GDK Reference Manual
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# Images

## Name

Images -- an area for bit-mapped graphics stored on the X Windows client.

## Synopsis

    #include <gdk/gdk.h>

    struct      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 It has now been superceded to a large extent by the much more flexible GdkRGB functions.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

### struct GdkImage

    struct GdkImage
    {
      GObject parent_instance;

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

      GdkColormap  *colormap;

      gpointer windowing_data;
    };

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

GObject `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` |
gpointer `mem` | the pixel data.
GdkColormap *`colormap` |
gpointer `windowing_data` |

### 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.

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GdkRGB | Pixbufs