Re: GdkPixbuf change brightness [was:(no subject)]

[Iago Rubio <iago rubio hispalinux es>]

On Wed, 2005-01-12 at 07:24, anne isac wrote:
> On Mon, 10 Jan 2005 17:27:09 +0100 Iago Rubio wrote: 
>
> > You can change the brightness in a GdkPixbuf in various ways. 
> > One convenient could be a call to 
> > gdk_pixbuf_saturate_and_pixelate(). 

> I tried using gdk_pixbuf_saturate_and_pixelate() it does work but now
> the issue is,
>
>  gdk_pixbuf_saturate_and_pixelate() takes a sorce Pixbuf and a
> Destination PixBuf   and if i do
>
> GtkPixBuf *destPixBuf;
> gdk_pixbuf_saturate_and_pixelate(srcPixbuf,destPixBuf,brightness,FALSE)
>
> I get a Gtk-CRITICAL message...
>
> Gtk-CRITICAL **: file gtkwidget.c: line 4240 (gtk_widget_set_parent):
> assertion `widget->parent == NULL' failed
> (try:26788): GdkPixbuf-CRITICAL **: file gdk-pixbuf-util.c: line 180
> (gdk_pixbuf_saturate_and_pixelate): assertion `GDK_IS_PIXBUF (dest)'
> failed

gdk_pixbuf_saturate_and_pixelate expects a GdkPixbuf object not a
placeholder for the return value.

May be you could try:

GtkPixBuf *destPixBuf = gtk_pixbuff_new(
        gdk_pixbuf_get_colorspace (srcPixbuf),
        gdk_pixbuf_get_has_alpha (srcPixbuf),
        gdk_pixbuf_get_bits_per_sample (srcPixbuf),
        gdk_pixbuf_get_width (srcPixbuf),
        gdk_pixbuf_get_height (srcPixbuf)
);

gdk_pixbuf_saturate_and_pixelate(srcPixbuf,destPixBuf,brightness,FALSE);

This way you'll got a properly built pixbuf, as placeholder for the
returned value.

> and if i assign destPixBuf=srcPixBuf
>
> then every time i have a new source buffer which is not what is
> wanted.
>
> how do i copy the contents of the source buffer to the destination
> buffer before i call gdk_pixbuf_saturate_and_pixelate();

destPixBuf = gdk_pixbuf_copy (srcPixbuf);

if(destPixBuf)
{
        // do something useful
}
else
{
        // warn, not enought memory
}

> or is there another way to avoid the Gtk-CRITICAL condition???

You should pass a properly built pixbuf to
gdk_pixbuf_saturate_and_pixelate.

It could be a new one, a copy of the source pixbuf, or the same pixbuf
as source and destination, if you don't care to loose the source one.

> Please Help

I hope it helps.

> Thanking you in anticipation

You're welcome.
-- 
Iago Rubio