diff --git a/ReactionRecorder.cs b/ReactionRecorder.cs
--- a/ReactionRecorder.cs
+++ b/ReactionRecorder.cs
@@ -313,9 +313,9 @@ namespace DesertPaintLab
 
             bool result = true;
 
-            int solidUpperLeft = testPixelStart + ((y+2) * stride) + ((x+2) * 3);
-            int solidLowerLeft = testPixelStart + ((swatchHeight - 4) * stride);
-            int solidUpperRight = testPixelStart + ((swatchWidth - 4) * 3);
+            int solidUpperLeft = testPixelStart + (2 * stride) + (2 * 3);
+            int solidLowerLeft = solidUpperLeft + ((swatchHeight - 4) * stride);
+            int solidUpperRight = solidUpperLeft + ((swatchWidth - 4) * 3);
             int solidLowerRight = solidLowerLeft + ((swatchWidth - 4) * 3);
             byte swatch_r = pixBytes[solidUpperLeft];
             byte swatch_g = pixBytes[solidUpperLeft + 1];