Improve variable names and comments in blob code

No functional changes whatsoever.

Change-Id: I71f7d106c2e6eb371a248f7e47ed15f152566f6f
diff --git a/aos/vision/blob/find_blob.h b/aos/vision/blob/find_blob.h
index b167c3e..d633354 100644
--- a/aos/vision/blob/find_blob.h
+++ b/aos/vision/blob/find_blob.h
@@ -1,5 +1,5 @@
-#ifndef _AOS_VISION_BLOB_FIND_BLOB_H_
-#define _AOS_VISION_BLOB_FIND_BLOB_H_
+#ifndef AOS_VISION_BLOB_FIND_BLOB_H_
+#define AOS_VISION_BLOB_FIND_BLOB_H_
 
 #include "aos/vision/blob/range_image.h"
 
@@ -8,9 +8,9 @@
 
 // Uses disjoint sets to group ranges into disjoint RangeImage.
 // ranges that overlap are grouped into the same output RangeImage.
-BlobList FindBlobs(const RangeImage &rimg);
+BlobList FindBlobs(const RangeImage &input_image);
 
 }  // namespace vision
 }  // namespace aos
 
-#endif  // _AOS_VISION_BLOB_FIND_BLOB_H_
+#endif  // AOS_VISION_BLOB_FIND_BLOB_H_