1 <!-- ##### SECTION Title ##### -->
4 <!-- ##### SECTION Short_Description ##### -->
5 Scaling pixbufs and scaling and compositing pixbufs
7 <!-- ##### SECTION Long_Description ##### -->
9 The &gdk-pixbuf; contains functions to scale pixbufs, to scale
10 pixbufs and composite against an existing image, and to scale
11 pixbufs and composite against a solid color or checkerboard.
12 Compositing a checkerboard is a common way to show an image with
13 an alpha channel in image-viewing and editing software.
17 Since the full-featured functions (gdk_pixbuf_scale(),
18 gdk_pixbuf_composite(), and gdk_pixbuf_composite_color()) are
19 rather complex to use and have many arguments, two simple
20 convenience functions are provided, gdk_pixbuf_scale_simple() and
21 gdk_pixbuf_composite_color_simple() which create a new pixbuf of a
22 given size, scale an original image to fit, and then return the
27 The following example demonstrates handling an expose event by
28 rendering the appropriate area of a source image (which is scaled
29 to fit the widget) onto the widget's window. The source image is
30 rendered against a checkerboard, which provides a visual
31 representation of the alpha channel if the image has one. If the
32 image doesn't have an alpha channel, calling
33 gdk_pixbuf_composite_color() function has exactly the same effect
34 as calling gdk_pixbuf_scale().
38 <title>Handling an expose event.</title>
41 expose_cb (GtkWidget *widget, GdkEventExpose *event, gpointer data)
45 gdk_window_set_back_pixmap (widget->window, NULL, FALSE);
47 dest = gdk_pixbuf_new (GDK_COLORSPACE_RGB, FALSE, 8, event->area.width, event->area.height);
49 gdk_pixbuf_composite_color (pixbuf, dest,
50 0, 0, event->area.width, event->area.height,
51 -event->area.x, -event->area.y,
52 (double) widget->allocation.width / gdk_pixbuf_get_width (pixbuf),
53 (double) widget->allocation.height / gdk_pixbuf_get_height (pixbuf),
54 GDK_INTERP_BILINEAR, 255,
55 event->area.x, event->area.y, 16, 0xaaaaaa, 0x555555);
57 gdk_pixbuf_render_to_drawable (dest, widget->window, widget->style->fg_gc[GTK_STATE_NORMAL],
58 0, 0, event->area.x, event->area.y,
59 event->area.width, event->area.height,
60 GDK_RGB_DITHER_NORMAL, event->area.x, event->area.y);
62 gdk_pixbuf_unref (dest);
69 <!-- ##### SECTION See_Also ##### -->
71 <link linkend="gdk-GdkRGB">GdkRGB</link>.
74 <!-- ##### SECTION Stability_Level ##### -->
77 <!-- ##### ENUM GdkInterpType ##### -->
79 This enumeration describes the different interpolation modes that
80 can be used with the scaling functions. @GDK_INTERP_NEAREST is
81 the fastest scaling method, but has horrible quality when
82 scaling down. @GDK_INTERP_BILINEAR is the best choice if you
83 aren't sure what to choose, it has a good speed/quality balance.
87 Cubic filtering is missing from the list; hyperbolic
88 interpolation is just as fast and results in higher quality.
93 @GDK_INTERP_NEAREST: Nearest neighbor sampling; this is the fastest
94 and lowest quality mode. Quality is normally unacceptable when scaling
95 down, but may be OK when scaling up.
96 @GDK_INTERP_TILES: This is an accurate simulation of the PostScript
97 image operator without any interpolation enabled. Each pixel is
98 rendered as a tiny parallelogram of solid color, the edges of which
99 are implemented with antialiasing. It resembles nearest neighbor for
100 enlargement, and bilinear for reduction.
101 @GDK_INTERP_BILINEAR: Best quality/speed balance; use this mode by
102 default. Bilinear interpolation. For enlargement, it is
103 equivalent to point-sampling the ideal bilinear-interpolated image.
104 For reduction, it is equivalent to laying down small tiles and
105 integrating over the coverage area.
106 @GDK_INTERP_HYPER: This is the slowest and highest quality
107 reconstruction function. It is derived from the hyperbolic filters in
108 Wolberg's "Digital Image Warping", and is formally defined as the
109 hyperbolic-filter sampling the ideal hyperbolic-filter interpolated
110 image (the filter is designed to be idempotent for 1:1 pixel mapping).
112 <!-- ##### FUNCTION gdk_pixbuf_scale_simple ##### -->
124 <!-- ##### FUNCTION gdk_pixbuf_scale ##### -->
142 <!-- ##### FUNCTION gdk_pixbuf_composite_color_simple ##### -->
158 sgml-parent-document: ("../gdk-pixbuf.sgml" "book" "refsect2" "")
163 <!-- ##### FUNCTION gdk_pixbuf_composite ##### -->
182 <!-- ##### FUNCTION gdk_pixbuf_composite_color ##### -->
206 <!-- ##### ENUM GdkPixbufRotation ##### -->
208 The possible rotations which can be passed to gdk_pixbuf_rotate_simple().
209 To make them easier to use, their numerical values are the actual degrees.
212 @GDK_PIXBUF_ROTATE_NONE: No rotation.
213 @GDK_PIXBUF_ROTATE_COUNTERCLOCKWISE: Rotate by 90 degrees.
214 @GDK_PIXBUF_ROTATE_UPSIDEDOWN: Rotate by 180 degrees.
215 @GDK_PIXBUF_ROTATE_CLOCKWISE: Rotate by 270 degrees.
217 <!-- ##### FUNCTION gdk_pixbuf_rotate_simple ##### -->
227 <!-- ##### FUNCTION gdk_pixbuf_flip ##### -->