JP-2944: Limit major axis expansion for MIRI shower flagging

CHANGES.rst

@@ -16,6 +16,8 @@ dark_current
 
 jump
 ~~~~
+-- Changes to limit the expansion of MIRI shower ellipses to be the same
+number of pixels for both the major and minor axis. JP-2944 [#123]
 
 - Changes to flag both NIR snowballs and MIRI showers
 for  JP-#2645. [#118]

src/stcal/jump/jump.py

@@ -407,11 +407,19 @@ def extend_ellipses(plane, ellipses, sat_flag, jump_flag, expansion=1.1):
     for ellipse in ellipses:
         ceny = ellipse[0][0]
         cenx = ellipse[0][1]
-        majaxis = ellipse[1][0] * expansion
-        minaxis = ellipse[1][1] * expansion
+        # Expand the ellipse by the expansion factor. The number of pixels added to both axes is
+        # the number of pixels added to the minor axis. This prevents very large flagged ellipses
+        # with high axis ratio ellipses. The major and minor axis are not always the same index.
+        # Therefore, we have to test to find which is actually the minor axis.
+        if ellipse[1][1] < ellipse[1][0]:
+            axis1 = ellipse[1][0] + (expansion - 1.0) * ellipse[1][1]
+            axis2 = ellipse[1][1] * expansion
+        else:
+            axis1 = ellipse[1][0] * expansion
+            axis2 = ellipse[1][1] + (expansion - 1.0) * ellipse[1][0]
         alpha = ellipse[2]
-        image = cv.ellipse(image, (round(ceny), round(cenx)), (round(majaxis / 2),
-                           round(minaxis / 2)), alpha, 0, 360, (0, 0, 4), -1)
+        image = cv.ellipse(image, (round(ceny), round(cenx)), (round(axis1 / 2),
+                           round(axis2 / 2)), alpha, 0, 360, (0, 0, 4), -1)
         jump_ellipse = image[:, :, 2]
         saty, satx = np.where(sat_pix == 2)
         jump_ellipse[saty, satx] = 0