pdf2kindle patch

diff --git a/pdf2kindle.sh b/pdf2kindle.sh
index 3bb3a0a..f4d7235 100755
--- a/pdf2kindle.sh
+++ b/pdf2kindle.sh
@@ -57,9 +57,10 @@ do
                # TODO:実行速度が遅いので、どうにかしてOpenCV化したい
                convert \
                        $TMPDIR/pgm/$(basename $F) \
-                       -level '0%,100%' \
-                       -chop ${LEFT}x${TOP} -flip -flop \
-                       -chop ${RIGHT}x${BOTTOM} -flip -flop \
+                       -chop ${LEFT}x${TOP} \
+                       -gravity SouthEast \
+                       -chop ${RIGHT}x${BOTTOM} \
+                       -gravity NorthWest \
                        -fuzz 50% -trim \
                        -quality 0 \
                        $TMPDIR/png/$(basename $F .pgm).png \