From 6f9699f605e9436fef94e1afc113f63e57e719be Mon Sep 17 00:00:00 2001
From: Lovell Fuller <github@lovell.info>
Date: Mon, 19 Nov 2018 20:00:30 +0000
Subject: [PATCH] Ensure correct channel info for raw, greyscale output #1425

---
 docs/changelog.md | 3 +++
 src/pipeline.cc   | 1 +
 test/unit/io.js   | 1 +
 3 files changed, 5 insertions(+)

diff --git a/docs/changelog.md b/docs/changelog.md
index 6cf3f3b1..6c11b1cb 100644
--- a/docs/changelog.md
+++ b/docs/changelog.md
@@ -10,6 +10,9 @@ Requires libvips v8.7.0.
   [#1422](https://github.com/lovell/sharp/pull/1422)
   [@SethWen](https://github.com/SethWen)
 
+* Ensure `channel` metadata is correct for raw, greyscale output.
+  [#1425](https://github.com/lovell/sharp/issues/1425)
+
 * Add support for the "mitchell" kernel for image reductions.
   [#1438](https://github.com/lovell/sharp/pull/1438)
   [@Daiz](https://github.com/Daiz)
diff --git a/src/pipeline.cc b/src/pipeline.cc
index d230b1e4..e5fcf87b 100644
--- a/src/pipeline.cc
+++ b/src/pipeline.cc
@@ -771,6 +771,7 @@ class PipelineWorker : public Nan::AsyncWorker {
           if (baton->greyscale || image.interpretation() == VIPS_INTERPRETATION_B_W) {
             // Extract first band for greyscale image
             image = image[0];
+            baton->channels = 1;
           }
           if (image.format() != VIPS_FORMAT_UCHAR) {
             // Cast pixels to uint8 (unsigned char)
diff --git a/test/unit/io.js b/test/unit/io.js
index 6dbce452..d2bd0980 100644
--- a/test/unit/io.js
+++ b/test/unit/io.js
@@ -1388,6 +1388,7 @@ describe('Input/output', function () {
           assert.strictEqual('raw', info.format);
           assert.strictEqual(32, info.width);
           assert.strictEqual(24, info.height);
+          assert.strictEqual(1, info.channels);
           done();
         });
     });