[babl] babl: improve alpha calc. in pal+alpha -> rgba conversion

[N/A <ell src gnome org>]

commit ce0ec9123bd65de192296b4d09f7f3427bf73ffc
Author: Ell <ell_se yahoo com>
Date:   Sat Sep 30 07:44:41 2017 -0400

    babl: improve alpha calc. in pal+alpha -> rgba conversion
    
    ... in particular, so that fully opaque pixels remain fully opaque

 babl/babl-palette.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/babl/babl-palette.c b/babl/babl-palette.c
index 8b8e529..823ff0c 100644
--- a/babl/babl-palette.c
+++ b/babl/babl-palette.c
@@ -413,7 +413,7 @@ pala_u8_to_rgba_u8 (Babl          *conversion,
 
       palpx = pal->data_u8 + idx * 4;
       memcpy (dst, palpx, sizeof(char)*4);
-      dst[3] = (dst[3] * src[1]) >> 8;
+      dst[3] = (dst[3] * src[1] + 128) / 255;
 
       src += sizeof (char) * 2;
       dst += sizeof (char) * 4;