[babl] extensions-gggl: clamp when converting float to 16bit

[Øyvind Kolås <ok src gnome org>]

commit 6da8f5e755f02ca3c3fb2c625da78612cff7775d
Author: Øyvind Kolås <pippin gimp org>
Date:   Wed Dec 20 03:22:22 2017 +0100

    extensions-gggl: clamp when converting float to 16bit
    
    Improve the quality of a conversion that was picked in error for bug #790658

 extensions/gggl.c |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletions(-)
---
diff --git a/extensions/gggl.c b/extensions/gggl.c
index cf83988..625d730 100644
--- a/extensions/gggl.c
+++ b/extensions/gggl.c
@@ -543,7 +543,12 @@ conv_rgbaF_rgb16 (const Babl *conversion,unsigned char *src, unsigned char *dst,
 
       for (c = 0; c < 3; c++)
         {
-          *(unsigned short *) dst = lrint ((*(float *) src) * 65535.0);
+          if ((*(float *) src) >= 1.0)
+            *(unsigned short *) dst = 65535;
+          else if ((*(float *) src) <=0)
+            *(unsigned short *) dst = 0;
+          else
+            *(unsigned short *) dst = lrint ((*(float *) src) * 65535.0);
           dst                    += 2;
           src                    += 4;
         }