X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ian/git?a=blobdiff_plain;f=pattern.c;fp=pattern.c;h=e5f958abb817a600f10b1f9985ca2fd095380b7c;hb=ff218728c6953ede1957ddb5b039bcb2ba920a44;hp=ece1ed476e562913941b64b6d74409a35a91e9d7;hpb=b8313181a6104624000e9cc008e8e26b67aeb655;p=sgt-puzzles.git

diff --git a/pattern.c b/pattern.c
index ece1ed4..e5f958a 100644
--- a/pattern.c
+++ b/pattern.c
@@ -308,7 +308,18 @@ static void generate(random_state *rs, int w, int h, unsigned char *retgrid)
     fgrid2 = snewn(w*h, float);
     memcpy(fgrid2, fgrid, w*h*sizeof(float));
     qsort(fgrid2, w*h, sizeof(float), float_compare);
-    threshold = fgrid2[w*h/2];
+    /* Choose a threshold that makes half the pixels black. In case of
+     * an odd number of pixels, select randomly between just under and
+     * just over half. */
+    {
+        int index = w * h / 2;
+        if (w & h & 1)
+            index += random_upto(rs, 2);
+        if (index < w*h)
+            threshold = fgrid2[index];
+        else
+            threshold = fgrid2[w*h-1] + 1;
+    }
     sfree(fgrid2);
 
     for (i = 0; i < h; i++) {