Add option to keep orientation in metadata.strip() (#50)

Author: educastellano

README.md

@@ -172,9 +172,10 @@ Strip metadata from an image returning a new image buffer.
 await image(path).metadata.strip().save(outPath)
 ```
 
-| Parameter        | Type    | Description                                                         |
-| ---------------- | ------- | ------------------------------------------------------------------- |
-| `opts.keepColor` | boolean | Keep color-transform metadata to avoid color shifts. Default `true` |
+| Parameter              | Type    | Description                                                         |
+| ---------------------- | ------- | ------------------------------------------------------------------- |
+| `opts.keepColor`       | boolean | Keep color-transform metadata to avoid color shifts. Default `true` |
+| `opts.keepOrientation` | boolean | Keep orientation to avoid image rotations. Default `false`          |
 
 Check with `isStripMetadataSupported()` for supported types, only `jpeg` at the moment.
 

package.json

@@ -31,15 +31,15 @@
   "homepage": "https://github.com/holepunchto/bare-media#readme",
   "dependencies": {
     "bare-bmp": "^1.0.0",
-    "bare-exif": "^1.0.0",
+    "bare-exif": "^1.1.0",
     "bare-fetch": "^3.0.1",
     "bare-ffmpeg": "^1.2.1",
     "bare-fs": "^4.1.5",
     "bare-gif": "^1.1.2",
     "bare-heif": "^1.0.5",
     "bare-ico": "^1.0.0",
     "bare-image-resample": "^1.0.1",
-    "bare-jpeg": "^1.1.0",
+    "bare-jpeg": "^1.1.1",
     "bare-png": "^1.0.2",
     "bare-svg": "^1.0.1",
     "bare-tiff": "^1.0.1",

src/image/metadata.js

@@ -74,14 +74,40 @@ async function metadata(buffer, opts = {}) {
 }
 
 async function stripJPEG(buffer, opts = {}) {
-  const { keepColor = true } = opts
+  const { keepColor = true, keepOrientation = false } = opts
 
   const jpeg = await import('bare-jpeg')
+  const APP1 = 0xe1
   const APP14 = 0xee
+
   const { markers } = jpeg.readHeader(buffer)
-  const keep = keepColor ? markers.filter((m) => m.marker === APP14) : []
 
-  return jpeg.replaceMarkers(buffer, keep)
+  let newMarkers = []
+
+  if (keepColor) {
+    newMarkers = markers.filter((m) => m.marker === APP14)
+  }
+
+  if (keepOrientation) {
+    const exif = await import('bare-exif')
+    const tags = exif.constants.tags
+    const data = new exif.Data(buffer)
+
+    for (const tag of Object.values(tags)) {
+      if (tag !== tags.ORIENTATION) {
+        data.removeEntry(tag)
+      }
+    }
+
+    const rawExif = data.saveData()
+
+    newMarkers.push({
+      marker: APP1,
+      data: rawExif
+    })
+  }
+
+  return jpeg.replaceMarkers(buffer, newMarkers)
 }
 
 async function strip(buffer, opts = {}) {

test/fixtures/exif.jpg

@@ -86,6 +86,8 @@ test('image.metadata.strip() strips all metadata', async (t) => {
 
   {
     const metadata = await image(newImage).metadata()
+
+    // no exif data is stored
     t.absent(metadata.exif.COLOR_SPACE)
     t.absent(metadata.exif.EXIF_VERSION)
     t.absent(metadata.exif.FLASH_PIX_VERSION)
@@ -95,6 +97,39 @@ test('image.metadata.strip() strips all metadata', async (t) => {
   }
 })
 
+test('image.metadata.strip() strips all metadata, except orientation', async (t) => {
+  const path = './test/fixtures/exif.jpg'
+
+  const metadata = await image(path).metadata()
+
+  t.ok(metadata.exif.COLOR_SPACE)
+  t.ok(metadata.exif.EXIF_VERSION)
+  t.ok(metadata.exif.FLASH_PIX_VERSION)
+  t.ok(metadata.exif.RESOLUTION_UNIT)
+  t.ok(metadata.exif.MAKE)
+  t.ok(metadata.exif.LENS_MAKE)
+  t.ok(metadata.exif.ARTIST)
+  t.ok(metadata.exif.ORIENTATION)
+  t.is(metadata.orientation, 6)
+
+  const newImage = await image(path).metadata.strip({ keepOrientation: true })
+
+  {
+    const metadata = await image(newImage).metadata()
+
+    // some mandatory tags remain as for the spec
+    t.ok(metadata.exif.COLOR_SPACE)
+    t.ok(metadata.exif.EXIF_VERSION)
+    t.ok(metadata.exif.FLASH_PIX_VERSION)
+    t.ok(metadata.exif.RESOLUTION_UNIT)
+    t.absent(metadata.exif.MAKE)
+    t.absent(metadata.exif.LENS_MAKE)
+    t.absent(metadata.exif.ARTIST)
+    t.ok(metadata.exif.ORIENTATION)
+    t.is(metadata.orientation, 6)
+  }
+})
+
 test('image.metadata.strip().save() strips all metadata and saves the file', async (t) => {
   const path = './test/fixtures/exif-orientation.jpg'
   const outPath = barePath.join(os.tmpdir(), randomFileName('jpg'))