get_framegrabber_callback — Query callback function of an image acquisition device.
The operator get_framegrabber_callback queries a callback function for the image acquisition device specified by AcqHandle. If the callback function was registered via set_framegrabber_callback before, CallbackFunction contains a pointer to it, otherwise NULL. Furthermore, UserContext contains a pointer to the user-specific context data that was set via set_framegrabber_callback (or NULL).
With the parameter CallbackType, you can select different callback types. Suggested values are:
The image acquisition has raised an exception.
The exposure of the next image has been finished.
The exposure of the next image has been started.
A new image is ready to be fetched by grab_image_async.
Depending on the functionality of the underlying API, additional values for CallbackType are possible. All actually supported callback types of a specific image acquisition device can be queried by calling get_framegrabber_param with the parameter 'available_callback_types'. For more details see the documentation of the specific image acquisition interface.
Basically an image acquisition handle AcqHandle cannot be used in multiple threads. However, possible exceptions are described in the specific reference documentation of the respective image acquisition interface. Different image acquisition handles can be used safely with different threads for each handle.
For a multithreaded application all image acquisition operators (as listed in open_framegrabber) are an own group in which info_framegrabber, open_framegrabber, close_framegrabber and close_all_framegrabbers are executed exclusively.
get_framegrabber_callback runs in parallel with all non-exclusive operators inside and outside of this group.
Handle of the acquisition device to be used.
Default value: 'transfer_end'
Suggested values: 'exception', 'exposure_end', 'exposure_start', 'transfer_end'
Pointer to the callback function.
Pointer to user-specific context data.
If the image acquisition device is open and the specified callback type is supported, the operator get_framegrabber_callback returns the value 2 (H_MSG_TRUE). Otherwise an exception is raised.
grab_image, grab_data, grab_image_start, grab_image_async, grab_data_async, set_framegrabber_param, close_framegrabber
open_framegrabber, info_framegrabber, set_framegrabber_callback