Re: Bitmap transparency

[xapantu <xapantu gmail com>]

Hi,

Any chance for another release for the 0.x serie ? We need it for gtk2,
we won't use gtk3 until the summer :)

And, if no, can we release a patched version in our ppa ?
(ppa:ella-animation/dev)

I have just managed to start making the patch, it is quite small. It
isn't finished, I need to update the documentation (and the examples),
and it is for goocanvas-0.15. I am going to install gtk3 tomorrow to
test with the master branch but I think it should work.

--xapantu

--- ../../goocanvas-0.15/src/goocanvasimage.c	2009-06-29
15:10:09.000000000 +0200
+++ src/goocanvasimage.c	2010-12-08 21:20:46.289732403 +0100
@@ -53,6 +53,7 @@
   PROP_WIDTH,
   PROP_HEIGHT,
   PROP_SCALE_TO_FIT,
+  PROP_ALPHA,
 
   /* Convenience properties. */
   PROP_PIXBUF
@@ -116,6 +117,7 @@
 							0.0, G_MAXDOUBLE, 0.0,
 							G_PARAM_READWRITE));
 
+
   g_object_class_install_property (gobject_class, PROP_SCALE_TO_FIT, 
                                    g_param_spec_boolean
("scale-to-fit",
 							 _("Scale To Fit"),
@@ -123,12 +125,20 @@
 							 FALSE,
 							 G_PARAM_READWRITE));
 
+  g_object_class_install_property (gobject_class, PROP_ALPHA,
+				   g_param_spec_double ("alpha",
+							_("Alpha"),
+							_("The opacity of the image"),
+							0.0, G_MAXDOUBLE, 0.0,
+							G_PARAM_READWRITE));
+
   g_object_class_install_property (gobject_class, PROP_PIXBUF,
 				   g_param_spec_object ("pixbuf",
 							_("Pixbuf"),
 							_("The GdkPixbuf to display"),
 							GDK_TYPE_PIXBUF,
 							G_PARAM_WRITABLE));
+
 }
 
 
@@ -335,6 +345,9 @@
     case PROP_WIDTH:
       image_data->width = g_value_get_double (value);
       break;
+    case PROP_ALPHA:
+      image_data->alpha = g_value_get_double (value);
+      break;
     case PROP_HEIGHT:
       image_data->height = g_value_get_double (value);
       break;
@@ -421,6 +434,7 @@
   cairo_surface_t *surface;
   gdouble width, height;
 
+ //cairo_paint_with_alpha(cr, 0.1);
   if (!image_data->pattern)
     return;
 
@@ -445,7 +459,10 @@
   cairo_set_source (cr, image_data->pattern);
   cairo_rectangle (cr, image_data->x, image_data->y,
 		   image_data->width, image_data->height);
-  cairo_fill (cr);
+  if(image_data->alpha != 1.0)
+      cairo_paint_with_alpha (cr, image_data->alpha);
+  else
+    cairo_fill (cr);
 #else
   /* Using cairo_paint() used to be much slower than cairo_fill(),
though
      they seem similar now. I'm not sure if it matters which we use. */


Le mardi 07 décembre 2010 à 22:33 +0000, Damon Chaplin a écrit :
> On Tue, 2010-12-07 at 19:17 +0100, xapantu wrote:
> > Hi,
> > 
> > I would like to know if I could set a custom opacity value for bitmap ?
> > I can't find it in the api reference...
> > 
> > And if it is not (yet) implemented, maybe I can do a patch ? You agree
> > to include it in a next version of GooCanvas ? (because I don't want to
> > ask to the user to patch GooCanvas ^^).
> > 
> > I am a developer of Ella (http://ella.tuxfamily.org) and we really need
> > this feature ^^.
> 
> No, I don't think there is a way to set the opacity of a bitmap at
> present. I guess you could use cairo_paint_with_alpha() to do that.
> 
> A patch would be welcome, as long as it isn't too complicated.
> 
> Or you could write your own custom item.
> 
> 
> > Thanks for all your work, GooCanvas is definitively awesome!
> 
> Thanks,
> 
> Damon
> 
>