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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.
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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> 2002-04-05 Havoc Pennington <hp@pobox.com>
* src/stack.c: remove the unused tab stuff * src/stack.c: remove the unused tab stuff

20
src/theme.c
View File

@ -2460,7 +2460,8 @@ get_gc_for_primitive (GtkWidget *widget,
static GdkPixbuf* static GdkPixbuf*
multiply_alpha (GdkPixbuf *pixbuf, multiply_alpha (GdkPixbuf *pixbuf,
guchar alpha) guchar alpha,
gboolean force_copy)
{ {
GdkPixbuf *new_pixbuf; GdkPixbuf *new_pixbuf;
guchar *pixels; guchar *pixels;
@ -2479,6 +2480,14 @@ multiply_alpha (GdkPixbuf *pixbuf,
g_object_unref (G_OBJECT (pixbuf)); g_object_unref (G_OBJECT (pixbuf));
pixbuf = new_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); pixels = gdk_pixbuf_get_pixels (pixbuf);
rowstride = gdk_pixbuf_get_rowstride (pixbuf); rowstride = gdk_pixbuf_get_rowstride (pixbuf);
@ -2502,7 +2511,8 @@ multiply_alpha (GdkPixbuf *pixbuf,
* then it should be modified to contain "alpha"; if the * then it should be modified to contain "alpha"; if the
* pixbuf contains 0, it should remain 0. * 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 */ ++p; /* skip A */
} }
@ -2597,7 +2607,8 @@ scale_and_alpha_pixbuf (GdkPixbuf *src,
if (pixbuf) if (pixbuf)
pixbuf = multiply_alpha (pixbuf, pixbuf = multiply_alpha (pixbuf,
ALPHA_TO_UCHAR (alpha)); ALPHA_TO_UCHAR (alpha),
pixbuf == src);
return pixbuf; return pixbuf;
} }
@ -2672,7 +2683,8 @@ draw_op_as_pixbuf (const MetaDrawOp *op,
widget, width, height); widget, width, height);
pixbuf = multiply_alpha (pixbuf, pixbuf = multiply_alpha (pixbuf,
ALPHA_TO_UCHAR (op->data.gradient.alpha)); ALPHA_TO_UCHAR (op->data.gradient.alpha),
FALSE);
} }
break; break;