图片压缩，ios使用uni，安卓使用canvas压缩

const compressImage = (index, tempImageArr,callback,newArr=[])=> {

  let temp = tempImageArr[index]; 
  if (index < tempImageArr.length) {
    uni.getImageInfo({
      src: tempImageArr[index],
      success: info => {
        let ratio = 0.8; //压缩比例
        let quality =  0.8;  //图片质量
        let canvasWidth = info.width;
        let canvasHeight = info.height;
        while (canvasWidth > 2000 || canvasHeight > 2000) {
          //比例取整
          canvasWidth = Math.trunc(info.width / ratio)
          canvasHeight = Math.trunc(info.height / ratio)
          ratio += 0.1;
        }

        if(/IOS|ios|Ios/.test(systemInfo.platform)) {
          uni.compressImage({
            quality: quality,
            src: temp,
            success: res => {
              newArr.push({ compress: res.tempFilePath, temp});
              compressImage(++index, tempImageArr, callback, newArr);
            },
            fail:e => {
            }
          })
        } else {
          uni.createSelectorQuery().selectAll('#canvas').node(res => {
            const canvas = res[0].node;
            canvas.width = canvasWidth;
            canvas.height = canvasHeight;
            const ctx = canvas.getContext('2d');
            const image = canvas.createImage();
            image.src = tempImageArr[index];
            image.onload = () => {
              ctx.drawImage(image, 0, 0, canvasWidth, canvasHeight);
              uni.canvasToTempFilePath({
                canvas: canvas,
                fileType: 'jpg',
                quality: quality,
                success: image => {
                  newArr.push({ compress: image.tempFilePath, temp}); 
                  compressImage(++index, tempImageArr, callback, newArr);
                },
                fail: err => {
                  console.log(err)
                }
              })
            }
          }).exec()
        }
      },
      fail: e => {}
    })
  } else {
    callback(newArr)
  }

  
  }