commit 0620797a18b3cf72a69b64d25332ef0be719f223
author Wim Taymans <wim.taymans@collabora.co.uk> Thu Dec 24 22:50:31 2009 +0100
committer Wim Taymans <wim@metal.(none)> Thu Dec 24 22:50:31 2009 +0100
tree d9372946fd35414432add18292fa90d3f2e19788
parent a65240d1c148599e431bf2f0892dfaa507e73ae6

alpha: scale and clamp alpha to its full extend

Convert the alpha value to 0->255 when setting and to 0->256 when using as
a scaling factor. This makes sure we can reach the full opacity value of 0xff in
all cases.

gst/alpha/gstalpha.c

diff --git a/gst/alpha/gstalpha.c b/gst/alpha/gstalpha.c
index 01bcbde..6aa1f8a 100644
--- a/gst/alpha/gstalpha.c
+++ b/gst/alpha/gstalpha.c
@@ -210,6 +210,7 @@
   GST_DEBUG_CATEGORY_INIT (gst_alpha_debug, "alpha", 0,
       "alpha - Element for adding alpha channel to streams");
 }
+
 static void
 gst_alpha_class_init (GstAlphaClass * klass)
 {
@@ -347,6 +348,7 @@
       break;
   }
 }
+
 static void
 gst_alpha_get_property (GObject * object, guint prop_id, GValue * value,
     GParamSpec * pspec)
@@ -470,12 +472,12 @@
 gst_alpha_set_ayuv (guint8 * src, guint8 * dest, gint width, gint height,
     gdouble alpha)
 {
-  gint b_alpha = (gint) (alpha * 255);
+  gint s_alpha = CLAMP ((gint) (alpha * 256), 0, 256);
   gint y, x;
 
   for (y = 0; y < height; y++) {
     for (x = 0; x < width; x++) {
-      *dest++ = (*src++ * b_alpha) >> 8;
+      *dest++ = (*src++ * s_alpha) >> 8;
       *dest++ = *src++;
       *dest++ = *src++;
       *dest++ = *src++;
@@ -487,7 +489,7 @@
 gst_alpha_set_i420 (guint8 * src, guint8 * dest, gint width, gint height,
     gdouble alpha)
 {
-  gint b_alpha = (gint) (alpha * 255);
+  gint b_alpha = CLAMP ((gint) (alpha * 255), 0, 255);
   guint8 *srcY;
   guint8 *srcU;
   guint8 *srcV;