
    callback(base64)
  }
}