Scaling
Scaling pixbufs and scaling and compositing pixbufs
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.)
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.
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().
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;
}
@src:
@dest:
@dest_x:
@dest_y:
@dest_width:
@dest_height:
@offset_x:
@offset_y:
@scale_x:
@scale_y:
@filter_level:
@src:
@dest:
@dest_x:
@dest_y:
@dest_width:
@dest_height:
@offset_x:
@offset_y:
@scale_x:
@scale_y:
@filter_level:
@overall_alpha:
@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:
@src:
@dest_width:
@dest_height:
@filter_level:
@Returns:
@src:
@dest_width:
@dest_height:
@filter_level:
@overall_alpha:
@check_size:
@color1:
@color2:
@Returns: