Incremental image loader. More...
#include <gdkmm/pixbufloader.h>
Static Public Member Functions | |
| static GType | get_type () |
| Get the GType for this class, for use with the underlying GObject type system. | |
| static Glib::RefPtr< PixbufLoader > | create () |
| Creates a new pixbuf loader object. | |
| static Glib::RefPtr< PixbufLoader > | create (const Glib::ustring &image_type, bool mime_type=false) |
| Constructs a pixbuf loader object for a specific image type. | |
Related Symbols | |
(Note that these are not member symbols.) | |
| Glib::RefPtr< Gdk::PixbufLoader > | wrap (GdkPixbufLoader *object, bool take_copy=false) |
| A Glib::wrap() method for this object. | |
Additional Inherited Members | |
 Public Types inherited from Glib::Object | |
| typedef void(*)(gpointer data | DestroyNotify) |
| Public Types inherited from sigc::trackable | |
| typedef internal::func_destroy_notify | func_destroy_notify |
| Public Types inherited from sigc::notifiable | |
| typedef internal::func_destroy_notify | func_destroy_notify |
Detailed Description
Incremental image loader.
Gdk::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::create_from_file() or Gdk::PixbufAnimation::create_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:
- signal_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.
- signal_area_prepared() will be emitted as soon as the pixbuf of the desired size has been allocated. You can obtain the Gdk::Pixbuf instance by calling get_pixbuf(). You can also call get_pixbuf() later to get the same pixbuf.
- signal_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 signal_area_prepared() has been emitted, you can call get_animation() to get the Gdk::PixbufAnimation instance, and then call and Gdk::PixbufAnimation::get_iter() to get a Gdk::PixbufAnimationIter to retrieve the pixbuf for the desired time stamp.
Constructor & Destructor Documentation
◆ PixbufLoader() [1/3]
|
noexcept |
◆ ~PixbufLoader()
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overridenoexcept |
◆ PixbufLoader() [2/3]
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protected |
Constructs a pixbuf loader object.
◆ PixbufLoader() [3/3]
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explicitprotected |
Constructs a pixbuf loader object for a specific image type.
Constructs 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. 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 image_type can be one of the types returned by Gdk::Pixbuf::get_formats(), or a MIME type.
Common MIME Types are listed here http://www.iana.org/assignments/media-types/ and here: http://www.freedesktop.org/Software/shared-mime-info
The list of non-mime-type 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 PixbufFormat::get_name() on each of the PixbufFormats returned by Gdk::Pixbuf::get_formats().
- Parameters
-
image_type Name of the image format to be loaded with the image. mime_type If this is true then the image_type is a MIME type.
- Exceptions
-
Gdk::PixbufError
Member Function Documentation
◆ close()
| void Gdk::PixbufLoader::close | ( | ) |
Informs a pixbuf loader that no further writes with PixbufLoader::write() will occur, so that it can free its internal loading structures.
Also, tries to parse any data that hasn't yet been parsed; if the remaining data is partial or corrupt, an exception will be thrown. If you're just cancelling a load rather than expecting it to be finished, writing an empty catch() block to ignore errors is reasonable.
- Exceptions
-
Gdk::PixbufError Glib::FileError
◆ create() [1/2]
|
static |
Creates a new pixbuf loader object.
- Returns
- A newly-created pixbuf loader.
◆ create() [2/2]
|
static |
Constructs a pixbuf loader object for a specific image type.
Constructs 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. 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 image_type can be one of the types returned by Gdk::Pixbuf::get_formats(), or a MIME type.
Common MIME Types are listed here http://www.iana.org/assignments/media-types/ and here: http://www.freedesktop.org/Software/shared-mime-info
The list of non-mime-type 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 PixbufFormat::get_name() on each of the PixbufFormats returned by Gdk::Pixbuf::get_formats().
- Parameters
-
image_type Name of the image format to be loaded with the image. mime_type If this is true then the image_type is a MIME type.
- Exceptions
-
Gdk::PixbufError
◆ get_animation()
| Glib::RefPtr< Gdk::PixbufAnimation > Gdk::PixbufLoader::get_animation | ( | ) |
Queries the Gdk::PixbufAnimation that a pixbuf loader is currently creating.
In general it only makes sense to call this function after the GdkPixbuf::PixbufLoader::signal_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 nullptr.
- Returns
- The animation that the loader is currently loading.
◆ get_format()
| PixbufFormat Gdk::PixbufLoader::get_format | ( | ) | const |
Obtains the available information about the format of the currently loading image file.
- Returns
- A Gdk::PixbufFormat.
◆ get_pixbuf()
| Glib::RefPtr< Gdk::Pixbuf > Gdk::PixbufLoader::get_pixbuf | ( | ) |
Queries the Gdk::Pixbuf that a pixbuf loader is currently creating.
In general it only makes sense to call this function after the GdkPixbuf::PixbufLoader::signal_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 nullptr.
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 Gdk::PixbufAnimation::get_static_image()).
- Returns
- The pixbuf that the loader is creating.
◆ get_type()
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static |
Get the GType for this class, for use with the underlying GObject type system.
◆ gobj() [1/2]
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inline |
Provides access to the underlying C GObject.
◆ gobj() [2/2]
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inline |
Provides access to the underlying C GObject.
◆ gobj_copy()
| GdkPixbufLoader * Gdk::PixbufLoader::gobj_copy | ( | ) |
Provides access to the underlying C instance. The caller is responsible for unrefing it. Use when directly setting fields in structs.
◆ on_area_prepared()
This is a default handler for the signal signal_area_prepared().
◆ on_area_updated()
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protectedvirtual |
This is a default handler for the signal signal_area_updated().
◆ on_closed()
This is a default handler for the signal signal_closed().
◆ on_size_prepared()
This is a default handler for the signal signal_size_prepared().
◆ operator=()
|
noexcept |
◆ set_size()
| void Gdk::PixbufLoader::set_size | ( | int | width, |
| int | height | ||
| ) |
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 signal_size_prepared() signal.
Attempts to set the desired image size are ignored after the emission of the signal_size_prepared() signal.
- Parameters
-
width The desired width of the image being loaded. height The desired height of the image being loaded.
◆ signal_area_prepared()
| Glib::SignalProxy< void()> Gdk::PixbufLoader::signal_area_prepared | ( | ) |
- Slot Prototype:
void on_my_area_prepared()
Flags: Run Last
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::PixbufLoader::get_pixbuf() to fetch the partially-loaded pixbuf.
◆ signal_area_updated()
| Glib::SignalProxy< void(int, int, int, int)> Gdk::PixbufLoader::signal_area_updated | ( | ) |
- Slot Prototype:
void on_my_area_updated(int x, int y, int width, int height)
Flags: Run Last
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.
◆ signal_closed()
| Glib::SignalProxy< void()> Gdk::PixbufLoader::signal_closed | ( | ) |
- Slot Prototype:
void on_my_closed()
Flags: Run Last
This signal is emitted when Gdk::PixbufLoader::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.
◆ signal_size_prepared()
| Glib::SignalProxy< void(int, int)> Gdk::PixbufLoader::signal_size_prepared | ( | ) |
- Slot Prototype:
void on_my_size_prepared(int width, int height)
Flags: Run Last
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::PixbufLoader::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.
◆ write()
Causes the pixbuf loader to parse the next count bytes of an image.
It will return if the data was loaded successfully, and throw an exception if an error occurred. In the latter case, the loader will be closed, and will not accept further writes.
- Parameters
-
buf Pointer to image data. count Length of the buf buffer in bytes.
- Exceptions
-
Gdk::PixbufError Glib::FileError
Friends And Related Symbol Documentation
◆ wrap()
|
related |
A Glib::wrap() method for this object.
- Parameters
-
object The C instance. take_copy False if the result should take ownership of the C instance. True if it should take a new copy or ref.
- Returns
- A C++ instance that wraps this C instance.
