From 397ee492d922e2bc9c871ae964bfe440f582ce07 Mon Sep 17 00:00:00 2001
From: Lovell Fuller <github@lovell.info>
Date: Thu, 18 Apr 2024 11:05:04 +0100
Subject: [PATCH] Ensure extend op is sequential for multi-page TIFF #4069

---
 docs/changelog.md   |  3 +++
 src/pipeline.cc     |  1 +
 test/unit/extend.js | 47 +++++++++++++++++++++++++++++++--------------
 3 files changed, 37 insertions(+), 14 deletions(-)

diff --git a/docs/changelog.md b/docs/changelog.md
index 5361e5126..d3e63c8ae 100644
--- a/docs/changelog.md
+++ b/docs/changelog.md
@@ -18,6 +18,9 @@ Requires libvips v8.15.2
 * Expose `bilinear` resizing kernel (and interpolator).
   [#4061](https://github.com/lovell/sharp/issues/4061)
 
+* Ensure `extend` operation stays sequential for multi-page TIFF (regression in 0.32.0).
+  [#4069](https://github.com/lovell/sharp/issues/4069)
+
 ### v0.33.3 - 23rd March 2024
 
 * Upgrade to libvips v8.15.2 for upstream bug fixes.
diff --git a/src/pipeline.cc b/src/pipeline.cc
index a9c68f123..c80988cd2 100644
--- a/src/pipeline.cc
+++ b/src/pipeline.cc
@@ -566,6 +566,7 @@ class PipelineWorker : public Napi::AsyncWorker {
           std::vector<double> background;
           std::tie(image, background) = sharp::ApplyAlpha(image, baton->extendBackground, shouldPremultiplyAlpha);
 
+          image = sharp::StaySequential(image, baton->input->access, nPages > 1);
           image = nPages > 1
             ? sharp::EmbedMultiPage(image,
                 baton->extendLeft, baton->extendTop, baton->width, baton->height,
diff --git a/test/unit/extend.js b/test/unit/extend.js
index 4d57ba977..3ddbd0e14 100644
--- a/test/unit/extend.js
+++ b/test/unit/extend.js
@@ -73,20 +73,6 @@ describe('Extend', function () {
         });
     });
 
-    it('extend top with mirroring uses ordered read', async () => {
-      const data = await sharp(fixtures.inputJpg)
-        .extend({
-          extendWith: 'mirror',
-          top: 1
-        })
-        .png({ compressionLevel: 0 })
-        .toBuffer();
-
-      const { width, height } = await sharp(data).metadata();
-      assert.strictEqual(2725, width);
-      assert.strictEqual(2226, height);
-    });
-
     it(`extend sides unequally with RGBA (${extendWith})`, function (done) {
       sharp(fixtures.inputPngWithTransparency16bit)
         .resize(120)
@@ -127,6 +113,39 @@ describe('Extend', function () {
     });
   });
 
+  it('extend top with mirroring uses ordered read', async () => {
+    const data = await sharp(fixtures.inputJpg)
+      .extend({
+        extendWith: 'mirror',
+        top: 1
+      })
+      .png({ compressionLevel: 0 })
+      .toBuffer();
+
+    const { width, height } = await sharp(data).metadata();
+    assert.strictEqual(2725, width);
+    assert.strictEqual(2226, height);
+  });
+
+  it('multi-page extend uses ordered read', async () => {
+    const multiPageTiff = await sharp(fixtures.inputGifAnimated, { animated: true })
+      .resize({ width: 8, height: 48 })
+      .tiff()
+      .toBuffer();
+
+    const data = await sharp(multiPageTiff, { pages: -1 })
+      .extend({
+        background: 'red',
+        top: 1
+      })
+      .png({ compressionLevel: 0 })
+      .toBuffer();
+
+    const { width, height } = await sharp(data).metadata();
+    assert.strictEqual(8, width);
+    assert.strictEqual(1470, height);
+  });
+
   it('missing parameter fails', function () {
     assert.throws(function () {
       sharp().extend();