do not read out of range bits of the image

diff --git a/pctb/rgbimage.c b/pctb/rgbimage.c
index d0ba6b797442ef7e7b5c64f6d6d1f557c0c9cafd..c4fd11d470c9a06ea39cbf81eb647a4fe26b0698 100644 (file)
--- a/pctb/rgbimage.c
+++ b/pctb/rgbimage.c
@@ -89,7 +89,9 @@ static int identify1(const RgbImage *base, Rect portion,
          int c;
          dbassert( dbfile_scanf("%d",&c) == 1);
          dbassert(c>=0 && c<=255);
-         diff |= (c != RI_PIXEL(base, portion.tl.x + x, portion.tl.y + y)[i]);
+         int px= portion.tl.x + x, py= portion.tl.y + y;
+         diff |= px > portion.br.x || py > portion.br.y ||
+                 (c != RI_PIXEL(base,px,py)[i]);
        }
       }
     }