fix(imageIndex vs sliceIndex): imageIndex should be ijk based and slice index view based

common/reviews/api/core.api.md

@@ -2224,6 +2224,8 @@ interface IViewport {
     // (undocumented)
     getRotation: () => number;
     // (undocumented)
+    getSliceIndex(): number;
+    // (undocumented)
     getViewPresentation(viewPresSel?: ViewPresentationSelector): ViewPresentation;
     // (undocumented)
     getViewReference(viewRefSpecifier?: ViewReferenceSpecifier): ViewReference;
@@ -3131,6 +3133,8 @@ export class StackViewport extends Viewport implements StackViewport, IImagesLoa
     // (undocumented)
     getRotation: () => number;
     // (undocumented)
+    getSliceIndex: () => number;
+    // (undocumented)
     getTargetImageIdIndex: () => number;
     // (undocumented)
     getViewReference(viewRefSpecifier?: ViewReferenceSpecifier): ViewReference;
@@ -3623,6 +3627,8 @@ export class VideoViewport extends Viewport implements IVideoViewport {
     // (undocumented)
     protected getScalarData(): CanvasScalarData;
     // (undocumented)
+    getSliceIndex(): number;
+    // (undocumented)
     protected getTransform(): Transform;
     // (undocumented)
     getViewReference(viewRefSpecifier?: ViewReferenceSpecifier): ViewReference;
@@ -3798,6 +3804,8 @@ export class Viewport implements IViewport {
     // (undocumented)
     getRotation: () => number;
     // (undocumented)
+    getSliceIndex(): number;
+    // (undocumented)
     getViewPresentation(viewPresSel?: ViewPresentationSelector): ViewPresentation;
     // (undocumented)
     getViewReference(viewRefSpecifier?: ViewReferenceSpecifier): ViewReference;
@@ -4178,7 +4186,7 @@ export class VolumeViewport extends BaseVolumeViewport {
     // (undocumented)
     getCurrentImageId: () => string | undefined;
     // (undocumented)
-    getCurrentImageIdIndex: (volumeId?: string, useSlabThickness?: boolean) => number;
+    getCurrentImageIdIndex: (volumeId?: string) => number;
     // (undocumented)
     getNumberOfSlices: () => number;
     // (undocumented)

packages/core/src/RenderingEngine/BaseVolumeViewport.ts

@@ -614,7 +614,7 @@ abstract class BaseVolumeViewport extends Viewport implements IVolumeViewport {
     }
     const { viewPlaneNormal } = target;
     const delta =
-      (viewRefSpecifier.sliceIndex as number) - this.getCurrentImageIdIndex();
+      (viewRefSpecifier.sliceIndex as number) - this.getSliceIndex();
     // Calculate a camera focal point and position
     const { sliceRangeInfo } = getVolumeViewportScrollInfo(
       this,
@@ -657,7 +657,7 @@ abstract class BaseVolumeViewport extends Viewport implements IVolumeViewport {
     if (options?.withNavigation) {
       return true;
     }
-    const currentSliceIndex = this.getCurrentImageIdIndex();
+    const currentSliceIndex = this.getSliceIndex();
     const { sliceIndex } = viewRef;
     if (Array.isArray(sliceIndex)) {
       return (
@@ -1757,7 +1757,7 @@ abstract class BaseVolumeViewport extends Viewport implements IVolumeViewport {
       )?.uid;
     }
 
-    const currentIndex = this.getCurrentImageIdIndex();
+    const currentIndex = this.getSliceIndex();
     sliceIndex ??= currentIndex;
     const { viewPlaneNormal, focalPoint } = this.getCamera();
     const querySeparator = volumeId.indexOf('?') > -1 ? '&' : '?';

packages/core/src/RenderingEngine/StackViewport.ts

@@ -2880,6 +2880,14 @@ class StackViewport extends Viewport implements IStackViewport, IImagesLoader {
     return this.currentImageIdIndex;
   };
 
+  /**
+   * returns the slice index of the view
+   * @returns slice index
+   */
+  public getSliceIndex = (): number => {
+    return this.currentImageIdIndex;
+  };
+
   /**
    * Checks to see if this target is or could be shown in this viewport
    */

packages/core/src/RenderingEngine/VideoViewport.ts

@@ -735,7 +735,7 @@ class VideoViewport extends Viewport implements IVideoViewport {
     if (options.withNavigation) {
       return true;
     }
-    const currentIndex = this.getCurrentImageIdIndex();
+    const currentIndex = this.getSliceIndex();
     if (Array.isArray(sliceIndex)) {
       return currentIndex >= sliceIndex[0] && currentIndex <= sliceIndex[1];
     }
@@ -786,6 +786,10 @@ class VideoViewport extends Viewport implements IVideoViewport {
     return Math.round(this.videoElement.currentTime * this.fps);
   }
 
+  public getSliceIndex() {
+    return this.getCurrentImageIdIndex();
+  }
+
   public getCamera(): ICamera {
     const { parallelScale } = this.videoCamera;
 

packages/core/src/RenderingEngine/Viewport.ts

@@ -1097,6 +1097,10 @@ class Viewport implements IViewport {
     throw new Error('Not implemented');
   }
 
+  public getSliceIndex(): number {
+    throw new Error('Not implemented');
+  }
+
   /**
    * Gets a referenced image url of some sort - could be a real image id, or
    * could be a URL with parameters. Regardless it refers to the currently displaying
@@ -1611,7 +1615,7 @@ class Viewport implements IViewport {
       cameraFocalPoint,
       viewPlaneNormal,
       viewUp,
-      sliceIndex: viewRefSpecifier.sliceIndex ?? this.getCurrentImageIdIndex(),
+      sliceIndex: viewRefSpecifier.sliceIndex ?? this.getSliceIndex(),
     };
     return target;
   }

packages/core/src/RenderingEngine/VolumeViewport.ts

@@ -29,7 +29,7 @@ import setDefaultVolumeVOI from './helpers/setDefaultVolumeVOI';
 import { setTransferFunctionNodes } from '../utilities/transferFunctionUtils';
 import { ImageActor } from '../types/IActor';
 import getImageSliceDataForVolumeViewport from '../utilities/getImageSliceDataForVolumeViewport';
-import getVolumeViewportScrollInfo from '../utilities/getVolumeViewportScrollInfo';
+import { vec3 } from 'gl-matrix';
 
 /**
  * An object representing a VolumeViewport. VolumeViewports are used to render
@@ -92,15 +92,6 @@ class VolumeViewport extends BaseVolumeViewport {
     return numberOfSlices;
   };
 
-  /**
-   * Returns the image index associated with the volume viewport.
-   * @returns The image index.
-   */
-  public getSliceIndex = (): number => {
-    const { imageIndex } = getImageSliceDataForVolumeViewport(this);
-    return imageIndex;
-  };
-
   /**
    * Creates and adds volume actors for all volumes defined in the `volumeInputArray`.
    * For each entry, if a `callback` is supplied, it will be called with the new volume actor as input.
@@ -387,23 +378,52 @@ class VolumeViewport extends BaseVolumeViewport {
   }
 
   /**
-   * Uses the slice range information to compute the current image id index.
-   * Note that this may be offset from the origin location, or opposite in
-   * direction to the distance from the origin location, as the index is a
-   * complete index from minimum to maximum.
+   * Returns the imageId index of the current slice in the volume viewport.
+   * Note: this is not guaranteed to be the same as the slice index in the view
+   * To get the slice index in the view (scroll position), use getSliceIndex()
+   *
+   * In future we will even delete this method as it should not be used
+   * at all.
    *
    * @returns The slice index in the direction of the view
    */
-  public getCurrentImageIdIndex = (
-    volumeId?: string,
-    useSlabThickness = true
-  ): number => {
-    const { currentStepIndex } = getVolumeViewportScrollInfo(
-      this,
-      volumeId || this.getVolumeId(),
-      useSlabThickness
+  public getCurrentImageIdIndex = (volumeId?: string): number => {
+    const { viewPlaneNormal, focalPoint } = this.getCamera();
+
+    const imageData = this.getImageData(volumeId);
+
+    if (!imageData) {
+      return;
+    }
+
+    const { origin, direction, spacing } = imageData;
+
+    const spacingInNormal = getSpacingInNormalDirection(
+      { direction, spacing },
+      viewPlaneNormal
     );
-    return currentStepIndex;
+    const sub = vec3.create();
+    vec3.sub(sub, focalPoint, origin);
+    const distance = vec3.dot(sub, viewPlaneNormal);
+
+    // divide by the spacing in the normal direction to get the
+    // number of steps, and subtract 1 to get the index
+    return Math.round(Math.abs(distance) / spacingInNormal);
+  };
+
+  /**
+   * Returns the image index associated with the volume viewport in the current view, the difference
+   * between this method and getCurrentImageIdIndex is that this method returns the index of the
+   * slice in the volume in view direction so at the top (scrollbar top) of the viewport the index
+   * will be 0 and at the bottom (scrollbar bottom) the index will be the number of slices - 1.
+   * But the getCurrentImageIdIndex returns the index of current image in the imageIds
+   * which is not guaranteed to be the same as the slice index in the view.
+   *
+   * @returns The image index.
+   */
+  public getSliceIndex = (): number => {
+    const { imageIndex } = getImageSliceDataForVolumeViewport(this);
+    return imageIndex;
   };
 
   /**

packages/core/src/types/IViewport.ts

@@ -333,8 +333,10 @@ interface IViewport {
   ): boolean;
   /** Gets the number of slices in the current camera orientation */
   getNumberOfSlices(): number;
-  /** Gets the current slice in the current camera orientation */
+  /** Gets the index of the current image, it is not guaranteed to be the slice index in the view, use getSliceIndex for positional information */
   getCurrentImageIdIndex(): number;
+  /** gets the positional slice location in the view, similar to scrollbar, the top image is 0, the bottom is getNumberOfSlices - 1 */
+  getSliceIndex(): number;
   /**
    * Gets a referenced image url of some sort - could be a real image id, or
    * could be a URL with parameters. Regardless it refers to the currently displaying

packages/tools/examples/interpolationContourSegmentation/index.ts

@@ -201,7 +201,7 @@ function acceptCurrent() {
           segmentIndex:
             segmentation.segmentIndex.getActiveSegmentIndex(segmentationId),
           segmentationId: segmentationIdStack,
-          sliceIndex: viewport.getCurrentImageIdIndex(),
+          sliceIndex: viewport.getSliceIndex(),
         }
       );
     }