2000-01-06 01:08:10 +00:00
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<!-- ##### SECTION Title ##### -->
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2001-02-12 17:50:13 +00:00
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Scaling
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2000-01-06 01:08:10 +00:00
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<!-- ##### SECTION Short_Description ##### -->
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2001-02-12 17:50:13 +00:00
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Scaling pixbufs and scaling and compositing pixbufs
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2000-01-06 01:08:10 +00:00
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<!-- ##### SECTION Long_Description ##### -->
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<para>
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The &gdk-pixbuf; contains functions to scale pixbufs, to scale
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pixbufs and composite against an existing image, and to scale
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pixbufs and composite against a solid color or checkerboard.
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Compositing a checkerboard is a common way to show an image with
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an alpha channel in image-viewing and editing software.
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</para>
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<para>
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Since the full-featured functions (gdk_pixbuf_scale(),
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gdk_pixbuf_composite(), and gdk_pixbuf_composite_color()) are
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rather complex to use and have many arguments, two simple
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convenience functions are provided, gdk_pixbuf_scale_simple() and
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gdk_pixbuf_composite_color_simple() which create a new pixbuf of a
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given size, scale an original image to fit, and then return the
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2001-12-16 21:09:30 +00:00
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new pixbuf.
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2001-02-12 17:50:13 +00:00
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</para>
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<para>
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The following example demonstrates handling an expose event by
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rendering the appropriate area of a source image (which is scaled
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to fit the widget) onto the widget's window. The source image is
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rendered against a checkerboard, which provides a visual
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representation of the alpha channel if the image has one. If the
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image doesn't have an alpha channel, calling
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gdk_pixbuf_composite_color() function has exactly the same effect
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as calling gdk_pixbuf_scale().
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</para>
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Markup fixes.
* gtk/gtkdialog.c, gtk/gtkrc.c, gtk/gtkwidget.c: Markup fixes.
* gdk-pixbuf-io.c: Markup fixes.
* gdk-pixbuf/tmpl/scaling.sgml, gdk/tmpl/fonts.sgml,
gdk/tmpl/general.sgml, gdk/tmpl/rgb.sgml, gdk/tmpl/visuals.sgml,
gdk/tmpl/windows.sgml, gtk/gtk-docs.sgml, gtk/tmpl/gtkaccellabel.sgml,
gtk/tmpl/gtkcombo.sgml, gtk/tmpl/gtkdialog.sgml,
gtk/tmpl/gtkdrawingarea.sgml, gtk/tmpl/gtkeditable.sgml,
gtk/tmpl/gtkfilesel.sgml, gtk/tmpl/gtkfontseldlg.sgml,
gtk/tmpl/gtkimage.sgml, gtk/tmpl/gtkmain.sgml, gtk/tmpl/gtkmenu.sgml,
gtk/tmpl/gtkmessagedialog.sgml, gtk/tmpl/gtkobject.sgml,
gtk/tmpl/gtkpaned.sgml, gtk/tmpl/gtkradiobutton.sgml,
gtk/tmpl/gtkrc.sgml, gtk/tmpl/gtkscale.sgml, gtk/tmpl/gtksignal.sgml,
gtk/tmpl/gtksocket.sgml, gtk/tmpl/gtkspinbutton.sgml,
gtk/tmpl/gtktogglebutton.sgml, gtk/tmpl/gtksignal.sgml,
gtk/tmpl/gtktooltips.sgml, gtk/tmpl/gtkwindow.sgml,
gdk/tmpl/regions.sgml, gtk/tmpl/gtkfontsel.sgml,
gtk/tmpl/gtkpixmap.sgml, gtk/tmpl/gtkprogress.sgml,
gtk/tmpl/gtkselection.sgml, gtk/tmpl/gtktable.sgml,
gtk/tmpl/gtktipsquery.sgml: Markup fixes (mainly examples).
2001-12-13 19:51:24 +00:00
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<example>
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<title>Handling an expose event.</title>
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<programlisting>
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gboolean
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expose_cb (GtkWidget *widget, GdkEventExpose *event, gpointer data)
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{
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GdkPixbuf *dest;
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gdk_window_set_back_pixmap (widget->window, NULL, FALSE);
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dest = gdk_pixbuf_new (GDK_COLORSPACE_RGB, FALSE, 8, event->area.width, event->area.height);
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gdk_pixbuf_composite_color (pixbuf, dest,
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0, 0, event->area.width, event->area.height,
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-event->area.x, -event->area.y,
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(double) widget->allocation.width / gdk_pixbuf_get_width (pixbuf),
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(double) widget->allocation.height / gdk_pixbuf_get_height (pixbuf),
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GDK_INTERP_BILINEAR, 255,
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event->area.x, event->area.y, 16, 0xaaaaaa, 0x555555);
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gdk_pixbuf_render_to_drawable (dest, widget->window, widget->style->fg_gc[GTK_STATE_NORMAL],
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0, 0, event->area.x, event->area.y,
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event->area.width, event->area.height,
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GDK_RGB_DITHER_NORMAL, event->area.x, event->area.y);
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gdk_pixbuf_unref (dest);
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return TRUE;
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}
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</programlisting>
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Markup fixes.
* gtk/gtkdialog.c, gtk/gtkrc.c, gtk/gtkwidget.c: Markup fixes.
* gdk-pixbuf-io.c: Markup fixes.
* gdk-pixbuf/tmpl/scaling.sgml, gdk/tmpl/fonts.sgml,
gdk/tmpl/general.sgml, gdk/tmpl/rgb.sgml, gdk/tmpl/visuals.sgml,
gdk/tmpl/windows.sgml, gtk/gtk-docs.sgml, gtk/tmpl/gtkaccellabel.sgml,
gtk/tmpl/gtkcombo.sgml, gtk/tmpl/gtkdialog.sgml,
gtk/tmpl/gtkdrawingarea.sgml, gtk/tmpl/gtkeditable.sgml,
gtk/tmpl/gtkfilesel.sgml, gtk/tmpl/gtkfontseldlg.sgml,
gtk/tmpl/gtkimage.sgml, gtk/tmpl/gtkmain.sgml, gtk/tmpl/gtkmenu.sgml,
gtk/tmpl/gtkmessagedialog.sgml, gtk/tmpl/gtkobject.sgml,
gtk/tmpl/gtkpaned.sgml, gtk/tmpl/gtkradiobutton.sgml,
gtk/tmpl/gtkrc.sgml, gtk/tmpl/gtkscale.sgml, gtk/tmpl/gtksignal.sgml,
gtk/tmpl/gtksocket.sgml, gtk/tmpl/gtkspinbutton.sgml,
gtk/tmpl/gtktogglebutton.sgml, gtk/tmpl/gtksignal.sgml,
gtk/tmpl/gtktooltips.sgml, gtk/tmpl/gtkwindow.sgml,
gdk/tmpl/regions.sgml, gtk/tmpl/gtkfontsel.sgml,
gtk/tmpl/gtkpixmap.sgml, gtk/tmpl/gtkprogress.sgml,
gtk/tmpl/gtkselection.sgml, gtk/tmpl/gtktable.sgml,
gtk/tmpl/gtktipsquery.sgml: Markup fixes (mainly examples).
2001-12-13 19:51:24 +00:00
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</example>
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2000-12-12 07:32:32 +00:00
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2000-01-06 01:08:10 +00:00
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<!-- ##### SECTION See_Also ##### -->
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2001-02-12 17:50:13 +00:00
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<para>
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Markup fixes.
* gtk/gtkdialog.c, gtk/gtkrc.c, gtk/gtkwidget.c: Markup fixes.
* gdk-pixbuf-io.c: Markup fixes.
* gdk-pixbuf/tmpl/scaling.sgml, gdk/tmpl/fonts.sgml,
gdk/tmpl/general.sgml, gdk/tmpl/rgb.sgml, gdk/tmpl/visuals.sgml,
gdk/tmpl/windows.sgml, gtk/gtk-docs.sgml, gtk/tmpl/gtkaccellabel.sgml,
gtk/tmpl/gtkcombo.sgml, gtk/tmpl/gtkdialog.sgml,
gtk/tmpl/gtkdrawingarea.sgml, gtk/tmpl/gtkeditable.sgml,
gtk/tmpl/gtkfilesel.sgml, gtk/tmpl/gtkfontseldlg.sgml,
gtk/tmpl/gtkimage.sgml, gtk/tmpl/gtkmain.sgml, gtk/tmpl/gtkmenu.sgml,
gtk/tmpl/gtkmessagedialog.sgml, gtk/tmpl/gtkobject.sgml,
gtk/tmpl/gtkpaned.sgml, gtk/tmpl/gtkradiobutton.sgml,
gtk/tmpl/gtkrc.sgml, gtk/tmpl/gtkscale.sgml, gtk/tmpl/gtksignal.sgml,
gtk/tmpl/gtksocket.sgml, gtk/tmpl/gtkspinbutton.sgml,
gtk/tmpl/gtktogglebutton.sgml, gtk/tmpl/gtksignal.sgml,
gtk/tmpl/gtktooltips.sgml, gtk/tmpl/gtkwindow.sgml,
gdk/tmpl/regions.sgml, gtk/tmpl/gtkfontsel.sgml,
gtk/tmpl/gtkpixmap.sgml, gtk/tmpl/gtkprogress.sgml,
gtk/tmpl/gtkselection.sgml, gtk/tmpl/gtktable.sgml,
gtk/tmpl/gtktipsquery.sgml: Markup fixes (mainly examples).
2001-12-13 19:51:24 +00:00
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<link linkend="gdk-GdkRGB">GdkRGB</link>.
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</para>
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2000-12-12 07:32:32 +00:00
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2000-10-29 08:03:34 +00:00
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<!-- ##### ENUM GdkInterpType ##### -->
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<para>
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This enumeration describes the different interpolation modes that
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can be used with the scaling functions. @GDK_INTERP_NEAREST is
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the fastest scaling method, but has horrible quality when
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scaling down. @GDK_INTERP_BILINEAR is the best choice if you
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aren't sure what to choose, it has a good speed/quality balance.
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<note>
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<para>
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Cubic filtering is missing from the list; hyperbolic
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interpolation is just as fast and results in higher quality.
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</para>
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</note>
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</para>
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@GDK_INTERP_NEAREST: Nearest neighbor sampling; this is the fastest
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and lowest quality mode. Quality is normally unacceptable when scaling
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down, but may be OK when scaling up.
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@GDK_INTERP_TILES: This is an accurate simulation of the PostScript
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image operator without any interpolation enabled. Each pixel is
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rendered as a tiny parallelogram of solid color, the edges of which
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are implemented with antialiasing. It resembles nearest neighbor for
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enlargement, and bilinear for reduction.
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@GDK_INTERP_BILINEAR: Best quality/speed balance; use this mode by
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default. Bilinear interpolation. For enlargement, it is
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equivalent to point-sampling the ideal bilinear-interpolated image.
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For reduction, it is equivalent to laying down small tiles and
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integrating over the coverage area.
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@GDK_INTERP_HYPER: This is the slowest and highest quality
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reconstruction function. It is derived from the hyperbolic filters in
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Wolberg's "Digital Image Warping", and is formally defined as the
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hyperbolic-filter sampling the ideal hyperbolic-filter interpolated
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image (the filter is designed to be idempotent for 1:1 pixel mapping).
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<!-- ##### FUNCTION gdk_pixbuf_scale ##### -->
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<para>
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</para>
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@src:
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@dest:
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@dest_x:
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@dest_y:
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@dest_width:
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@dest_height:
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@offset_x:
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@offset_y:
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@scale_x:
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@scale_y:
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@interp_type:
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<!-- ##### FUNCTION gdk_pixbuf_composite ##### -->
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<para>
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</para>
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@src:
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@dest:
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@dest_x:
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@dest_y:
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@dest_width:
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@dest_height:
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@offset_x:
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@offset_y:
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@scale_x:
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@scale_y:
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@interp_type:
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@overall_alpha:
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<!-- ##### FUNCTION gdk_pixbuf_composite_color ##### -->
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<para>
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</para>
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@src:
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@dest:
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@dest_x:
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@dest_y:
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@dest_width:
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@dest_height:
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@offset_x:
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@offset_y:
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@scale_x:
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@scale_y:
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@interp_type:
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@overall_alpha:
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@check_x:
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@check_y:
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@check_size:
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@color1:
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@color2:
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<!-- ##### FUNCTION gdk_pixbuf_scale_simple ##### -->
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<para>
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</para>
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@src:
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@dest_width:
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@dest_height:
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@interp_type:
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@Returns:
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<!-- ##### FUNCTION gdk_pixbuf_composite_color_simple ##### -->
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<para>
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</para>
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@src:
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@dest_width:
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@dest_height:
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@interp_type:
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@overall_alpha:
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@check_size:
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@color1:
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@color2:
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2001-02-12 17:50:13 +00:00
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@Returns: <!--
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Local variables:
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mode: sgml
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sgml-parent-document: ("../gdk-pixbuf.sgml" "book" "refsect2" "")
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End:
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-->
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