The GdkPixbuf Library | |||
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#include <gdk-pixbuf/gdk-pixbuf.h> void gdk_pixbuf_scale (GdkPixbuf *src, GdkPixbuf *dest, int dest_x, int dest_y, int dest_width, int dest_height, |
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; } |
void gdk_pixbuf_scale (GdkPixbuf *src, GdkPixbuf *dest, int dest_x, int dest_y, int dest_width, int dest_height, |
Transforms the image by source image by scaling by scale_x and scale_y then translating by offset_x and offset_y, then renders the rectangle (dest,dest_y,dest_width,dest_height) of the resulting image onto the destination drawable replacing the previous contents.
src : | a GdkPixbuf |
dest : | the GdkPixbuf into which to render the results |
dest_x : | the left coordinate for region to render |
dest_y : | the top coordinate for region to render |
dest_width : | the width of the region to render |
dest_height : | the height of the region to render |
offset_x : | the offset in the X direction (currently rounded to an integer) |
offset_y : | the offset in the Y direction (currently rounded to an integer) |
scale_x : | the scale factor in the X direction |
scale_y : | the scale factor in the Y direction |
filter_level : | the filter quality for the transformation. |
void gdk_pixbuf_composite (GdkPixbuf *src, GdkPixbuf *dest, int dest_x, int dest_y, int dest_width, int dest_height, |
Transforms the image by source image by scaling by scale_x and scale_y then translating by offset_x and offset_y, then composites the rectangle (dest,dest_y,dest_width,dest_height) of the resulting image onto the destination drawable.
src : | a GdkPixbuf |
dest : | the GdkPixbuf into which to render the results |
dest_x : | the left coordinate for region to render |
dest_y : | the top coordinate for region to render |
dest_width : | the width of the region to render |
dest_height : | the height of the region to render |
offset_x : | the offset in the X direction (currently rounded to an integer) |
offset_y : | the offset in the Y direction (currently rounded to an integer) |
scale_x : | the scale factor in the X direction |
scale_y : | the scale factor in the Y direction |
filter_level : | the filter quality for the transformation. |
overall_alpha : | overall alpha for source image (0..255) |
void gdk_pixbuf_composite_color (GdkPixbuf *src, GdkPixbuf *dest, int dest_x, int dest_y, int dest_width, int dest_height, |
Transforms the image by source image by scaling by scale_x and scale_y then translating by offset_x and offset_y, then composites the rectangle (dest,dest_y,dest_width,dest_height) of the resulting image with a checkboard of the colors color1 and color2 and renders it onto the destination drawable.
src : | a GdkPixbuf |
dest : | the GdkPixbuf into which to render the results |
dest_x : | the left coordinate for region to render |
dest_y : | the top coordinate for region to render |
dest_width : | the width of the region to render |
dest_height : | the height of the region to render |
offset_x : | the offset in the X direction (currently rounded to an integer) |
offset_y : | the offset in the Y direction (currently rounded to an integer) |
scale_x : | the scale factor in the X direction |
scale_y : | the scale factor in the Y direction |
filter_level : | the filter quality for the transformation. |
overall_alpha : | overall alpha for source image (0..255) |
check_x : | the X offset for the checkboard (origin of checkboard is at -check_x, -check_y) |
check_y : | the Y offset for the checkboard |
check_size : | the size of checks in the checkboard (must be a power of two) |
color1 : | the color of check at upper left |
color2 : | the color of the other check |
GdkPixbuf* gdk_pixbuf_scale_simple (GdkPixbuf *src, int dest_width, int dest_height, |
Scale the GdkPixbuf src to dest_width x dest_height and render the result into a new GdkPixbuf.
GdkPixbuf* gdk_pixbuf_composite_color_simple (GdkPixbuf *src, int dest_width, int dest_height, |
Scale the GdkPixbuf src to dest_width x dest_height composite the result with a checkboard of colors color1 and color2 and render the result into a new GdkPixbuf.
src : | a GdkPixbuf |
dest_width : | the width of destination image |
dest_height : | the height of destination image |
filter_level : | the filter quality for the transformation. |
overall_alpha : | overall alpha for source image (0..255) |
check_size : | the size of checks in the checkboard (must be a power of two) |
color1 : | the color of check at upper left |
color2 : | the color of the other check |
Returns : | the new GdkPixbuf |