diff --git a/core/src/com/google/zxing/common/BaseMonochromeBitmapSource.java b/core/src/com/google/zxing/common/BaseMonochromeBitmapSource.java
index 819274e59..b9de750ff 100644
--- a/core/src/com/google/zxing/common/BaseMonochromeBitmapSource.java
+++ b/core/src/com/google/zxing/common/BaseMonochromeBitmapSource.java
@@ -127,4 +127,8 @@ public abstract class BaseMonochromeBitmapSource implements MonochromeBitmapSour
 
   public abstract int getWidth();
 
+  public abstract int getLuminance(int x, int y);
+
+  public abstract void cacheRowForLuminance(int y);
+
 }