fix(core): re-apply invert after colormap when scrolling a stack

packages/core/src/RenderingEngine/StackViewport.ts

@@ -995,6 +995,15 @@ class StackViewport extends Viewport {
 
     if (typeof colormap !== 'undefined') {
       this.setColormap(colormap);
+      // setColormap rebuilds the RGB transfer function in its default,
+      // non-inverted state, so `this.invert` no longer reflects the actor's
+      // actual LUT. Clear the tracked flag so the setInvertColor below actually
+      // re-applies the inversion instead of being skipped by its no-op guard
+      // (setInvertColorGPU only flips the TF when the requested value differs
+      // from this.invert). Without this, invert is lost when scrolling after a
+      // reset: reset applies a colormap, which is then re-applied on every
+      // scroll and clobbers the inversion.
+      this.invert = false;
     }
 
     this.setInterpolationType(interpolationType);

packages/core/test/stackViewport_gpu_render_test.js

@@ -26,7 +26,8 @@ const { cache, RenderingEngine, utilities, imageLoader, metaData, Enums } =
   cornerstone3D;
 
 const { Events, ViewportType, InterpolationType } = Enums;
-const { calibratedPixelSpacingMetadataProvider } = utilities;
+const { calibratedPixelSpacingMetadataProvider, transferFunctionUtils } =
+  utilities;
 
 const { fakeImageLoader, fakeMetaDataProvider, compareImages } = testUtils;
 
@@ -916,6 +917,55 @@ describe('renderingCore -- Stack', () => {
         .catch(done.fail);
     });
 
+    it('Should preserve inversion when scrolling after resetProperties', function (done) {
+      testUtils.createViewports(renderingEngine, {
+        viewportId,
+        orientation: Enums.OrientationAxis.AXIAL,
+      });
+
+      const imageInfo = {
+        loader: 'fakeImageLoader',
+        name: 'imageURI',
+        rows: 64,
+        columns: 64,
+        barStart: 20,
+        barWidth: 5,
+        xSpacing: 1,
+        ySpacing: 1,
+        sliceIndex: 0,
+      };
+      const imageId1 = testUtils.encodeImageIdInfo(imageInfo);
+      const imageId2 = testUtils.encodeImageIdInfo({
+        ...imageInfo,
+        sliceIndex: 1,
+      });
+
+      const vp = renderingEngine.getViewport(viewportId);
+      const getTransferFunctionColors = () => {
+        const actor = vp.getDefaultActor().actor;
+        const transferFunction = actor.getProperty().getRGBTransferFunction(0);
+
+        return transferFunctionUtils
+          .getTransferFunctionNodes(transferFunction)
+          .map(([, red, green, blue]) => [red, green, blue]);
+      };
+
+      vp.setStack([imageId1, imageId2], 0)
+        .then(() => {
+          vp.resetProperties();
+          vp.setProperties({ invert: true });
+
+          const invertedColors = getTransferFunctionColors();
+
+          return vp.setImageIdIndex(1).then(() => {
+            expect(vp.getProperties().invert).toBe(true);
+            expect(getTransferFunctionColors()).toEqual(invertedColors);
+          });
+        })
+        .then(done)
+        .catch(done.fail);
+    });
+
     it('Should be able to resetProperties API', function (done) {
       const element = testUtils.createViewports(renderingEngine, {
         viewportId,