From 6433a64f4cd41e88499386b0b7c7ae05d30683b8 Mon Sep 17 00:00:00 2001

From: Tom Hughes <tom@compton.nu>

Date: Sat, 22 Jun 2013 12:33:32 +0100

Subject: [PATCH 14/15] Avoid potential zero division resulting in nan in

 agg::gamma_linear

---

 include/agg_gamma_functions.h | 6 +++++-

 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/include/agg_gamma_functions.h b/include/agg_gamma_functions.h

index fa38a45..beb0c04 100644

--- a/include/agg_gamma_functions.h

+++ b/include/agg_gamma_functions.h

@@ -94,7 +94,11 @@ namespace agg

         {

             if(x < m_start) return 0.0;

             if(x > m_end) return 1.0;

-            return (x - m_start) / (m_end - m_start);

+            double delta = m_end - m_start;

+            // avoid nan from potential zero division

+            // https://github.com/mapnik/mapnik/issues/761

+            if (delta <= 0.0) return 0.0;

+            return (x - m_start) / delta;

         }

     private:

-- 

1.8.1.4