Struct gdk_pixbuf::PixbufLoader

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pub struct PixbufLoader { /* private fields */ }
Expand description

Incremental image loader.

PixbufLoader 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 gdk_pixbuf_new_from_file() or gdk_pixbuf_animation_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 PixbufLoader to load an image, create a new instance, and call PixbufLoaderExt::write() to send the data to it. When done, PixbufLoaderExt::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 PixbufLoaderExt::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 Pixbuf instance by calling PixbufLoaderExt::pixbuf(). If you want to use it, simply acquire a reference to it. You can also call gdk_pixbuf_loader_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 PixbufLoaderExt::animation() to get the PixbufAnimation instance, and then call and PixbufAnimationExtManual::iter() to get a PixbufAnimationIter to retrieve the pixbuf for the desired time stamp.

§Signals

§area-prepared

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

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

§area-updated

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.

§closed

This signal is emitted when gdk_pixbuf_loader_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

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 gdk_pixbuf_loader_set_size() in response to this signal to set the desired size to which the image should be scaled.

§Implements

PixbufLoaderExt

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impl PixbufLoader

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pub const NONE: Option<&'static PixbufLoader> = None

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pub fn new() -> PixbufLoader

Creates a new pixbuf loader object.

§Returns

A newly-created pixbuf loader.

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pub fn with_mime_type(mime_type: &str) -> Result<PixbufLoader, Error>

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 gdk_pixbuf_format_get_mime_types() on each of the #GdkPixbufFormat structs returned by gdk_pixbuf_get_formats().

§mime_type

the mime type to be loaded

§Returns

A newly-created pixbuf loader.

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pub fn with_type(image_type: &str) -> Result<PixbufLoader, Error>

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 gdk_pixbuf_format_get_name() on each of the #GdkPixbufFormat structs returned by gdk_pixbuf_get_formats().

§image_type

name of the image format to be loaded with the image

§Returns

A newly-created pixbuf loader.

Trait Implementations§

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impl Clone for PixbufLoader

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fn clone(&self) -> Self

Returns a copy of the value. Read more
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fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more
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impl Debug for PixbufLoader

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fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more
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impl Default for PixbufLoader

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fn default() -> Self

Returns the “default value” for a type. Read more
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impl HasParamSpec for PixbufLoader

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type ParamSpec = ParamSpecObject

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type SetValue = PixbufLoader

Preferred value to be used as setter for the associated ParamSpec.
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type BuilderFn = fn(_: &str) -> ParamSpecObjectBuilder<'_, PixbufLoader>

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fn param_spec_builder() -> Self::BuilderFn

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impl Hash for PixbufLoader

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fn hash<H>(&self, state: &mut H)
where H: Hasher,

Feeds this value into the given Hasher. Read more
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fn hash_slice<H>(data: &[Self], state: &mut H)
where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher. Read more
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impl<T: PixbufLoaderImpl> IsSubclassable<T> for PixbufLoader

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fn class_init(class: &mut Class<Self>)

Override the virtual methods of this class for the given subclass and do other class initialization. Read more
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fn instance_init(instance: &mut InitializingObject<T>)

Instance specific initialization. Read more
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impl Ord for PixbufLoader

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fn cmp(&self, other: &Self) -> Ordering

This method returns an Ordering between self and other. Read more
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fn max(self, other: Self) -> Self
where Self: Sized,

Compares and returns the maximum of two values. Read more
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fn min(self, other: Self) -> Self
where Self: Sized,

Compares and returns the minimum of two values. Read more
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fn clamp(self, min: Self, max: Self) -> Self
where Self: Sized + PartialOrd,

Restrict a value to a certain interval. Read more
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impl ParentClassIs for PixbufLoader

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impl<OT: ObjectType> PartialEq<OT> for PixbufLoader

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fn eq(&self, other: &OT) -> bool

This method tests for self and other values to be equal, and is used by ==.
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fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
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impl<OT: ObjectType> PartialOrd<OT> for PixbufLoader

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fn partial_cmp(&self, other: &OT) -> Option<Ordering>

This method returns an ordering between self and other values if one exists. Read more
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fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator. Read more
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fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator. Read more
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fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator. Read more
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fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator. Read more
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impl StaticType for PixbufLoader

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fn static_type() -> Type

Returns the type identifier of Self.
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impl Eq for PixbufLoader

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fn disconnect(&self, handler_id: SignalHandlerId)

Disconnect a previously connected signal handler.
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fn notify(&self, property_name: &str)

Notify that the given property has changed its value. Read more
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Downgrade this object to a weak reference.
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fn ref_count(&self) -> u32

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Runs the dispose mechanism of the object. Read more
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impl<O> PixbufLoaderExt for O
where O: IsA<PixbufLoader>,

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fn close(&self) -> Result<(), Error>

Informs a pixbuf loader that no further writes with gdk_pixbuf_loader_write() will occur, so that it can free its internal loading structures. Read more
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fn animation(&self) -> Option<PixbufAnimation>

Queries the #GdkPixbufAnimation that a pixbuf loader is currently creating. Read more
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fn format(&self) -> Option<PixbufFormat>

Obtains the available information about the format of the currently loading image file. Read more
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fn pixbuf(&self) -> Option<Pixbuf>

Queries the #GdkPixbuf that a pixbuf loader is currently creating. Read more
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fn set_size(&self, width: i32, height: i32)

Causes the image to be scaled while it is loaded. Read more
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fn write(&self, buf: &[u8]) -> Result<(), Error>

Parses the next count bytes in the given image buffer. Read more
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fn write_bytes(&self, buffer: &Bytes) -> Result<(), Error>

Parses the next contents of the given image buffer. Read more
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fn connect_area_prepared<F: Fn(&Self) + 'static>(&self, f: F) -> SignalHandlerId

This signal is emitted when the pixbuf loader has allocated the pixbuf in the desired size. Read more
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fn connect_area_updated<F: Fn(&Self, i32, i32, i32, i32) + 'static>( &self, f: F ) -> SignalHandlerId

This signal is emitted when a significant area of the image being loaded has been updated. Read more
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fn connect_closed<F: Fn(&Self) + 'static>(&self, f: F) -> SignalHandlerId

This signal is emitted when gdk_pixbuf_loader_close() is called. Read more
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fn connect_size_prepared<F: Fn(&Self, i32, i32) + 'static>( &self, f: F ) -> SignalHandlerId

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. Read more
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impl<T> Property for T
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type Value = T

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type Value = T

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