Class

GdkPixbufPixbuf

Description [src]

final class GdkPixbuf.Pixbuf : GObject.Object {
  /* No available fields */
}

A pixel buffer.

GdkPixbuf contains information about an 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).

Creating new GdkPixbuf

The most basic way to create a pixbuf is to wrap an existing pixel buffer with a GdkPixbuf instance. You can use the gdk_pixbuf_new_from_data() function to do this.

Every time you create a new GdkPixbuf instance for some data, you will need to specify the destroy notification function that will be called when the data buffer needs to be freed; this will happen when a GdkPixbuf is finalized by the reference counting functions. If you have a chunk of static data compiled into your application, you can pass in NULL as the destroy notification function so that the data will not be freed.

The gdk_pixbuf_new() constructor function can be used as a convenience to create a pixbuf with an empty buffer; this is equivalent to allocating a data buffer using malloc() and then wrapping it with gdk_pixbuf_new_from_data(). The gdk_pixbuf_new() function will compute an optimal rowstride so that rendering can be performed with an efficient algorithm.

As a special case, you can use the gdk_pixbuf_new_from_xpm_data() function to create a pixbuf from inline XPM image data.

You can also copy an existing pixbuf with the gdk_pixbuf_copy() function. This is not the same as just acquiring a reference to the old pixbuf instance: the copy function will actually duplicate the pixel data in memory and create a new GdkPixbuf instance for it.

Reference counting

GdkPixbuf structures are reference counted. This means that an application can share a single pixbuf among many parts of the code. When a piece of the program needs to use a pixbuf, it should acquire a reference to it by calling g_object_ref(); when it no longer needs the pixbuf, it should release the reference it acquired by calling g_object_unref(). The resources associated with a GdkPixbuf will be freed when its reference count drops to zero. Newly-created GdkPixbuf instances start with a reference count of one.

Image Data

Image data in a pixbuf is stored in memory in an 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.

NOTE: If you are copying raw pixbuf data with memcpy() 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:

last_row = width * ((n_channels * bits_per_sample + 7) / 8);

The same rule applies when iterating over each row of a GdkPixbuf pixels array.

The following code illustrates a simple put_pixel() function for RGB pixbufs with 8 bits per channel with an alpha channel.

static void
put_pixel (GdkPixbuf *pixbuf,
           int x,
       int y,
       guchar red,
       guchar green,
       guchar blue,
       guchar alpha)
{
  int n_channels = gdk_pixbuf_get_n_channels (pixbuf);

  // Ensure that the pixbuf is valid
  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);

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

  // Ensure that the coordinates are in a valid range
  g_assert (x >= 0 && x < width);
  g_assert (y >= 0 && y < height);

  int rowstride = gdk_pixbuf_get_rowstride (pixbuf);

  // The pixel buffer in the GdkPixbuf instance
  guchar *pixels = gdk_pixbuf_get_pixels (pixbuf);

  // The pixel we wish to modify
  guchar *p = pixels + y * rowstride + x * n_channels;
  p[0] = red;
  p[1] = green;
  p[2] = blue;
  p[3] = alpha;
}

Loading images

The GdkPixBuf class provides a simple mechanism for loading an image from a file in synchronous and asynchronous fashion.

For GUI applications, it is recommended to use the asynchronous stream API to avoid blocking the control flow of the application.

Additionally, GdkPixbuf provides the GdkPixbufLoader API for progressive image loading.

Saving images

The GdkPixbuf class provides methods for saving image data in a number of file formats. The formatted data can be written to a file or to a memory buffer. GdkPixbuf can also call a user-defined callback on the data, which allows to e.g. write the image to a socket or store it in a database.

Ancestors

Implements

Constructors

gdk_pixbuf_new

Creates a new GdkPixbuf structure and allocates a buffer for it.

gdk_pixbuf_new_from_bytes

Creates a new GdkPixbuf out of in-memory readonly image data.

Available since: 2.32

gdk_pixbuf_new_from_data

Creates a new GdkPixbuf out of in-memory image data.

gdk_pixbuf_new_from_file

Creates a new pixbuf by loading an image from a file.

gdk_pixbuf_new_from_file_at_scale

Creates a new pixbuf by loading an image from a file.

Available since: 2.6

gdk_pixbuf_new_from_file_at_size

Creates a new pixbuf by loading an image from a file.

Available since: 2.4

gdk_pixbuf_new_from_inline

Creates a GdkPixbuf from a flat representation that is suitable for storing as inline data in a program.

Deprecated since: 2.32

gdk_pixbuf_new_from_resource

Creates a new pixbuf by loading an image from an resource.

Available since: 2.26

gdk_pixbuf_new_from_resource_at_scale

Creates a new pixbuf by loading an image from an resource.

Available since: 2.26

gdk_pixbuf_new_from_stream

Creates a new pixbuf by loading an image from an input stream.

Available since: 2.14

gdk_pixbuf_new_from_stream_at_scale

Creates a new pixbuf by loading an image from an input stream.

Available since: 2.14

gdk_pixbuf_new_from_stream_finish

Finishes an asynchronous pixbuf creation operation started with gdk_pixbuf_new_from_stream_async().

Available since: 2.24

gdk_pixbuf_new_from_xpm_data

Creates a new pixbuf by parsing XPM data in memory.

Functions

gdk_pixbuf_calculate_rowstride

Calculates the rowstride that an image created with those values would have.

Available since: 2.36.8

gdk_pixbuf_get_file_info

Parses an image file far enough to determine its format and size.

Available since: 2.4

gdk_pixbuf_get_file_info_async

Asynchronously parses an image file far enough to determine its format and size.

Available since: 2.32

gdk_pixbuf_get_file_info_finish

Finishes an asynchronous pixbuf parsing operation started with gdk_pixbuf_get_file_info_async().

Available since: 2.32

gdk_pixbuf_get_formats

Obtains the available information about the image formats supported by GdkPixbuf.

Available since: 2.2

gdk_pixbuf_init_modules

Initalizes the gdk-pixbuf loader modules referenced by the loaders.cache file present inside that directory.

Available since: 2.40

gdk_pixbuf_new_from_stream_async

Creates a new pixbuf by asynchronously loading an image from an input stream.

Available since: 2.24

gdk_pixbuf_new_from_stream_at_scale_async

Creates a new pixbuf by asynchronously loading an image from an input stream.

Available since: 2.24

gdk_pixbuf_save_to_stream_finish

Finishes an asynchronous pixbuf save operation started with gdk_pixbuf_save_to_stream_async().

Available since: 2.24

Instance methods

gdk_pixbuf_add_alpha

Takes an existing pixbuf and adds an alpha channel to it.

gdk_pixbuf_apply_embedded_orientation

Takes an existing pixbuf and checks for the presence of an associated “orientation” option.

Available since: 2.12

gdk_pixbuf_composite

Creates a transformation of the source image src by scaling by scale_x and scale_y then translating by offset_x and offset_y.

gdk_pixbuf_composite_color

Creates a transformation of the source image src by scaling by scale_x and scale_y then translating by offset_x and offset_y, then alpha blends the rectangle (dest_x ,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 image.

gdk_pixbuf_composite_color_simple

Creates a new pixbuf by scaling src to dest_width x dest_height and alpha blending the result with a checkboard of colors color1 and color2.

gdk_pixbuf_copy

Creates a new GdkPixbuf with a copy of the information in the specified pixbuf.

gdk_pixbuf_copy_area

Copies a rectangular area from src_pixbuf to dest_pixbuf.

gdk_pixbuf_copy_options

Copies the key/value pair options attached to a GdkPixbuf to another GdkPixbuf.

Available since: 2.36

gdk_pixbuf_fill

Clears a pixbuf to the given RGBA value, converting the RGBA value into the pixbuf’s pixel format.

gdk_pixbuf_flip

Flips a pixbuf horizontally or vertically and returns the result in a new pixbuf.

Available since: 2.6

gdk_pixbuf_get_bits_per_sample

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

gdk_pixbuf_get_byte_length

Returns the length of the pixel data, in bytes.

Available since: 2.26

gdk_pixbuf_get_colorspace

Queries the color space of a pixbuf.

gdk_pixbuf_get_has_alpha

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

gdk_pixbuf_get_height

Queries the height of a pixbuf.

gdk_pixbuf_get_n_channels

Queries the number of channels of a pixbuf.

gdk_pixbuf_get_option

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().

gdk_pixbuf_get_options

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().

Available since: 2.32

gdk_pixbuf_get_pixels

Queries a pointer to the pixel data of a pixbuf.

gdk_pixbuf_get_pixels_with_length

Queries a pointer to the pixel data of a pixbuf.

Available since: 2.26

gdk_pixbuf_get_rowstride

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.

gdk_pixbuf_get_width

Queries the width of a pixbuf.

gdk_pixbuf_new_subpixbuf

Creates a new pixbuf which represents a sub-region of src_pixbuf.

gdk_pixbuf_read_pixel_bytes

Provides a GBytes buffer containing the raw pixel data; the data must not be modified.

Available since: 2.32

gdk_pixbuf_read_pixels

Provides a read-only pointer to the raw pixel data.

Available since: 2.32

gdk_pixbuf_ref

Adds a reference to a pixbuf.

Deprecated since: 2.0

gdk_pixbuf_remove_option

Removes the key/value pair option attached to a GdkPixbuf.

Available since: 2.36

gdk_pixbuf_rotate_simple

Rotates a pixbuf by a multiple of 90 degrees, and returns the result in a new pixbuf.

Available since: 2.6

gdk_pixbuf_saturate_and_pixelate

Modifies saturation and optionally pixelates src, placing the result in dest.

gdk_pixbuf_save

Saves pixbuf to a file in format type. By default, “jpeg”, “png”, “ico” and “bmp” are possible file formats to save in, but more formats may be installed. The list of all writable formats can be determined in the following way:

gdk_pixbuf_save_to_buffer

Saves pixbuf to a new buffer in format type, which is currently “jpeg”, “png”, “tiff”, “ico” or “bmp”.

Available since: 2.4

gdk_pixbuf_save_to_bufferv

Vector version of gdk_pixbuf_save_to_buffer().

Available since: 2.4

gdk_pixbuf_save_to_callback

Saves pixbuf in format type by feeding the produced data to a callback.

Available since: 2.4

gdk_pixbuf_save_to_callbackv

Vector version of gdk_pixbuf_save_to_callback().

Available since: 2.4

gdk_pixbuf_save_to_stream

Saves pixbuf to an output stream.

Available since: 2.14

gdk_pixbuf_save_to_stream_async

Saves pixbuf to an output stream asynchronously.

Available since: 2.24

gdk_pixbuf_save_to_streamv

Saves pixbuf to an output stream.

Available since: 2.36

gdk_pixbuf_save_to_streamv_async

Saves pixbuf to an output stream asynchronously.

Available since: 2.36

gdk_pixbuf_savev

Vector version of gdk_pixbuf_save().

gdk_pixbuf_scale

Creates a transformation of the source image src by scaling by scale_x and scale_y then translating by offset_x and offset_y, then renders the rectangle (dest_x, dest_y, dest_width, dest_height) of the resulting image onto the destination image replacing the previous contents.

gdk_pixbuf_scale_simple

Create a new pixbuf containing a copy of src scaled to dest_width x dest_height.

gdk_pixbuf_set_option

Attaches a key/value pair as an option to a GdkPixbuf.

Available since: 2.2

gdk_pixbuf_unref

Removes a reference from a pixbuf.

Deprecated since: 2.0

Methods inherited from GObject (42)

Properties

GdkPixbuf.Pixbuf:bits-per-sample

The number of bits per sample.

GdkPixbuf.Pixbuf:colorspace

The color space of the pixbuf.

GdkPixbuf.Pixbuf:has-alpha

Whether the pixbuf has an alpha channel.

GdkPixbuf.Pixbuf:height

The number of rows of the pixbuf.

GdkPixbuf.Pixbuf:n-channels

The number of samples per pixel.

GdkPixbuf.Pixbuf:pixel-bytes
No description available.
GdkPixbuf.Pixbuf:pixels

A pointer to the pixel data of the pixbuf.

GdkPixbuf.Pixbuf:rowstride

The number of bytes between the start of a row and the start of the next row.

GdkPixbuf.Pixbuf:width

The number of columns of the pixbuf.

Signals

Signals inherited from GObject (1)