@@ -94,7 +94,10 @@ class PipelineWorker : public Napi::AsyncWorker {
       // Calculate angle of rotation
       VipsAngle rotation = VIPS_ANGLE_D0;
       VipsAngle autoRotation = VIPS_ANGLE_D0;
+      VipsAngle gainMapRotation = VIPS_ANGLE_D0;
       bool autoFlop = false;
+      bool gainMapFlip = false;
+      bool gainMapFlop = false;
 
       if (baton->input->autoOrient) {
         // Rotate and flip image according to Exif orientation
@@ -115,11 +118,13 @@ class PipelineWorker : public Napi::AsyncWorker {
             MultiPageUnsupported(nPages, "Rotate");
           }
           image = image.rot(autoRotation);
+          gainMapRotation = autoRotation;
           autoRotation = VIPS_ANGLE_D0;
         }
         if (autoFlop) {
           image = image.flip(VIPS_DIRECTION_HORIZONTAL);
           autoFlop = false;
+          gainMapFlop = true;
         }
       }
 
@@ -128,20 +133,24 @@ class PipelineWorker : public Napi::AsyncWorker {
         if (baton->flip) {
           image = image.flip(VIPS_DIRECTION_VERTICAL);
           baton->flip = false;
+          gainMapFlip = true;
         }
         if (baton->flop) {
           image = image.flip(VIPS_DIRECTION_HORIZONTAL);
           baton->flop = false;
+          gainMapFlop = true;
         }
         if (rotation != VIPS_ANGLE_D0) {
           if (rotation != VIPS_ANGLE_D180) {
             MultiPageUnsupported(nPages, "Rotate");
           }
           image = image.rot(rotation);
+          gainMapRotation = rotation;
           rotation = VIPS_ANGLE_D0;
         }
         if (baton->rotationAngle != 0.0) {
           MultiPageUnsupported(nPages, "Rotate");
+          KeepGainMapUnsupported(baton->keepGainMap, "Rotate");
           std::vector<double> background;
           std::tie(image, background) = sharp::ApplyAlpha(image, baton->rotationBackground, false);
           image = image.rotate(baton->rotationAngle, VImage::option()->set("background", background)).copy_memory();
@@ -307,6 +316,15 @@ class PipelineWorker : public Napi::AsyncWorker {
           if (image.get_typeof("gainmap-scale-factor") == G_TYPE_INT) {
             gainMapScaleFactor = image.get_int("gainmap-scale-factor");
           }
+          if (gainMapFlip) {
+            gainMap = gainMap.flip(VIPS_DIRECTION_VERTICAL);
+          }
+          if (gainMapFlop) {
+            gainMap = gainMap.flip(VIPS_DIRECTION_HORIZONTAL);
+          }
+          if (gainMapRotation != VIPS_ANGLE_D0) {
+            gainMap = gainMap.rot(gainMapRotation);
+          }
           if (baton->topOffsetPre != -1) {
             gainMap = gainMap.extract_area(
               baton->leftOffsetPre / gainMapScaleFactor, baton->topOffsetPre / gainMapScaleFactor,
@@ -563,6 +581,7 @@ class PipelineWorker : public Napi::AsyncWorker {
       // Rotate post-extract non-90 angle
       if (!baton->rotateBefore && baton->rotationAngle != 0.0) {
         MultiPageUnsupported(nPages, "Rotate");
+        KeepGainMapUnsupported(baton->keepGainMap, "Rotate");
         image = sharp::StaySequential(image);
         std::vector<double> background;
         std::tie(image, background) = sharp::ApplyAlpha(image, baton->rotationBackground, shouldPremultiplyAlpha);
 
@@ -259,8 +259,57 @@ suite('Gain maps', () => {
     );
   });
 
+  test('Can be detached, rotated and reattached', async (t) => {
+    t.plan(4);
+
+    const data = await sharp(fixtures.inputJpgWithGainMap)
+      .keepGainMap()
+      .rotate(90)
+      .extract({ left: 2000, top: 3000, width: 48, height: 32 })
+      .toBuffer();
+
+    const metadata = await sharp(data).metadata();
+    t.assert.strictEqual(metadata.format, 'jpeg');
+    t.assert.strictEqual(typeof metadata.gainMap, 'object');
+    t.assert.ok(Buffer.isBuffer(metadata.gainMap.image));
+
+    const {
+      format,
+      width,
+      height,
+      channels,
+      depth,
+      space,
+      hasProfile,
+      chromaSubsampling,
+    } = await sharp(metadata.gainMap.image).metadata();
+
+    t.assert.deepEqual(
+      {
+        format,
+        width,
+        height,
+        channels,
+        depth,
+        space,
+        hasProfile,
+        chromaSubsampling,
+      },
+      {
+        format: 'jpeg',
+        width: 12,
+        height: 8,
+        channels: 1,
+        depth: 'uchar',
+        space: 'b-w',
+        hasProfile: false,
+        chromaSubsampling: '4:4:4',
+      },
+    );
+  });
+
   test('Cannot keep existing gain map with certain operations', async (t) => {
-    t.plan(3);
+    t.plan(4);
 
     await t.assert.rejects(
       sharp(fixtures.inputJpgWithGainMap)
@@ -289,6 +338,14 @@ suite('Gain maps', () => {
         .toBuffer(),
       /Trim is not supported when keeping gain maps/
     );
+
+    await t.assert.rejects(
+      sharp(fixtures.inputJpgWithGainMap)
+        .keepGainMap()
+        .rotate(1)
+        .toBuffer(),
+      /Rotate is not supported when keeping gain maps/
+    );
   });
 
   test('other metadata can be retained when keeping gain map', async (t) => {