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2000-01-05 Owen Taylor <otaylor@redhat.com> * doc/Makefile.am doc/gdk-pixbuf-sections.txt doc/gdk-pixbuf.sgml doc/tmpl/scaling.sgml: Added scaling functions into gtk-doc framework. * gdk-pixbuf/gdk-pixbuf-scale.c: Documentation fixes. * gdk-pixbuf/testpixbuf-scale.c (expose_cb): Simplify a bit. * gdk-pixbuf/pixops/pixops.c (pixops_composite_color): Return immediately if scale_x or scale_y is 0.
162 lines
3.6 KiB
Plaintext
162 lines
3.6 KiB
Plaintext
<!-- ##### SECTION Title ##### -->
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Scaling
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<!-- ##### SECTION Short_Description ##### -->
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Scaling pixbufs and scaling and compositing pixbufs
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<!-- ##### SECTION Long_Description ##### -->
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<para>
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gdk-pixbuf contains functions to scale pixbufs, to scale pixbufs and
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composite against an existing image, and to scale pixbufs and
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composite against a solid color or checkerboard. (Compositing a
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checkerboard is a common way to show an image with an alpha-channel in
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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()
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and gdk_pixbuf_composite_color_simple() which create a
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new pixbuf of a given size, scale an original image to fit,
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and then return the new pixmap.
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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 to
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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 image
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doesn't have an alpha channel, calling gdk_pixbuf_composite_color()
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function has exactly the same effect as calling gdk_pixbuf_scale().
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</para>
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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 (ART_PIX_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 / pixbuf->art_pixbuf->width,
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(double) widget->allocation.height / pixbuf->art_pixbuf->height,
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filter_level, 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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<!-- ##### SECTION See_Also ##### -->
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<para>
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</para>
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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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@filter_level:
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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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@filter_level:
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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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@filter_level:
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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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@filter_level:
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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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@filter_level:
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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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@Returns:
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<!--
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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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--> |