feat: add retainExif option to retain Exif (#159)

docs/index.html

@@ -153,6 +153,15 @@ <h4 class="card-header">Options</h4>
                   </select>
                 </div>
               </div>
+              <div class="form-group row">
+                <label for="inputRetainExif" class="col-5 col-form-label">retainExif</label>
+                <div class="col-7">
+                  <select class="form-control" name="retainExif" id="inputRetainExif" v-model.number="options.retainExif">
+                    <option :value="false">false</option>
+                    <option :value="true">true</option>
+                  </select>
+                </div>
+              </div>
               <div class="form-group row">
                 <label for="inputMimeType" class="col-5 col-form-label">mimeType</label>
                 <div class="col-7">

docs/js/main.js

@@ -24,6 +24,7 @@ window.addEventListener('DOMContentLoaded', function () {
           height: undefined,
           resize: 'none',
           quality: 0.8,
+          retainExif: false,
           mimeType: '',
           convertTypes: 'image/png',
           convertSize: 5000000,

src/defaults.js

@@ -67,6 +67,12 @@ export default {
    */
   quality: 0.8,
 
+  /**
+   * If set `true`, the compressed image will retain exif.
+   * @type {boolean}
+  */
+  retainExif: false,
+
   /**
    * The mime type of the output image.
    * By default, the original mime type of the source image file will be used.

src/index.js

@@ -13,6 +13,11 @@ import {
   normalizeDecimalNumber,
   parseOrientation,
   resetAndGetOrientation,
+  getEXIF,
+  insertEXIF,
+  base64ToArrayBuffer,
+  blobToBase64,
+  dataURItoBlob,
 } from './utilities';
 
 const { ArrayBuffer, FileReader } = WINDOW;
@@ -37,6 +42,7 @@ export default class Compressor {
       ...DEFAULTS,
       ...options,
     };
+    this.exif = [];
     this.aborted = false;
     this.result = null;
     this.init();
@@ -79,6 +85,9 @@ export default class Compressor {
         const { result } = target;
         const data = {};
 
+        if (options.retainExif) {
+          this.exif = getEXIF(result);
+        }
         if (checkOrientation) {
           // Reset the orientation value to its default value 1
           // as some iOS browsers will render image with its orientation
@@ -279,14 +288,29 @@ export default class Compressor {
     if (this.aborted) {
       return;
     }
-
+    const that = this;
     const done = (result) => {
       if (!this.aborted) {
-        this.done({
-          naturalWidth,
-          naturalHeight,
-          result,
-        });
+        if (options.retainExif && result) {
+          blobToBase64(result, (base64) => {
+            that.done({
+              naturalWidth,
+              naturalHeight,
+              result: dataURItoBlob(
+                arrayBufferToDataURL(
+                  insertEXIF(base64ToArrayBuffer(base64, options.mimeType), that.exif),
+                  options.mimeType,
+                ),
+              ),
+            }, that);
+          });
+        } else {
+          this.done({
+            naturalWidth,
+            naturalHeight,
+            result,
+          });
+        }
       }
     };
 
@@ -301,8 +325,9 @@ export default class Compressor {
     naturalWidth,
     naturalHeight,
     result,
-  }) {
-    const { file, image, options } = this;
+  }, _this = undefined) {
+    const that = _this || this;
+    const { file, image, options } = that;
 
     if (URL && !options.checkOrientation) {
       URL.revokeObjectURL(image.src);

src/utilities.js

@@ -279,3 +279,82 @@ export function getAdjustedSizes(
     height,
   };
 }
+
+export function getEXIF(arrayBuffer) {
+  let head = 0;
+  const segments = [];
+  let length;
+  let endPoint;
+  let seg;
+  const arr = [].slice.call(new Uint8Array(arrayBuffer), 0);
+
+  while (true) {
+    // SOS(Start of Scan)
+    if (arr[head] === 0xff && arr[head + 1] === 0xda) { break; }
+    // SOI(Start of Image)
+    if (arr[head] === 0xff && arr[head + 1] === 0xd8) {
+      head += 2;
+    } else {
+      length = arr[head + 2] * 256 + arr[head + 3];
+      endPoint = head + length + 2;
+      seg = arr.slice(head, endPoint);
+      head = endPoint;
+      segments.push(seg);
+    }
+    if (head > arr.length) {
+      break;
+    }
+  }
+  if (!segments.length) { return []; }
+  let res = [];
+  for (let x = 0; x < segments.length; x += 1) {
+    const s = segments[x];
+    if (s[0] === 0xff && s[1] === 0xe1) {
+      res = res.concat(s);
+    }
+  }
+  return res;
+}
+
+export function insertEXIF(resizedImg, exifArr) {
+  const arr = [].slice.call(new Uint8Array(resizedImg), 0);
+  if (arr[2] !== 0xff || arr[3] !== 0xe0) {
+    return resizedImg;
+  }
+  const app0Length = arr[4] * 256 + arr[5];
+
+  const newImg = [0xff, 0xd8].concat(exifArr, arr.slice(4 + app0Length));
+  return new Uint8Array(newImg);
+}
+
+export function dataURItoBlob(dataURI, mimeType = null) {
+  const mimeString = mimeType || dataURI.split(',')[0].split(':')[1].split(';')[0];
+  const byteString = atob(dataURI.split(',')[1]);
+  const arrayBuffer = new ArrayBuffer(byteString.length);
+  const intArray = new Uint8Array(arrayBuffer);
+
+  for (let i = 0; i < byteString.length; i += 1) {
+    intArray[i] = byteString.charCodeAt(i);
+  }
+  return new Blob([intArray], { type: mimeString });
+}
+
+export function base64ToArrayBuffer(base64) {
+  base64 = base64.replace(/^data:([^;]+);base64,/gim, '');
+  const binary = atob(base64);
+  const len = binary.length;
+  const buffer = new ArrayBuffer(len);
+  const view = new Uint8Array(buffer);
+  for (let i = 0; i < len; i += 1) {
+    view[i] = binary.charCodeAt(i);
+  }
+  return buffer;
+}
+
+export function blobToBase64(blob, callback) {
+  const reader = new FileReader();
+  reader.onloadend = () => {
+    callback(reader.result);
+  };
+  reader.readAsDataURL(blob);
+}

test/specs/Compressor.spec.js

@@ -1,3 +1,5 @@
+import { getEXIF, blobToBase64, base64ToArrayBuffer } from '../../src/utilities';
+
 describe('Compressor', () => {
   it('should be a class (function)', () => {
     expect(Compressor).to.be.a('function');
@@ -81,4 +83,22 @@ describe('Compressor', () => {
       });
     });
   });
+
+  it('should same between the original image`s exif and the compressed image`s exif', (done) => {
+    window.loadImageAsBlob('/base/docs/images/picture.jpg', (image) => {
+      blobToBase64(image, (oBase64) => {
+        const exif = getEXIF(base64ToArrayBuffer(oBase64));
+
+        new Compressor(image, {
+          retainExif: true,
+          success(result) {
+            blobToBase64(result, (cBase64) => {
+              expect(getEXIF(base64ToArrayBuffer(cBase64)).sort()).to.deep.equal(exif.sort());
+              done();
+            });
+          },
+        });
+      });
+    });
+  });
 });

types/index.d.ts

@@ -10,6 +10,7 @@ declare namespace Compressor {
     height?: number;
     resize?: 'contain' | 'cover' | 'none';
     quality?: number;
+    retainExif?: boolean;
     mimeType?: string;
     convertTypes?: string | string[];
     convertSize?: number;