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alpha: scale and clamp alpha to its full extend

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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.
This commit is contained in:
Wim Taymans 2009-12-24 22:50:31 +01:00 committed by Wim Taymans
parent a65240d1c1
commit 0620797a18
1 changed files with 5 additions and 3 deletions
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8
gst/alpha/gstalpha.c
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@ -210,6 +210,7 @@ gst_alpha_base_init (gpointer g_class)
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 @@ gst_alpha_set_property (GObject * object, guint prop_id,
break;
}
}
static void
gst_alpha_get_property (GObject * object, guint prop_id, GValue * value,
GParamSpec * pspec)
@ -470,12 +472,12 @@ static void
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 @@ static void
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;