From a2314c4aa0db25fd2f812df439e3d5e8de8757c7 Mon Sep 17 00:00:00 2001
From: Lovell Fuller <github@lovell.info>
Date: Sat, 15 Feb 2020 11:46:13 +0000
Subject: [PATCH] Ensure RGBA LZW TIFF info.channel count #2064

---
 docs/changelog.md |  3 +++
 src/pipeline.cc   |  4 ++--
 test/unit/tiff.js | 37 +++++++++++++++++++++++++++++++++++++
 3 files changed, 42 insertions(+), 2 deletions(-)

diff --git a/docs/changelog.md b/docs/changelog.md
index 297b4b27..73e1fc78 100644
--- a/docs/changelog.md
+++ b/docs/changelog.md
@@ -9,6 +9,9 @@ Requires libvips v8.9.0.
 * Prevent use of sequentialRead for EXIF-based rotate operation.
   [#2042](https://github.com/lovell/sharp/issues/2042)
 
+* Ensure RGBA LZW TIFF returns correct channel count.
+  [#2064](https://github.com/lovell/sharp/issues/2064)
+
 ### v0.24.0 - 16<sup>th</sup> January 2020
 
 * Drop support for Node.js 8.
diff --git a/src/pipeline.cc b/src/pipeline.cc
index 5c38beae..c6c22a98 100644
--- a/src/pipeline.cc
+++ b/src/pipeline.cc
@@ -764,6 +764,7 @@ class PipelineWorker : public Nan::AsyncWorker {
           // Write TIFF to buffer
           if (baton->tiffCompression == VIPS_FOREIGN_TIFF_COMPRESSION_JPEG) {
             sharp::AssertImageTypeDimensions(image, ImageType::JPEG);
+            baton->channels = std::min(baton->channels, 3);
           }
           // Cast pixel values to float, if required
           if (baton->tiffPredictor == VIPS_FOREIGN_TIFF_PREDICTOR_FLOAT) {
@@ -786,7 +787,6 @@ class PipelineWorker : public Nan::AsyncWorker {
           area->free_fn = nullptr;
           vips_area_unref(area);
           baton->formatOut = "tiff";
-          baton->channels = std::min(baton->channels, 3);
         } else if (baton->formatOut == "heif" || (baton->formatOut == "input" && inputImageType == ImageType::HEIF)) {
           // Write HEIF to buffer
           VipsArea *area = VIPS_AREA(image.heifsave_buffer(VImage::option()
@@ -887,6 +887,7 @@ class PipelineWorker : public Nan::AsyncWorker {
           // Write TIFF to file
           if (baton->tiffCompression == VIPS_FOREIGN_TIFF_COMPRESSION_JPEG) {
             sharp::AssertImageTypeDimensions(image, ImageType::JPEG);
+            baton->channels = std::min(baton->channels, 3);
           }
           image.tiffsave(const_cast<char*>(baton->fileOut.data()), VImage::option()
             ->set("strip", !baton->withMetadata)
@@ -901,7 +902,6 @@ class PipelineWorker : public Nan::AsyncWorker {
             ->set("xres", baton->tiffXres)
             ->set("yres", baton->tiffYres));
           baton->formatOut = "tiff";
-          baton->channels = std::min(baton->channels, 3);
         } else if (baton->formatOut == "heif" || (mightMatchInput && isHeif) ||
           (willMatchInput && inputImageType == ImageType::HEIF)) {
           // Write HEIF to file
diff --git a/test/unit/tiff.js b/test/unit/tiff.js
index a5bf0208..5c11eb6a 100644
--- a/test/unit/tiff.js
+++ b/test/unit/tiff.js
@@ -208,11 +208,48 @@ describe('TIFF', function () {
       .toFile(fixtures.outputTiff, (err, info) => {
         if (err) throw err;
         assert.strictEqual('tiff', info.format);
+        assert.strictEqual(3, info.channels);
         assert(info.size < startSize);
         rimraf(fixtures.outputTiff, done);
       });
   });
 
+  it('TIFF LZW RGBA toFile', () =>
+    sharp({
+      create: {
+        width: 1,
+        height: 1,
+        channels: 4,
+        background: 'red'
+      }
+    })
+      .tiff({
+        compression: 'lzw'
+      })
+      .toFile(fixtures.outputTiff)
+      .then(info => {
+        assert.strictEqual(4, info.channels);
+      })
+  );
+
+  it('TIFF LZW RGBA toBuffer', () =>
+    sharp({
+      create: {
+        width: 1,
+        height: 1,
+        channels: 4,
+        background: 'red'
+      }
+    })
+      .tiff({
+        compression: 'lzw'
+      })
+      .toBuffer({ resolveWithObject: true })
+      .then(({ info }) => {
+        assert.strictEqual(4, info.channels);
+      })
+  );
+
   it('TIFF ccittfax4 compression shrinks b-w test file', function (done) {
     const startSize = fs.statSync(fixtures.inputTiff).size;
     sharp(fixtures.inputTiff)