Merge pull request #2158 from jadh4v/add-numOfPixels-to-vtkImageData-computeHistogram

feat(vtkImageData.computeHistogram): added number of pixels involved

Author: floryst

Sources/Common/DataModel/ImageData/index.d.ts

@@ -22,7 +22,7 @@ interface IComputeHistogram {
 export interface vtkImageData extends vtkDataSet {
 
 	/**
-	 * Returns an object with `{ minimum, maximum, average, variance, sigma }`
+	 * Returns an object with `{ minimum, maximum, average, variance, sigma, count }`
 	 * of the imageData points found within the provided `worldBounds`.
 	 *
 	 * `voxelFunc(index, bounds)` is an optional function that is called with

Sources/Common/DataModel/ImageData/index.js

@@ -410,7 +410,9 @@ function vtkImageData(publicAPI, model) {
     }
 
     const average = inum > 0 ? isum / inum : 0;
-    const variance = sumOfSquares - average * average;
+    const variance = inum
+      ? Math.abs(sumOfSquares / inum - average * average)
+      : 0;
     const sigma = Math.sqrt(variance);
 
     return {
@@ -419,6 +421,7 @@ function vtkImageData(publicAPI, model) {
       average,
       variance,
       sigma,
+      count: inum,
     };
   };
 

Sources/Common/DataModel/ImageData/test/testImageData.js

@@ -0,0 +1,107 @@
+import test from 'tape-catch';
+import vtkImageData from 'vtk.js/Sources/Common/DataModel/ImageData';
+import vtkRTAnalyticSource from 'vtk.js/Sources/Filters/Sources/RTAnalyticSource';
+
+test('Test vtkImageData instance', (t) => {
+  t.ok(vtkImageData, 'Make sure the class definition exists');
+  const instance = vtkImageData.newInstance();
+  t.ok(instance);
+  t.end();
+});
+
+test('Test vtkImageData histogram', (t) => {
+  const spacing = 0.7;
+  const size = 50;
+  const compareFloat = (a, b) => Math.abs(a - b) < Number.EPSILON;
+
+  const source = vtkRTAnalyticSource.newInstance();
+  source.setWholeExtent([0, size, 0, size, 0, size]);
+  source.update();
+
+  const image = source.getOutputData();
+  image.setSpacing([spacing, spacing, spacing]);
+
+  const bounds = image.getBounds();
+  const hist = image.computeHistogram(bounds);
+
+  const baseline1 = {
+    minimum: 9,
+    maximum: 185,
+    average: 64.65,
+    variance: 782.87,
+    sigma: 27.98,
+    count: 132651,
+  };
+
+  t.ok(
+    hist.minimum === baseline1.minimum,
+    'computeHistogram return value test: minimum'
+  );
+  t.ok(
+    hist.maximum === baseline1.maximum,
+    'computeHistogram return value test: maximum'
+  );
+  t.ok(
+    compareFloat(hist.average.toFixed(2), baseline1.average),
+    'computeHistogram return value test: average'
+  );
+  t.ok(
+    compareFloat(hist.variance.toFixed(2), baseline1.variance),
+    'computeHistogram return value test: variance'
+  );
+  t.ok(
+    compareFloat(hist.sigma.toFixed(2), baseline1.sigma),
+    'computeHistogram return value test: sigma'
+  );
+  t.ok(
+    hist.count === baseline1.count,
+    'computeHistogram return value test: count'
+  );
+
+  // masking function that ignores the bottom 10 and top 10 rows of voxels.
+  const voxelFunc = (idx) => idx[0] > 9 && idx[0] < 40;
+
+  const baseline2 = {
+    minimum: 9,
+    maximum: 173,
+    average: 65.29,
+    variance: 676.51,
+    sigma: 26.01,
+    count: 78030,
+  };
+
+  const histWithMask = image.computeHistogram(bounds, voxelFunc);
+
+  t.ok(
+    histWithMask.minimum === baseline2.minimum &&
+      histWithMask.maximum === baseline2.maximum &&
+      compareFloat(histWithMask.average.toFixed(2), baseline2.average) &&
+      compareFloat(histWithMask.variance.toFixed(2), baseline2.variance) &&
+      compareFloat(histWithMask.sigma.toFixed(2), baseline2.sigma) &&
+      histWithMask.count === baseline2.count,
+    'computeHistogram test with masking function'
+  );
+
+  const voxelFuncNone = (idx) => false;
+  const baseline3 = {
+    minimum: Infinity,
+    maximum: -Infinity,
+    average: 0,
+    variance: 0,
+    sigma: 0,
+    count: 0,
+  };
+  const histNone = image.computeHistogram(bounds, voxelFuncNone);
+
+  t.ok(
+    histNone.minimum === baseline3.minimum &&
+      histNone.maximum === baseline3.maximum &&
+      compareFloat(histNone.average.toFixed(2), baseline3.average) &&
+      compareFloat(histNone.variance.toFixed(2), baseline3.variance) &&
+      compareFloat(histNone.sigma.toFixed(2), baseline3.sigma) &&
+      histNone.count === baseline3.count,
+    'computeHistogram test with zero number of voxels that qualify'
+  );
+
+  t.end();
+});

Sources/tests.js

@@ -17,6 +17,7 @@ import './Common/DataModel/Box/test/testBox';
 import './Common/DataModel/Cell/test/testCell';
 import './Common/DataModel/Cone/test/testConeImplicitFunction';
 import './Common/DataModel/DataSetAttributes/test/testDataSetAttributes';
+import './Common/DataModel/ImageData/test/testImageData';
 import './Common/DataModel/Line/test/testLine';
 import './Common/DataModel/Plane/test/testPlane';
 import './Common/DataModel/PolyData/test/testPolyData';