| The gdk-pixbuf Library | |||
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#include <gdk-pixbuf/gdk-pixbuf.h> GdkPixbufLoader* gdk_pixbuf_loader_new (void); GdkPixbufLoader* gdk_pixbuf_loader_new_with_type (const char *image_type, GError **error); gboolean gdk_pixbuf_loader_write (GdkPixbufLoader *loader, const guchar *buf, gsize count, GError **error); GdkPixbuf* gdk_pixbuf_loader_get_pixbuf (GdkPixbufLoader *loader); GdkPixbufAnimation* gdk_pixbuf_loader_get_animation (GdkPixbufLoader *loader); gboolean gdk_pixbuf_loader_close (GdkPixbufLoader *loader, GError **error); |
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 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 GdkPixbufLoader to load an image, just create a new one, and call gdk_pixbuf_loader_write() to send the data to it. When done, gdk_pixbuf_loader_close() should be called to end the stream and finalize everything. The loader will emit two important signals throughout the process. The first, "area_prepared", will be called as soon as the image has enough information to determine the size of the image to be used. It will pass a GdkPixbuf in. If you want to use it, you can simply ref it. In addition, no actual information will be passed in yet, so the pixbuf can be safely filled with any temporary graphics (or an initial color) as needed. You can also call the gdk_pixbuf_loader_get_pixbuf() once this signal has been emitted and get the same pixbuf.
The other signal, "area_updated" gets called 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 area updated. For example, in an interlaced image, you need to make several passes before the image is done loading.
Loading an animation is almost as easy as loading an image. Once the first "area_prepared" signal has been emitted, you can call gdk_pixbuf_loader_get_animation() to get the GdkPixbufAnimation struct and gdk_pixbuf_animation_get_iter() to get an GdkPixbufAnimationIter for displaying it.
GdkPixbufLoader* gdk_pixbuf_loader_new (void); |
Creates a new pixbuf loader object.
GdkPixbufLoader* gdk_pixbuf_loader_new_with_type (const char *image_type, GError **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. 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.
| image_type : | name of the image format to be loaded with the image |
| error : | return location for an allocated GError, or NULL to ignore errors |
| Returns : | A newly-created pixbuf loader. |
gboolean gdk_pixbuf_loader_write (GdkPixbufLoader *loader, const guchar *buf, gsize count, GError **error); |
This will cause a pixbuf loader to parse the next count bytes of an image. It will return TRUE if the data was loaded successfully, and FALSE if an error occurred. In the latter case, the loader will be closed, and will not accept further writes. If FALSE is returned, error will be set to an error from the GDK_PIXBUF_ERROR or G_FILE_ERROR domains.
GdkPixbuf* gdk_pixbuf_loader_get_pixbuf (GdkPixbufLoader *loader); |
Queries the GdkPixbuf 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 gdk_pixbuf_loader_write(), then this function returns NULL. The returned pixbuf will be the same in all future calls to the loader, so simply calling g_object_ref() should be sufficient to continue using it. Additionally, if the loader is an animation, it will return the "static image" of the animation (see gdk_pixbuf_animation_get_static_image()).
| loader : | A pixbuf loader. |
| Returns : | The GdkPixbuf that the loader is creating, or NULL if not enough data has been read to determine how to create the image buffer. |
GdkPixbufAnimation* gdk_pixbuf_loader_get_animation (GdkPixbufLoader *loader); |
Queries the GdkPixbufAnimation 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 (hasn't emitted the "area_prepared" signal) this function will return NULL.
| loader : | A pixbuf loader |
| Returns : | The GdkPixbufAnimation that the loader is loading, or NULL if not enough data has been read to determine the information. |
gboolean gdk_pixbuf_loader_close (GdkPixbufLoader *loader, GError **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. 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.
| loader : | A pixbuf loader. |
| error : | return location for a GError, or NULL to ignore errors |
| Returns : | TRUE if all image data written so far was successfully passed out via the update_area signal |