Test: add set orientation

src/index.test.ts

@@ -1,7 +1,12 @@
 import * as fs from 'fs';
-import { getOrientation } from './index';
+import { getOrientation, OrientationCode, updateOrientationCode } from './index';
 
 describe('imageUtil', () => {
+  const readFile = (name: string) => {
+    const buffer = fs.readFileSync(`test/${name}`);
+    return buffer.buffer;
+  };
+
   describe('getOrientation()', () => {
     it('accepts Buffer', async () => {
       const buffer = fs.readFileSync(`test/000-1.jpg`);
@@ -23,11 +28,6 @@ describe('imageUtil', () => {
     });
 
     describe('recognize orientation from file of', () => {
-      const readFile = (name: string) => {
-        const buffer = fs.readFileSync(`test/${name}`);
-        return buffer.buffer;
-      };
-
       it('original image', async () => {
         const arr = readFile('000-1.jpg');
         const orientation = await getOrientation(arr);
@@ -95,4 +95,68 @@ describe('imageUtil', () => {
       });
     });
   });
+
+  describe('updateOrientationCode()', () => {
+    it('accepts Buffer', async () => {
+      const buffer = fs.readFileSync('test/000-flipped-2.jpg');
+      await updateOrientationCode(buffer.buffer, OrientationCode.original);
+      const orientation = await getOrientation(buffer.buffer);
+      expect(orientation).toEqual({ rotation: 0, flipped: false });
+    });
+
+    it('accepts ArrayBuffer', async () => {
+      const buffer = fs.readFileSync('test/000-flipped-2.jpg');
+      const arrayBuffer = new ArrayBuffer(buffer.byteLength);
+      const view = new DataView(arrayBuffer);
+      buffer.forEach((value, index) => {
+        view.setUint8(index, value);
+      });
+      await updateOrientationCode(arrayBuffer, OrientationCode.original);
+
+      const orientation = await getOrientation(arrayBuffer);
+      expect(orientation).toEqual({ rotation: 0, flipped: false });
+    });
+
+    describe('update orientation from file of', () => {
+      it('flipped image update orientation', async () => {
+        const arr = readFile('000-flipped-2.jpg');
+        await updateOrientationCode(arr, OrientationCode.original);
+        const orientation = await getOrientation(arr);
+        expect(orientation).toEqual({ rotation: 0, flipped: false });
+      });
+
+      it('image without Exif', async () => {
+        const arr = readFile('no-exif.jpg');
+        const errorMessage = 'The File you are trying to update has no exif data';
+
+        try {
+          await updateOrientationCode(arr, OrientationCode.original);
+        } catch (error) {
+          expect(error.message).toBe(errorMessage);
+        }
+      });
+
+      it('non-JPEG image', async () => {
+        const arr = readFile('png.png');
+        const errorMessage = 'The File you are trying to update is not a jpeg';
+
+        try {
+          await updateOrientationCode(arr, OrientationCode.original);
+        } catch (error) {
+          expect(error.message).toBe(errorMessage);
+        }
+      });
+
+      it('empty file', async () => {
+        const arr = readFile('empty.txt');
+        const errorMessage = 'The File you are trying to update is not a jpeg';
+
+        try {
+          await updateOrientationCode(arr, OrientationCode.original);
+        } catch (error) {
+          expect(error.message).toBe(errorMessage);
+        }
+      });
+    });
+  });
 });

src/index.ts

@@ -92,17 +92,8 @@ export async function readOrientationCode (
     return OrientationCode.unknown;
   }
 
-  const tiffHeaderOffset =
-    segmentOffset + statics.offsets.tiffHeader.fromSegment;
-  const littleEndian = isLittleEndian(view, tiffHeaderOffset);
-  const ifdPosition = findIfdPosition(view, tiffHeaderOffset, littleEndian);
-  const ifdFieldOffset = ifdPosition + statics.ifdFieldCountLength;
+  const {littleEndian, orientationOffset} = getOrientationOffsetAndLittleEndian(view, segmentOffset);
 
-  const orientationOffset = findOrientationOffset(
-    view,
-    ifdFieldOffset,
-    littleEndian,
-  );
   if (orientationOffset < 0) {
     console.warn('Rotation information was not found');
     return OrientationCode.unknown;
@@ -116,6 +107,42 @@ export async function readOrientationCode (
   return orientation;
 }
 
+export async function updateOrientationCode (
+  input: File | Buffer | ArrayBuffer,
+  orientation: OrientationCode,
+): Promise<void> {
+  const view = await prepareDataView(input);
+  if (!isValidJpeg(view)) {
+    throw new Error('The File you are trying to update is not a jpeg');
+  }
+
+  const segmentOffset = await findExifSegmentOffset(view);
+  if (segmentOffset < 0) {
+    throw new Error('The File you are trying to update has no exif data');
+  }
+
+  const {littleEndian, orientationOffset} = getOrientationOffsetAndLittleEndian(view, segmentOffset);
+  setOrientationValueAt(
+    view,
+    orientationOffset,
+    orientation,
+    littleEndian,
+  );
+}
+
+function getOrientationOffsetAndLittleEndian (view: DataView, segmentOffset: number) {
+  const tiffHeaderOffset = segmentOffset + statics.offsets.tiffHeader.fromSegment;
+  const littleEndian = isLittleEndian(view, tiffHeaderOffset);
+  const ifdPosition = findIfdPosition(view, tiffHeaderOffset, littleEndian);
+  const ifdFieldOffset = ifdPosition + statics.ifdFieldCountLength;
+  const orientationOffset = findOrientationOffset(
+    view,
+    ifdFieldOffset,
+    littleEndian,
+  );
+  return {littleEndian, orientationOffset};
+}
+
 async function prepareDataView (
   input: File | Buffer | ArrayBuffer,
 ): Promise<DataView> {
@@ -300,6 +327,15 @@ function readOrientationValueAt (
   return orientation;
 }
 
+function setOrientationValueAt (
+  view: DataView,
+  offset: number,
+  orientation: OrientationCode,
+  littleEndian: boolean,
+) {
+  view.setUint16(offset, orientation, littleEndian);
+}
+
 /**
  * Converts orientation code specified in Exif to readable information.
  * @param input JPEG file data.