Use the built-in jpg.js decoder for JPEG images with non-default EXIF orientation (bug 1942064)

[Snuffleupagus]

The new EXIF parsing, during JpegImage.canUseImageDecoder, takes well below 1 ms in my testing which should be fast enough to not be an issue.

The EXIF parsing is done using https://github.com/exif-js/exif-js/, which is released under the MIT License. Note that while it's available on NPM we're however not using that since:

• The package is not fully up-to-date, given the latest changes in the Git repository.
• We only need a subset of the functionality, and this way we're able to simplify and shorten the code.
• Given the age of that project the code isn't directly compatible with JavaScript modules.

[Snuffleupagus]

/botio unittest

[moz-tools-bot]

From: Bot.io (Linux m4)

---

Received

Command cmd_unittest from @Snuffleupagus received. Current queue size: 0

Live output at: http://54.241.84.105:8877/3dbc03217247b4a/output.txt

[moz-tools-bot]

From: Bot.io (Windows)

---

Received

Command cmd_unittest from @Snuffleupagus received. Current queue size: 1

Live output at: http://54.193.163.58:8877/66c431f69767b4e/output.txt

[moz-tools-bot]

From: Bot.io (Linux m4)

---

Success

Full output at http://54.241.84.105:8877/3dbc03217247b4a/output.txt

Total script time: 2.33 mins

• Unit Tests: Passed

[moz-tools-bot]

From: Bot.io (Windows)

---

Failed

Full output at http://54.193.163.58:8877/66c431f69767b4e/output.txt

Total script time: 8.16 mins

• Unit Tests: FAILED

[Snuffleupagus]

/botio browsertest

[moz-tools-bot]

From: Bot.io (Linux m4)

---

Received

Command cmd_browsertest from @Snuffleupagus received. Current queue size: 1

Live output at: http://54.241.84.105:8877/a619053271dc48e/output.txt

[moz-tools-bot]

From: Bot.io (Windows)

---

Received

Command cmd_browsertest from @Snuffleupagus received. Current queue size: 1

Live output at: http://54.193.163.58:8877/9a2074e01a17677/output.txt

[moz-tools-bot]

From: Bot.io (Linux m4)

---

Success

Full output at http://54.241.84.105:8877/a619053271dc48e/output.txt

Total script time: 16.55 mins

• Regression tests: Passed

[moz-tools-bot]

From: Bot.io (Windows)

---

Success

Full output at http://54.193.163.58:8877/9a2074e01a17677/output.txt

Total script time: 30.12 mins

• Regression tests: Passed

[Snuffleupagus]

The diff below should be a safe way to only overwrite the EXIF orientation, by "validating" the format of the data explicitly first.

However, as discussed, if it's safe to just replace the entire EXIF-block with fill-bytes (0xFF) that'd obviously be a lot easier and shorter by not requiring an EXIF parser.

diff --git a/external/exif-js/exif.js b/external/exif-js/exif.js
index 3bba4a643..97de3991f 100644
--- a/external/exif-js/exif.js
+++ b/external/exif-js/exif.js
@@ -75,8 +75,19 @@ function readTags(file, tiffStart, dirStart, strings, bigEnd) {
 
   for (let i = 0; i < entries; i++) {
     const entryOffset = dirStart + i * 12 + 2;
-    const tag = strings[file.getUint16(entryOffset, !bigEnd)];
+    const rawTag = file.getUint16(entryOffset, !bigEnd);
+    const tag = strings[rawTag];
     tags[tag] = readTagValue(file, entryOffset, tiffStart, dirStart, bigEnd);
+
+    //
+    if (rawTag === 0x0112 && bigEnd) {
+      const type = file.getUint16(entryOffset + 2, !bigEnd),
+        numValues = file.getUint32(entryOffset + 4, !bigEnd);
+
+      if (type === 3 && numValues === 1) {
+        tags[`_${tag}_offset`] = entryOffset + 8;
+      }
+    }
   }
   return tags;
 }
diff --git a/src/core/jpg.js b/src/core/jpg.js
index cf4e16193..88eb95021 100644
--- a/src/core/jpg.js
+++ b/src/core/jpg.js
@@ -847,7 +847,14 @@ class JpegImage {
               // Skip images with non-default orientation
               // (fixes bug1942064.pdf).
               if (exif.Orientation !== undefined && exif.Orientation !== 1) {
-                return false;
+                const orientionOffset = exif._Orientation_offset;
+
+                if (orientionOffset) {
+                  appData[orientionOffset] = 0x00;
+                  appData[orientionOffset + 1] = 0x01;
+                } else {
+                  return false;
+                }
               }
             }
           }