Images

Images — A client-side area for bit-mapped graphics

Synopsis


#include <gdk/gdk.h>


            GdkImage;
GdkImage*   gdk_image_new                   (GdkImageType type,
                                             GdkVisual *visual,
                                             gint width,
                                             gint height);
enum        GdkImageType;
GdkImage*   gdk_image_new_bitmap            (GdkVisual *visual,
                                             gpointer data,
                                             gint width,
                                             gint height);
GdkImage*   gdk_image_get                   (GdkDrawable *drawable,
                                             gint x,
                                             gint y,
                                             gint width,
                                             gint height);
GdkImage*   gdk_image_ref                   (GdkImage *image);
void        gdk_image_unref                 (GdkImage *image);
#define     gdk_image_destroy
GdkColormap* gdk_image_get_colormap         (GdkImage *image);
void        gdk_image_set_colormap          (GdkImage *image,
                                             GdkColormap *colormap);

void        gdk_image_put_pixel             (GdkImage *image,
                                             gint x,
                                             gint y,
                                             guint32 pixel);
guint32     gdk_image_get_pixel             (GdkImage *image,
                                             gint x,
                                             gint y);

Description

The GdkImage type represents an area for drawing graphics. It has now been superceded to a large extent by the much more flexible GdkRGB functions.

To create an empty GdkImage use gdk_image_new(). To create a GdkImage from bitmap data use gdk_image_new_bitmap(). To create an image from part of a GdkWindow use gdk_drawable_get_image().

The image can be manipulated with gdk_image_get_pixel() and gdk_image_put_pixel(), or alternatively by changing the actual pixel data. Though manipulating the pixel data requires complicated code to cope with the different formats that may be used.

To draw a GdkImage in a GdkWindow or GdkPixmap use gdk_draw_image().

To destroy a GdkImage use gdk_image_destroy().

Details

GdkImage

typedef struct {
  GObject parent_instance;

  
  GdkImageType	type; /* read only. */
  GdkVisual    *visual;	    /* read only. visual used to create the image */
  GdkByteOrder	byte_order; /* read only. */
  gint		width; /* read only. */
  gint		height; /* read only. */
  guint16	depth; /* read only. */
  guint16	bpp;	        /* read only. bytes per pixel */
  guint16	bpl;	        /* read only. bytes per line */
  guint16       bits_per_pixel; /* read only. bits per pixel */
  gpointer	mem;

  GdkColormap  *colormap; /* read only. */
} GdkImage;

The GdkImage struct contains information on the image and the pixel data.

GObject parent_instance; the parent instance
GdkImageType type; the type of the image.
GdkVisual *visual; the visual.
GdkByteOrder byte_order; the byte order.
gint width; the width of the image in pixels.
gint height; the height of the image in pixels.
guint16 depth; the depth of the image, i.e. the number of bits per pixel.
guint16 bpp; the number of bytes per pixel.
guint16 bpl; the number of bytes per line of the image.
guint16 bits_per_pixel; the number of bits per pixel.
gpointer mem; the pixel data.
GdkColormap *colormap; the GdkColormap associated with the image

gdk_image_new ()

GdkImage*   gdk_image_new                   (GdkImageType type,
                                             GdkVisual *visual,
                                             gint width,
                                             gint height);

Creates a new GdkImage.

type : the type of the GdkImage, one of GDK_IMAGE_NORMAL, GDK_IMAGE_SHARED and GDK_IMAGE_FASTEST. GDK_IMAGE_FASTEST is probably the best choice, since it will try creating a GDK_IMAGE_SHARED image first and if that fails it will then use GDK_IMAGE_NORMAL.
visual : the GdkVisual to use for the image.
width : the width of the image in pixels.
height : the height of the image in pixels.
Returns : a new GdkImage, or NULL if the image could not be created.

enum GdkImageType

typedef enum
{
  GDK_IMAGE_NORMAL,
  GDK_IMAGE_SHARED,
  GDK_IMAGE_FASTEST
} GdkImageType;

Specifies the type of a GdkImage.

GDK_IMAGE_NORMAL The original X image type, which is quite slow since the image has to be transferred from the client to the server to display it.
GDK_IMAGE_SHARED A faster image type, which uses shared memory to transfer the image data between client and server. However this will only be available if client and server are on the same machine and the shared memory extension is supported by the server.
GDK_IMAGE_FASTEST Specifies that GDK_IMAGE_SHARED should be tried first, and if that fails then GDK_IMAGE_NORMAL will be used.

gdk_image_new_bitmap ()

GdkImage*   gdk_image_new_bitmap            (GdkVisual *visual,
                                             gpointer data,
                                             gint width,
                                             gint height);

Warning

gdk_image_new_bitmap is deprecated and should not be used in newly-written code.

Creates a new GdkImage with a depth of 1 from the given data.

Warning

THIS FUNCTION IS INCREDIBLY BROKEN. The passed-in data must be allocated by malloc() (NOT g_malloc()) and will be freed when the image is freed.

visual : the GdkVisual to use for the image.
data : the pixel data.
width : the width of the image in pixels.
height : the height of the image in pixels.
Returns : a new GdkImage.

gdk_image_get ()

GdkImage*   gdk_image_get                   (GdkDrawable *drawable,
                                             gint x,
                                             gint y,
                                             gint width,
                                             gint height);

Warning

gdk_image_get is deprecated and should not be used in newly-written code.

This is a deprecated wrapper for gdk_drawable_get_image(); gdk_drawable_get_image() should be used instead. Or even better: in most cases gdk_pixbuf_get_from_drawable() is the most convenient choice.

drawable : a GdkDrawable
x : x coordinate in window
y : y coordinate in window
width : width of area in window
height : height of area in window
Returns : a new GdkImage or NULL

gdk_image_ref ()

GdkImage*   gdk_image_ref                   (GdkImage *image);

Warning

gdk_image_ref is deprecated and should not be used in newly-written code.

Deprecated function; use g_object_ref() instead.

image : a GdkImage
Returns : the image

gdk_image_unref ()

void        gdk_image_unref                 (GdkImage *image);

Warning

gdk_image_unref is deprecated and should not be used in newly-written code.

Deprecated function; use g_object_unref() instead.

image : a GdkImage

gdk_image_destroy

#define gdk_image_destroy              gdk_image_unref

Warning

gdk_image_destroy is deprecated and should not be used in newly-written code.

Destroys a GdkImage, freeing any resources allocated for it.

gdk_image_get_colormap ()

GdkColormap* gdk_image_get_colormap         (GdkImage *image);

Retrieves the colormap for a given image, if it exists. An image will have a colormap if the drawable from which it was created has a colormap, or if a colormap was set explicitely with gdk_image_set_colormap().

image : a GdkImage
Returns : colormap for the image

gdk_image_set_colormap ()

void        gdk_image_set_colormap          (GdkImage *image,
                                             GdkColormap *colormap);

Sets the colormap for the image to the given colormap. Normally there's no need to use this function, images are created with the correct colormap if you get the image from a drawable. If you create the image from scratch, use the colormap of the drawable you intend to render the image to.

image : a GdkImage
colormap : a GdkColormap

gdk_image_put_pixel ()

void        gdk_image_put_pixel             (GdkImage *image,
                                             gint x,
                                             gint y,
                                             guint32 pixel);

Sets a pixel in a GdkImage to a given pixel value.

image : a GdkImage.
x : the x coordinate of the pixel to set.
y : the y coordinate of the pixel to set.
pixel : the pixel value to set.

gdk_image_get_pixel ()

guint32     gdk_image_get_pixel             (GdkImage *image,
                                             gint x,
                                             gint y);

Gets a pixel value at a specified position in a GdkImage.

image : a GdkImage.
x : the x coordinate of the pixel to get.
y : the y coordinate of the pixel to get.
Returns : the pixel value at the given position.

See Also

Bitmaps and Pixmaps

Graphics which are stored on the X Windows server. Since these are stored on the server they can be drawn very quickly, and all of the Drawing Primitives can be used to draw on them. Their main disadvantage is that manipulating individual pixels can be very slow.

GdkRGB

Built on top of GdkImage, this provides much more functionality, including the dithering of colors to produce better output on low-color displays.