do not ignore height parameter of sensor if given and therefore do not force square sensor pixels (#20)

Author: rgerum

cameratransform/projection.py

@@ -124,7 +124,10 @@ def __init__(self, focallength_px=None, focallength_x_px=None, focallength_y_px=
         elif focallength_mm is not None and sensor_width_mm is not None:
             focallength_px = focallength_mm / sensor_width_mm * image_width_px
             focallength_x_px = focallength_px
-            focallength_y_px = focallength_px
+            if sensor_height_mm is not None:
+                focallength_y_px = focallength_mm / sensor_height_mm * image_height_px
+            else:
+                focallength_y_px = focallength_px
 
         self.parameters = ParameterSet(
             # the intrinsic parameters