初始化项目

src/utils/image.js

@@ -0,0 +1,92 @@
+export default class ImageCompress {
+  constructor(file, fileSize, maxWH = 1920) {
+    this.file = file
+    this.fileSize = fileSize
+    this.maxWH = maxWH // 最大长宽
+  }
+
+  compress() {
+    // 压缩
+    const fileType = this.file.type
+    const fileSize = this.file.size / 1024
+    return new Promise(resolve => {
+      const reader = new FileReader()
+      reader.readAsDataURL(this.file)
+      reader.onload = () => {
+        const canvas = document.createElement('canvas')
+        const img = document.createElement('img')
+        img.src = reader.result
+        img.onload = () => {
+          const ctx = canvas.getContext('2d')
+          const _dWH = this.dWH(img.width, img.height, this.maxWH)
+          canvas.width = _dWH.width
+          canvas.height = _dWH.height
+
+          // 清空后, 重写画布
+          ctx.clearRect(0, 0, canvas.width, canvas.height)
+          ctx.drawImage(img, 0, 0, canvas.width, canvas.height)
+
+          const newImgData = canvas.toDataURL(fileType, 0.90)
+
+          // 压缩宽高后的图像大小
+          const newImgSize = this.fileSizeKB(newImgData)
+
+          if (newImgSize > this.fileSize) {
+            console.log('图片尺寸太大!' + fileSize + ' >> ' + newImgSize)
+          }
+
+          const blob = this.dataURLtoBlob(newImgData, fileType)
+          const nfile = new File([blob], this.file.name)
+          resolve(nfile)
+        }
+      }
+    })
+  }
+
+  /**
+   * 长宽等比缩小
+   * 图像的一边(长或宽)为最大目标值
+   */
+  dWH(srcW, srcH, dMax) {
+    const defaults = {
+      width: srcW,
+      height: srcH
+    }
+    if (Math.max(srcW, srcH) > dMax) {
+      if (srcW > srcH) {
+        defaults.width = dMax
+        defaults.height = Math.round(srcH * (dMax / srcW))
+        return defaults
+      } else {
+        defaults.height = dMax
+        defaults.width = Math.round(srcW * (dMax / srcH))
+        return defaults
+      }
+    } else {
+      return defaults
+    }
+  }
+
+  fileSizeKB(dataURL) {
+    let sizeKB = 0
+    sizeKB = Math.round((dataURL.split(',')[1].length * 3 / 4) / 1024)
+    return sizeKB
+  }
+
+  /**
+   * 转为Blob
+   */
+  dataURLtoBlob(dataURL, fileType) {
+    const byteString = atob(dataURL.split(',')[1])
+    let mimeString = dataURL.split(',')[0].split(':')[1].split(';')[0]
+    const ab = new ArrayBuffer(byteString.length)
+    const ia = new Uint8Array(ab)
+    for (let i = 0; i < byteString.length; i++) {
+      ia[i] = byteString.charCodeAt(i)
+    }
+    if (fileType) {
+      mimeString = fileType
+    }
+    return new Blob([ab], { type: mimeString, lastModifiedDate: new Date() })
+  }
+}