Some additions to aos/vision/blob (transpose and move_scale).

Change-Id: I927144e27d0494f3ea879ebbd1647741f82e3c7b
diff --git a/aos/vision/blob/range_image.h b/aos/vision/blob/range_image.h
index 109a100..3647890 100644
--- a/aos/vision/blob/range_image.h
+++ b/aos/vision/blob/range_image.h
@@ -53,6 +53,8 @@
 
   int mini() const { return min_y_; }
 
+  int height() const { return min_y_ + ranges_.size(); }
+
  private:
   // minimum index in y where the blob starts
   int min_y_ = 0;