grab_image_async — Asynchronous grab of an image from the specified image acquisition device.
grab_image_async requests an asynchronously grabbed
image from the image acquisition device specified by
grab_image_async also starts the next asynchronous grab
before the operator returns.
More information about the behavior of a specific image acquisition device
can be found in the corresponding interface documentation in the directory
The desired operational mode of the image acquisition device as well as a
suitable image part and additional interface-specific settings can be
specified using the operators
The grab is finished by calling
grab_data_async. If more than
MaxDelay ms have passed
since the asynchronous grab was started, the asynchronously grabbed image
is considered as too old and a new image is grabbed, if necessary. If a
negative value is assigned to
MaxDelay, this control mechanism is
To abort the grab, the operator
set_framegrabber_param with the
'do_abort_grab' can be used if the specific image
acquisition interface supports it. Note that as an exception from
the description of the concurrent usage in multiple threads (see below)
'do_abort_grab' can also be used from another thread.
Please note that if you call the operators
grab_image_async, the asynchronous grab
grab_image_async is aborted and a new
synchronous grab is started.
For a multithreaded application all image acquisition operators
(as listed in
an own group in which
grab_image_async runs in parallel with all non-exclusive
operators inside and outside of this group.
→object (byte / int2)
Handle of the acquisition device to be used.
Maximum tolerated delay between the start of the asynchronous grab and the delivery of the image [ms].
Default value: -1.0
Suggested values: -1.0, 20.0, 33.3, 40.0, 66.6, 80.0, 99.9
* Select a suitable image acquisition interface named AcqName open_framegrabber('AcqName', 1, 1, 0, 0, 0, 0, 'default' ,-1 , \ 'default' ,-1.0, 'default', 'default', 'default', -1, \ -1, AcqHandle) * Grab image + start next grab grab_image_async(Image1, AcqHandle, -1.0) * Process Image1 ... * Finish asynchronous grab + start next grab grab_image_async(Image2, AcqHandle, -1.0) * Process Image2 ... close_framegrabber(AcqHandle)
If the image acquisition device is open and supports asynchronous grabbing
grab_image_async returns the value 2 (H_MSG_TRUE).
Otherwise an exception is raised.