The GdkPixbuf Structure

The GdkPixbuf Structure — Information that describes an image.

Properties

gint bits-per-sample Read / Write / Construct Only
GdkColorspace colorspace Read / Write / Construct Only
gboolean has-alpha Read / Write / Construct Only
gint height Read / Write / Construct Only
gint n-channels Read / Write / Construct Only
GBytes * pixel-bytes Read / Write / Construct Only
gpointer pixels Read / Write / Construct Only
gint rowstride Read / Write / Construct Only
gint width Read / Write / Construct Only

Types and Values

Object Hierarchy

    GObject
    ╰── GdkPixbuf

Implemented Interfaces

GdkPixbuf implements GIcon and GLoadableIcon.

Includes

#include <gdk-pixbuf/gdk-pixbuf.h>

Description

The GdkPixbuf structure contains information that describes an image in memory.

Image Data

Image data in a pixbuf is stored in memory in uncompressed, packed format. Rows in the image are stored top to bottom, and in each row pixels are stored from left to right. There may be padding at the end of a row. The "rowstride" value of a pixbuf, as returned by gdk_pixbuf_get_rowstride(), indicates the number of bytes between rows.

put_pixel() Example

The following code illustrates a simple put_pixel() function for RGB pixbufs with 8 bits per channel with an alpha channel. It is not included in the gdk-pixbuf library for performance reasons; rather than making several function calls for each pixel, your own code can take shortcuts.

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static void
put_pixel (GdkPixbuf *pixbuf, int x, int y, guchar red, guchar green, guchar blue, guchar alpha)
{
  int width, height, rowstride, n_channels;
  guchar *pixels, *p;

  n_channels = gdk_pixbuf_get_n_channels (pixbuf);

  g_assert (gdk_pixbuf_get_colorspace (pixbuf) == GDK_COLORSPACE_RGB);
  g_assert (gdk_pixbuf_get_bits_per_sample (pixbuf) == 8);
  g_assert (gdk_pixbuf_get_has_alpha (pixbuf));
  g_assert (n_channels == 4);

  width = gdk_pixbuf_get_width (pixbuf);
  height = gdk_pixbuf_get_height (pixbuf);

  g_assert (x >= 0 && x < width);
  g_assert (y >= 0 && y < height);

  rowstride = gdk_pixbuf_get_rowstride (pixbuf);
  pixels = gdk_pixbuf_get_pixels (pixbuf);

  p = pixels + y * rowstride + x * n_channels;
  p[0] = red;
  p[1] = green;
  p[2] = blue;
  p[3] = alpha;
}

This function will not work for pixbufs with images that are other than 8 bits per sample or channel, but it will work for most of the pixbufs that GTK+ uses.

If you are doing memcpy() of raw pixbuf data, note that the last row in the pixbuf may not be as wide as the full rowstride, but rather just as wide as the pixel data needs to be. That is, it is unsafe to do memcpy (dest, pixels, rowstride * height) to copy a whole pixbuf. Use gdk_pixbuf_copy() instead, or compute the width in bytes of the last row as width * ((n_channels * bits_per_sample + 7) / 8).

Functions

gdk_pixbuf_get_colorspace ()

GdkColorspace
gdk_pixbuf_get_colorspace (const GdkPixbuf *pixbuf);

Queries the color space of a pixbuf.

Parameters

pixbuf

A pixbuf.

 

Returns

Color space.


gdk_pixbuf_get_n_channels ()

int
gdk_pixbuf_get_n_channels (const GdkPixbuf *pixbuf);

Queries the number of channels of a pixbuf.

Parameters

pixbuf

A pixbuf.

 

Returns

Number of channels.


gdk_pixbuf_get_has_alpha ()

gboolean
gdk_pixbuf_get_has_alpha (const GdkPixbuf *pixbuf);

Queries whether a pixbuf has an alpha channel (opacity information).

Parameters

pixbuf

A pixbuf.

 

Returns

TRUE if it has an alpha channel, FALSE otherwise.


gdk_pixbuf_get_bits_per_sample ()

int
gdk_pixbuf_get_bits_per_sample (const GdkPixbuf *pixbuf);

Queries the number of bits per color sample in a pixbuf.

Parameters

pixbuf

A pixbuf.

 

Returns

Number of bits per color sample.


gdk_pixbuf_get_pixels ()

guchar *
gdk_pixbuf_get_pixels (const GdkPixbuf *pixbuf);

Queries a pointer to the pixel data of a pixbuf.

Parameters

pixbuf

A pixbuf.

 

Returns

A pointer to the pixbuf's pixel data. Please see the section on image data for information about how the pixel data is stored in memory.

This function will cause an implicit copy of the pixbuf data if the pixbuf was created from read-only data.

[array]


gdk_pixbuf_get_pixels_with_length ()

guchar *
gdk_pixbuf_get_pixels_with_length (const GdkPixbuf *pixbuf,
                                   guint *length);

Queries a pointer to the pixel data of a pixbuf.

[rename-to gdk_pixbuf_get_pixels]

Parameters

pixbuf

A pixbuf.

 

length

The length of the binary data.

[out]

Returns

A pointer to the pixbuf's pixel data. Please see the section on image data for information about how the pixel data is stored in memory.

This function will cause an implicit copy of the pixbuf data if the pixbuf was created from read-only data.

[array length=length]

Since: 2.26


gdk_pixbuf_get_width ()

int
gdk_pixbuf_get_width (const GdkPixbuf *pixbuf);

Queries the width of a pixbuf.

Parameters

pixbuf

A pixbuf.

 

Returns

Width in pixels.


gdk_pixbuf_get_height ()

int
gdk_pixbuf_get_height (const GdkPixbuf *pixbuf);

Queries the height of a pixbuf.

Parameters

pixbuf

A pixbuf.

 

Returns

Height in pixels.


gdk_pixbuf_get_rowstride ()

int
gdk_pixbuf_get_rowstride (const GdkPixbuf *pixbuf);

Queries the rowstride of a pixbuf, which is the number of bytes between the start of a row and the start of the next row.

Parameters

pixbuf

A pixbuf.

 

Returns

Distance between row starts.


gdk_pixbuf_get_byte_length ()

gsize
gdk_pixbuf_get_byte_length (const GdkPixbuf *pixbuf);

Returns the length of the pixel data, in bytes.

Parameters

pixbuf

A pixbuf

 

Returns

The length of the pixel data.

Since: 2.26


gdk_pixbuf_get_option ()

const gchar *
gdk_pixbuf_get_option (GdkPixbuf *pixbuf,
                       const gchar *key);

Looks up key in the list of options that may have been attached to the pixbuf when it was loaded, or that may have been attached by another function using gdk_pixbuf_set_option().

For instance, the ANI loader provides "Title" and "Artist" options. The ICO, XBM, and XPM loaders provide "x_hot" and "y_hot" hot-spot options for cursor definitions. The PNG loader provides the tEXt ancillary chunk key/value pairs as options. Since 2.12, the TIFF and JPEG loaders return an "orientation" option string that corresponds to the embedded TIFF/Exif orientation tag (if present). Since 2.32, the TIFF loader sets the "multipage" option string to "yes" when a multi-page TIFF is loaded. Since 2.32 the JPEG and PNG loaders set "x-dpi" and "y-dpi" if the file contains image density information in dots per inch.

Parameters

pixbuf

a GdkPixbuf

 

key

a nul-terminated string.

 

Returns

the value associated with key . This is a nul-terminated string that should not be freed or NULL if key was not found.


gdk_pixbuf_set_option ()

gboolean
gdk_pixbuf_set_option (GdkPixbuf *pixbuf,
                       const gchar *key,
                       const gchar *value);

Attaches a key/value pair as an option to a GdkPixbuf. If key already exists in the list of options attached to pixbuf , the new value is ignored and FALSE is returned.

Parameters

pixbuf

a GdkPixbuf

 

key

a nul-terminated string.

 

value

a nul-terminated string.

 

Returns

TRUE on success.

Since: 2.2


gdk_pixbuf_get_options ()

GHashTable *
gdk_pixbuf_get_options (GdkPixbuf *pixbuf);

Returns a GHashTable with a list of all the options that may have been attached to the pixbuf when it was loaded, or that may have been attached by another function using gdk_pixbuf_set_option().

See gdk_pixbuf_get_option() for more details.

Parameters

pixbuf

a GdkPixbuf

 

Returns

a GHashTable of key/values.

[transfer container][element-type utf8 utf8]

Since: 2.32


gdk_pixbuf_read_pixels ()

const guint8 *
gdk_pixbuf_read_pixels (const GdkPixbuf *pixbuf);

Returns a read-only pointer to the raw pixel data; must not be modified. This function allows skipping the implicit copy that must be made if gdk_pixbuf_get_pixels() is called on a read-only pixbuf.

Parameters

pixbuf

A pixbuf

 

Since: 2.32

Types and Values

enum GdkPixbufError

An error code in the GDK_PIXBUF_ERROR domain. Many gdk-pixbuf operations can cause errors in this domain, or in the G_FILE_ERROR domain.

Members

GDK_PIXBUF_ERROR_CORRUPT_IMAGE

An image file was broken somehow.

 

GDK_PIXBUF_ERROR_INSUFFICIENT_MEMORY

Not enough memory.

 

GDK_PIXBUF_ERROR_BAD_OPTION

A bad option was passed to a pixbuf save module.

 

GDK_PIXBUF_ERROR_UNKNOWN_TYPE

Unknown image type.

 

GDK_PIXBUF_ERROR_UNSUPPORTED_OPERATION

Don't know how to perform the given operation on the type of image at hand.

 

GDK_PIXBUF_ERROR_FAILED

Generic failure code, something went wrong.

 

GDK_PIXBUF_ERROR_INCOMPLETE_ANIMATION

Only part of the animation was loaded.

 

GDK_PIXBUF_ERROR

#define GDK_PIXBUF_ERROR gdk_pixbuf_error_quark ()

Error domain used for pixbuf operations. Indicates that the error code will be in the GdkPixbufError enumeration. See GError for information on error domains and error codes.


enum GdkColorspace

This enumeration defines the color spaces that are supported by the gdk-pixbuf library. Currently only RGB is supported.

Members

GDK_COLORSPACE_RGB

Indicates a red/green/blue additive color space.

 

enum GdkPixbufAlphaMode

These values can be passed to gdk_pixbuf_render_to_drawable_alpha() to control how the alpha channel of an image should be handled. This function can create a bilevel clipping mask (black and white) and use it while painting the image. In the future, when the X Window System gets an alpha channel extension, it will be possible to do full alpha compositing onto arbitrary drawables. For now both cases fall back to a bilevel clipping mask.

Members

GDK_PIXBUF_ALPHA_BILEVEL

A bilevel clipping mask (black and white) will be created and used to draw the image. Pixels below 0.5 opacity will be considered fully transparent, and all others will be considered fully opaque.

 

GDK_PIXBUF_ALPHA_FULL

For now falls back to GDK_PIXBUF_ALPHA_BILEVEL. In the future it will do full alpha compositing.

 

GdkPixbuf

typedef struct _GdkPixbuf GdkPixbuf;

This is the main structure in the gdk-pixbuf library. It is used to represent images. It contains information about the image's pixel data, its color space, bits per sample, width and height, and the rowstride (the number of bytes between the start of one row and the start of the next).

Property Details

The “bits-per-sample” property

  “bits-per-sample”          gint

The number of bits per sample. Currently only 8 bit per sample are supported.

Flags: Read / Write / Construct Only

Allowed values: [1,16]

Default value: 8


The “colorspace” property

  “colorspace”               GdkColorspace

The colorspace in which the samples are interpreted.

Flags: Read / Write / Construct Only

Default value: GDK_COLORSPACE_RGB


The “has-alpha” property

  “has-alpha”                gboolean

Whether the pixbuf has an alpha channel.

Flags: Read / Write / Construct Only

Default value: FALSE


The “height” property

  “height”                   gint

The number of rows of the pixbuf.

Flags: Read / Write / Construct Only

Allowed values: >= 1

Default value: 1


The “n-channels” property

  “n-channels”               gint

The number of samples per pixel. Currently, only 3 or 4 samples per pixel are supported.

Flags: Read / Write / Construct Only

Allowed values: >= 0

Default value: 3


The “pixel-bytes” property

  “pixel-bytes”              GBytes *

Readonly pixel data.

Flags: Read / Write / Construct Only


The “pixels” property

  “pixels”                   gpointer

A pointer to the pixel data of the pixbuf.

Flags: Read / Write / Construct Only


The “rowstride” property

  “rowstride”                gint

The number of bytes between the start of a row and the start of the next row. This number must (obviously) be at least as large as the width of the pixbuf.

Flags: Read / Write / Construct Only

Allowed values: >= 1

Default value: 1


The “width” property

  “width”                    gint

The number of columns of the pixbuf.

Flags: Read / Write / Construct Only

Allowed values: >= 1

Default value: 1