PixbufLoader

class PixbufLoader(**properties: Any)

Superclasses: Object

Incremental image loader.

GdkPixbufLoader provides a way for applications to drive the process of loading an image, by letting them send the image data directly to the loader instead of having the loader read the data from a file. Applications can use this functionality instead of :func:`~gi.repository.GdkPixbuf.Pixbuf.new_from_file` or :func:`~gi.repository.GdkPixbuf.PixbufAnimation.new_from_file` when they need to parse image data in small chunks. For example, it should be used when reading an image from a (potentially) slow network connection, or when loading an extremely large file.

To use GdkPixbufLoader to load an image, create a new instance, and call write to send the data to it. When done, close should be called to end the stream and finalize everything.

The loader will emit three important signals throughout the process:

  • size_prepared will be emitted as soon as the image has enough information to determine the size of the image to be used. If you want to scale the image while loading it, you can call set_size in response to this signal.

  • area_prepared will be emitted as soon as the pixbuf of the desired has been allocated. You can obtain the GdkPixbuf instance by calling get_pixbuf. If you want to use it, simply acquire a reference to it. You can also call :func:`~gi.repository.GdkPixbuf.PixbufLoader.get_pixbuf` later to get the same pixbuf.

  • area_updated will be emitted every time a region is updated. This way you can update a partially completed image. Note that you do not know anything about the completeness of an image from the updated area. For example, in an interlaced image you will need to make several passes before the image is done loading.

Loading an animation

Loading an animation is almost as easy as loading an image. Once the first area_prepared signal has been emitted, you can call get_animation to get the PixbufAnimation instance, and then call and get_iter to get a PixbufAnimationIter to retrieve the pixbuf for the desired time stamp.

Constructors

class PixbufLoader
classmethod new() → PixbufLoader

Creates a new pixbuf loader object.

classmethod new_with_mime_type(mime_type: str) → PixbufLoader

Creates a new pixbuf loader object that always attempts to parse image data as if it were an image of MIME type mime_type, instead of identifying the type automatically.

This function is useful if you want an error if the image isn’t the expected MIME type; for loading image formats that can’t be reliably identified by looking at the data; or if the user manually forces a specific MIME type.

The list of supported mime types depends on what image loaders are installed, but typically “image/png”, “image/jpeg”, “image/gif”, “image/tiff” and “image/x-xpixmap” are among the supported mime types. To obtain the full list of supported mime types, call get_mime_types() on each of the PixbufFormat structs returned by get_formats().

Added in version 2.4.

Parameters:

mime_type – the mime type to be loaded

classmethod new_with_type(image_type: str) → PixbufLoader

Creates a new pixbuf loader object that always attempts to parse image data as if it were an image of type image_type, instead of identifying the type automatically.

This function is useful if you want an error if the image isn’t the expected type; for loading image formats that can’t be reliably identified by looking at the data; or if the user manually forces a specific type.

The list of supported image formats depends on what image loaders are installed, but typically “png”, “jpeg”, “gif”, “tiff” and “xpm” are among the supported formats. To obtain the full list of supported image formats, call get_name() on each of the PixbufFormat structs returned by get_formats().

Parameters:

image_type – name of the image format to be loaded with the image

Methods

class PixbufLoader
close() → bool

Informs a pixbuf loader that no further writes with write() will occur, so that it can free its internal loading structures.

This function also tries to parse any data that hasn’t yet been parsed; if the remaining data is partial or corrupt, an error will be returned.

If FALSE is returned, error will be set to an error from the GDK_PIXBUF_ERROR or G_FILE_ERROR domains.

If you’re just cancelling a load rather than expecting it to be finished, passing NULL for error to ignore it is reasonable.

Remember that this function does not release a reference on the loader, so you will need to explicitly release any reference you hold.

get_animation() → PixbufAnimation | None

Queries the PixbufAnimation that a pixbuf loader is currently creating.

In general it only makes sense to call this function after the area_prepared signal has been emitted by the loader.

If the loader doesn’t have enough bytes yet, and hasn’t emitted the area-prepared signal, this function will return NULL.

get_format() → PixbufFormat | None

Obtains the available information about the format of the currently loading image file.

Added in version 2.2.

get_pixbuf() → Pixbuf | None

Queries the Pixbuf that a pixbuf loader is currently creating.

In general it only makes sense to call this function after the area_prepared signal has been emitted by the loader; this means that enough data has been read to know the size of the image that will be allocated.

If the loader has not received enough data via write(), then this function returns NULL.

The returned pixbuf will be the same in all future calls to the loader, so if you want to keep using it, you should acquire a reference to it.

Additionally, if the loader is an animation, it will return the “static image” of the animation (see get_static_image()).

set_size(width: int, height: int) → None

Causes the image to be scaled while it is loaded.

The desired image size can be determined relative to the original size of the image by calling set_size() from a signal handler for the ::size-prepared signal.

Attempts to set the desired image size are ignored after the emission of the ::size-prepared signal.

Added in version 2.2.

Parameters:

  • width – The desired width of the image being loaded.

  • height – The desired height of the image being loaded.

write(buf: Sequence[int]) → bool

Parses the next count bytes in the given image buffer.

Parameters:

buf – Pointer to image data.

write_bytes(buffer: Bytes) → bool

Parses the next contents of the given image buffer.

Added in version 2.30.

Parameters:

buffer – The image data as a GBytes buffer.

Signals

class PixbufLoader.signals
area_prepared() → None

This signal is emitted when the pixbuf loader has allocated the pixbuf in the desired size.

After this signal is emitted, applications can call get_pixbuf() to fetch the partially-loaded pixbuf.

area_updated(x: int, y: int, width: int, height: int) → None

This signal is emitted when a significant area of the image being loaded has been updated.

Normally it means that a complete scanline has been read in, but it could be a different area as well.

Applications can use this signal to know when to repaint areas of an image that is being loaded.

Parameters:

  • x – X offset of upper-left corner of the updated area.

  • y – Y offset of upper-left corner of the updated area.

  • width – Width of updated area.

  • height – Height of updated area.

closed() → None

This signal is emitted when close() is called.

It can be used by different parts of an application to receive notification when an image loader is closed by the code that drives it.

size_prepared(width: int, height: int) → None

This signal is emitted when the pixbuf loader has been fed the initial amount of data that is required to figure out the size of the image that it will create.

Applications can call set_size() in response to this signal to set the desired size to which the image should be scaled.

Parameters:

  • width – the original width of the image

  • height – the original height of the image

Virtual Methods

class PixbufLoader
do_area_prepared() → None
do_area_updated(x: int, y: int, width: int, height: int) → None
Parameters:

  • x

  • y

  • width

  • height

do_closed() → None
do_size_prepared(width: int, height: int) → None
Parameters:

  • width

  • height

Fields

class PixbufLoader
parent_instance
priv