fix(ImageMapper): Provide reasonable default if no function

Author: scottwittenburg

Sources/Rendering/OpenGL/ImageMapper/index.js

@@ -690,18 +690,23 @@ function vtkOpenGLImageMapper(publicAPI, model) {
 
         for (let c = 0; c < numIComps; ++c) {
           pwfun = actorProperty.getPiecewiseFunction(c);
-          const pwfRange = pwfun.getRange();
-          pwfun.getTable(pwfRange[0], pwfRange[1], pwfWidth, tmpTable, 1);
-          // adjust for sample distance etc
-          if (iComps) {
-            for (let i = 0; i < pwfWidth; i++) {
-              pwfFloatTable[c * pwfWidth * 2 + i] = 255.0 * tmpTable[i];
-              pwfFloatTable[c * pwfWidth * 2 + i + pwfWidth] =
-                255.0 * tmpTable[i];
-            }
+          if (pwfun === null) {
+            // Piecewise constant max if no function supplied for this component
+            pwfFloatTable.fill(255.0);
           } else {
-            for (let i = 0; i < pwfWidth; i++) {
-              pwfFloatTable[c * pwfWidth * 2 + i] = 255.0 * tmpTable[i];
+            const pwfRange = pwfun.getRange();
+            pwfun.getTable(pwfRange[0], pwfRange[1], pwfWidth, tmpTable, 1);
+            // adjust for sample distance etc
+            if (iComps) {
+              for (let i = 0; i < pwfWidth; i++) {
+                pwfFloatTable[c * pwfWidth * 2 + i] = 255.0 * tmpTable[i];
+                pwfFloatTable[c * pwfWidth * 2 + i + pwfWidth] =
+                  255.0 * tmpTable[i];
+              }
+            } else {
+              for (let i = 0; i < pwfWidth; i++) {
+                pwfFloatTable[c * pwfWidth * 2 + i] = 255.0 * tmpTable[i];
+              }
             }
           }
         }