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fix alpha multiplication routine to perhaps work correctly, reported by

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2002-04-09  Havoc Pennington  <hp@pobox.com>

	* src/theme.c (multiply_alpha): fix alpha multiplication routine
	to perhaps work correctly, reported by tigert. Also, be sure
	we always copy the image if necessary before modifying the
	alpha channel.
This commit is contained in:
Havoc Pennington 2002-04-10 04:00:32 +00:00 committed by Havoc Pennington
parent fa0592ebc7
commit 38ff6a49c4
2 changed files with 27 additions and 8 deletions
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7
ChangeLog
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@ -1,3 +1,10 @@
2002-04-09 Havoc Pennington <hp@pobox.com>
* src/theme.c (multiply_alpha): fix alpha multiplication routine
to perhaps work correctly, reported by tigert. Also, be sure
we always copy the image if necessary before modifying the
alpha channel.
2002-04-05 Havoc Pennington <hp@pobox.com>
* src/stack.c: remove the unused tab stuff

28
src/theme.c
View File

@ -2460,7 +2460,8 @@ get_gc_for_primitive (GtkWidget *widget,
static GdkPixbuf*
multiply_alpha (GdkPixbuf *pixbuf,
guchar alpha)
guchar alpha,
gboolean force_copy)
{
GdkPixbuf *new_pixbuf;
guchar *pixels;
@ -2469,7 +2470,7 @@ multiply_alpha (GdkPixbuf *pixbuf,
int row;
g_return_val_if_fail (GDK_IS_PIXBUF (pixbuf), NULL);
if (alpha == 255)
return pixbuf;
@ -2479,7 +2480,15 @@ multiply_alpha (GdkPixbuf *pixbuf,
g_object_unref (G_OBJECT (pixbuf));
pixbuf = new_pixbuf;
}
else if (force_copy)
{
new_pixbuf = gdk_pixbuf_copy (pixbuf);
g_object_unref (G_OBJECT (pixbuf));
pixbuf = new_pixbuf;
}
g_assert (gdk_pixbuf_get_has_alpha (pixbuf));
pixels = gdk_pixbuf_get_pixels (pixbuf);
rowstride = gdk_pixbuf_get_rowstride (pixbuf);
height = gdk_pixbuf_get_height (pixbuf);
@ -2502,8 +2511,9 @@ multiply_alpha (GdkPixbuf *pixbuf,
* then it should be modified to contain "alpha"; if the
* pixbuf contains 0, it should remain 0.
*/
*p = (*p * alpha) / 65025; /* (*p / 255) * (alpha / 255); */
/* ((*p / 255.0) * (alpha / 255.0)) * 255; */
*p = (guchar) (((int) *p * (int) alpha) / (int) 255);
++p; /* skip A */
}
@ -2597,8 +2607,9 @@ scale_and_alpha_pixbuf (GdkPixbuf *src,
if (pixbuf)
pixbuf = multiply_alpha (pixbuf,
ALPHA_TO_UCHAR (alpha));
ALPHA_TO_UCHAR (alpha),
pixbuf == src);
return pixbuf;
}
@ -2672,7 +2683,8 @@ draw_op_as_pixbuf (const MetaDrawOp *op,
widget, width, height);
pixbuf = multiply_alpha (pixbuf,
ALPHA_TO_UCHAR (op->data.gradient.alpha));
ALPHA_TO_UCHAR (op->data.gradient.alpha),
FALSE);
}
break;