properly insert color changes

PyEmb.py

@@ -136,6 +136,9 @@ def write_embroidery_file(file_path, stitches):
 
     for stitch in stitches:
         if stitch.color != last_color:
+            if last_color is not None:
+                stitch.stop = True
+
             if stitch.color not in threads:
                 thread = make_thread(stitch.color)
                 thread_index = add_thread(pattern, thread)
@@ -150,8 +153,13 @@ def write_embroidery_file(file_path, stitches):
         libembroidery.embPattern_addStitchAbs(pattern, stitch.x - min_x, stitch.y - min_y, flags, 0)
 
         if flags & libembroidery.JUMP:
-            # I'm not sure this is right, but this is how the old version did it.
-            libembroidery.embPattern_addStitchAbs(pattern, stitch.x - min_x, stitch.y - min_y, flags & ~libembroidery.JUMP, 0)
+            # In C, I'd do flags &= ~(libembroidery.JUMP|libembroidery.STOP).
+            # Python bitwise not (~) works on signed integers, which really
+            # isn't what we want.  This is effectively the same:
+            flags &= 0xFFFF - (libembroidery.JUMP|libembroidery.STOP)
+
+            # I'm not sure this is right, but the old version added a stitch after the jump.
+            libembroidery.embPattern_addStitchRel(pattern, 0, 0, flags, 0)
 
     libembroidery.embPattern_addStitchAbs(pattern, stitch.x - min_x, stitch.y - min_y, libembroidery.END, 0)