Fix merge size calc, fixes #1846

src/image/geometry.js

@@ -632,7 +632,7 @@ export function getSliceGeometrySpacing(origins) {
 }
 
 /**
- * Merge two geometries into one using the largest size and
+ * Merge two geometries into one using the merge size and
  *   smallest resolution.
  *
  * @param {Geometry} geometry1 The first geometry.
@@ -647,25 +647,35 @@ export function mergeGeometries(geometry1, geometry2) {
     return array1.map((v, i) => Math.max(v, array2[i]));
   };
 
-  const newSize = new Size(maxByIndex(
-    geometry1.getSize().getValues(),
-    geometry2.getSize().getValues()
-  ));
   const newSpacing = new Spacing(minByIndex(
     geometry1.getSpacing().getValues(),
     geometry2.getSpacing().getValues()
   ));
 
   const range1 = geometry1.getRange();
   const range2 = geometry2.getRange();
-  const minValues = minByIndex(
+  const minRangeValues = minByIndex(
     range1[0].getValues(),
     range2[0].getValues()
   );
+  const maxRangeValues = maxByIndex(
+    range1[1].getValues(),
+    range2[1].getValues()
+  );
+
+  const sizeValues = [];
+  for (let i = 0; i < minRangeValues.length; ++i) {
+    sizeValues.push(Math.round(
+      Math.abs(maxRangeValues[i] - minRangeValues[i]) / newSpacing.get(i)
+    ));
+  }
+  const newSize = new Size(sizeValues);
+
+  // TODO incorporate orientation
   const newOrigins = [];
   for (let i = 0; i < newSize.get(2); ++i) {
-    const values = minValues.slice();
-    values[2] = minValues[2] + i * newSpacing.get(2);
+    const values = minRangeValues.slice();
+    values[2] = minRangeValues[2] + i * newSpacing.get(2);
     newOrigins.push(new Point3D(
       values[0], values[1], values[2]
     ));