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 Scaling and compositing functions take advantage of MMX hardware
28 acceleration on systems where MMX is supported. If gdk-pixbuf is built
29 with the Sun mediaLib library, these functions are instead accelerated
30 using mediaLib, which provides hardware acceleration on Intel, AMD,
31 and Sparc chipsets. If desired, mediaLib support can be turned off by
32 setting the GDK_DISABLE_MEDIALIB environment variable.
36 The following example demonstrates handling an expose event by
37 rendering the appropriate area of a source image (which is scaled
38 to fit the widget) onto the widget's window. The source image is
39 rendered against a checkerboard, which provides a visual
40 representation of the alpha channel if the image has one. If the
41 image doesn't have an alpha channel, calling
42 gdk_pixbuf_composite_color() function has exactly the same effect
43 as calling gdk_pixbuf_scale().
47 <title>Handling an expose event.</title>
50 expose_cb (GtkWidget *widget, GdkEventExpose *event, gpointer data)
54 dest = gdk_pixbuf_new (GDK_COLORSPACE_RGB, FALSE, 8, event->area.width, event->area.height);
56 gdk_pixbuf_composite_color (pixbuf, dest,
57 0, 0, event->area.width, event->area.height,
58 -event->area.x, -event->area.y,
59 (double) widget->allocation.width / gdk_pixbuf_get_width (pixbuf),
60 (double) widget->allocation.height / gdk_pixbuf_get_height (pixbuf),
61 GDK_INTERP_BILINEAR, 255,
62 event->area.x, event->area.y, 16, 0xaaaaaa, 0x555555);
64 gdk_draw_pixbuf (widget->window, widget->style->fg_gc[GTK_STATE_NORMAL], dest,
65 0, 0, event->area.x, event->area.y,
66 event->area.width, event->area.height,
67 GDK_RGB_DITHER_NORMAL, event->area.x, event->area.y);
69 gdk_pixbuf_unref (dest);
76 <!-- ##### SECTION See_Also ##### -->
78 <link linkend="gdk-GdkRGB">GdkRGB</link>.
81 <!-- ##### SECTION Stability_Level ##### -->
84 <!-- ##### ENUM GdkInterpType ##### -->
86 This enumeration describes the different interpolation modes that
87 can be used with the scaling functions. @GDK_INTERP_NEAREST is
88 the fastest scaling method, but has horrible quality when
89 scaling down. @GDK_INTERP_BILINEAR is the best choice if you
90 aren't sure what to choose, it has a good speed/quality balance.
94 Cubic filtering is missing from the list; hyperbolic
95 interpolation is just as fast and results in higher quality.
100 @GDK_INTERP_NEAREST: Nearest neighbor sampling; this is the fastest
101 and lowest quality mode. Quality is normally unacceptable when scaling
102 down, but may be OK when scaling up.
103 @GDK_INTERP_TILES: This is an accurate simulation of the PostScript
104 image operator without any interpolation enabled. Each pixel is
105 rendered as a tiny parallelogram of solid color, the edges of which
106 are implemented with antialiasing. It resembles nearest neighbor for
107 enlargement, and bilinear for reduction.
108 @GDK_INTERP_BILINEAR: Best quality/speed balance; use this mode by
109 default. Bilinear interpolation. For enlargement, it is
110 equivalent to point-sampling the ideal bilinear-interpolated image.
111 For reduction, it is equivalent to laying down small tiles and
112 integrating over the coverage area.
113 @GDK_INTERP_HYPER: This is the slowest and highest quality
114 reconstruction function. It is derived from the hyperbolic filters in
115 Wolberg's "Digital Image Warping", and is formally defined as the
116 hyperbolic-filter sampling the ideal hyperbolic-filter interpolated
117 image (the filter is designed to be idempotent for 1:1 pixel mapping).
119 <!-- ##### FUNCTION gdk_pixbuf_scale_simple ##### -->
131 <!-- ##### FUNCTION gdk_pixbuf_scale ##### -->
149 <!-- ##### FUNCTION gdk_pixbuf_composite_color_simple ##### -->
165 sgml-parent-document: ("../gdk-pixbuf.sgml" "book" "refsect2" "")
170 <!-- ##### FUNCTION gdk_pixbuf_composite ##### -->
189 <!-- ##### FUNCTION gdk_pixbuf_composite_color ##### -->
213 <!-- ##### ENUM GdkPixbufRotation ##### -->
215 The possible rotations which can be passed to gdk_pixbuf_rotate_simple().
216 To make them easier to use, their numerical values are the actual degrees.
219 @GDK_PIXBUF_ROTATE_NONE: No rotation.
220 @GDK_PIXBUF_ROTATE_COUNTERCLOCKWISE: Rotate by 90 degrees.
221 @GDK_PIXBUF_ROTATE_UPSIDEDOWN: Rotate by 180 degrees.
222 @GDK_PIXBUF_ROTATE_CLOCKWISE: Rotate by 270 degrees.
224 <!-- ##### FUNCTION gdk_pixbuf_rotate_simple ##### -->
234 <!-- ##### FUNCTION gdk_pixbuf_flip ##### -->