feat(vtkimagedata.computehistogram): add numOfPixels to return value

Added the number of pixels involved in the calculation of the various values as part of the return
object. Also, added test cases to test computeHistogram().

Author: jadh4v

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

@@ -421,6 +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';