gtk2/docs/reference/gdk-pixbuf/tmpl/scaling.sgml

<!-- ##### SECTION Title ##### -->
Scaling

<!-- ##### SECTION Short_Description ##### -->
Scaling pixbufs and scaling and compositing pixbufs

<!-- ##### SECTION Long_Description ##### -->
<para>
gdk-pixbuf contains functions to scale pixbufs, to scale pixbufs and
composite against an existing image, and to scale pixbufs and
composite against a solid color or checkerboard.  (Compositing a
checkerboard is a common way to show an image with an alpha-channel in
image-viewing and editing software.)
</para>
<para>
Since the full-featured functions (gdk_pixbuf_scale(),
gdk_pixbuf_composite(), and gdk_pixbuf_composite_color()) are
rather complex to use and have many arguments, two simple
convenience functions are provided, gdk_pixbuf_scale_simple()
and gdk_pixbuf_composite_color_simple() which create a
new pixbuf of a given size, scale an original image to fit,
and then return the new pixmap.
</para>

<para>
The following example demonstrates handling an expose event by
rendering the appropriate area of a source image (which is scaled to
fit the widget) onto the widget's window.  The source image is
rendered against a checkerboard, which provides a visual
representation of the alpha channel if the image has one. If the image
doesn't have an alpha channel, calling gdk_pixbuf_composite_color()
function has exactly the same effect as calling gdk_pixbuf_scale().
</para>

<programlisting>
gboolean
expose_cb (GtkWidget *widget, GdkEventExpose *event, gpointer data)
{
  GdkPixbuf *dest;

  gdk_window_set_back_pixmap (widget->window, NULL, FALSE);
  
  dest = gdk_pixbuf_new (ART_PIX_RGB, FALSE, 8, event->area.width, event->area.height);

  gdk_pixbuf_composite_color (pixbuf, dest,
                              0, 0, event->area.width, event->area.height,
                              -event->area.x, -event->area.y,
                              (double) widget->allocation.width / pixbuf->art_pixbuf->width,
                              (double) widget->allocation.height / pixbuf->art_pixbuf->height,
                              filter_level, 255,
                               event->area.x, event->area.y, 16, 0xaaaaaa, 0x555555);

  gdk_pixbuf_render_to_drawable (dest, widget->window, widget->style->fg_gc[GTK_STATE_NORMAL],
                                 0, 0, event->area.x, event->area.y,
                                 event->area.width, event->area.height,
                                 GDK_RGB_DITHER_NORMAL, event->area.x, event->area.y);
  
  gdk_pixbuf_unref (dest);
  
  return TRUE;
}
</programlisting>

<!-- ##### SECTION See_Also ##### -->
<para>

</para>

<!-- ##### FUNCTION gdk_pixbuf_scale ##### -->
<para>

</para>

@src: 
@dest: 
@dest_x: 
@dest_y: 
@dest_width: 
@dest_height: 
@offset_x: 
@offset_y: 
@scale_x: 
@scale_y: 
@filter_level: 


<!-- ##### FUNCTION gdk_pixbuf_composite ##### -->
<para>

</para>

@src: 
@dest: 
@dest_x: 
@dest_y: 
@dest_width: 
@dest_height: 
@offset_x: 
@offset_y: 
@scale_x: 
@scale_y: 
@filter_level: 
@overall_alpha: 


<!-- ##### FUNCTION gdk_pixbuf_composite_color ##### -->
<para>

</para>

@src: 
@dest: 
@dest_x: 
@dest_y: 
@dest_width: 
@dest_height: 
@offset_x: 
@offset_y: 
@scale_x: 
@scale_y: 
@filter_level: 
@overall_alpha: 
@check_x: 
@check_y: 
@check_size: 
@color1: 
@color2: 


<!-- ##### FUNCTION gdk_pixbuf_scale_simple ##### -->
<para>

</para>

@src: 
@dest_width: 
@dest_height: 
@filter_level: 
@Returns: 


<!-- ##### FUNCTION gdk_pixbuf_composite_color_simple ##### -->
<para>

</para>

@src: 
@dest_width: 
@dest_height: 
@filter_level: 
@overall_alpha: 
@check_size: 
@color1: 
@color2: 
@Returns: <!--
Local variables:
mode: sgml
sgml-parent-document: ("../gdk-pixbuf.sgml" "book" "refsect2" "")
End:
-->