grab_image_asyncT_grab_image_asyncGrabImageAsyncGrabImageAsyncgrab_image_async (Operator)
Name
grab_image_asyncT_grab_image_asyncGrabImageAsyncGrabImageAsyncgrab_image_async
— Asynchronous grab of an image from the specified image acquisition device.
Signature
Description
The operator grab_image_asyncgrab_image_asyncGrabImageAsyncGrabImageAsyncGrabImageAsyncgrab_image_async
requests an asynchronously grabbed
image from the image acquisition device specified by AcqHandleAcqHandleAcqHandleAcqHandleacqHandleacq_handle
.
By default, grab_image_asyncgrab_image_asyncGrabImageAsyncGrabImageAsyncGrabImageAsyncgrab_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
'doc/html/reference/acquisition'"doc/html/reference/acquisition""doc/html/reference/acquisition""doc/html/reference/acquisition""doc/html/reference/acquisition""doc/html/reference/acquisition".
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 open_framegrabberopen_framegrabberOpenFramegrabberOpenFramegrabberOpenFramegrabberopen_framegrabber
and
set_framegrabber_paramset_framegrabber_paramSetFramegrabberParamSetFramegrabberParamSetFramegrabberParamset_framegrabber_param
.
The grab is finished by calling grab_image_asyncgrab_image_asyncGrabImageAsyncGrabImageAsyncGrabImageAsyncgrab_image_async
or
grab_data_asyncgrab_data_asyncGrabDataAsyncGrabDataAsyncGrabDataAsyncgrab_data_async
. If more than MaxDelayMaxDelayMaxDelayMaxDelaymaxDelaymax_delay
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 MaxDelayMaxDelayMaxDelayMaxDelaymaxDelaymax_delay
, this control mechanism is
deactivated.
To abort the grab, the operator set_framegrabber_paramset_framegrabber_paramSetFramegrabberParamSetFramegrabberParamSetFramegrabberParamset_framegrabber_param
with the
parameter '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_imagegrab_imageGrabImageGrabImageGrabImagegrab_image
or
grab_datagrab_dataGrabDataGrabDataGrabDatagrab_data
after grab_image_asyncgrab_image_asyncGrabImageAsyncGrabImageAsyncGrabImageAsyncgrab_image_async
, the asynchronous grab
started by grab_image_asyncgrab_image_asyncGrabImageAsyncGrabImageAsyncGrabImageAsyncgrab_image_async
is aborted and a new
synchronous grab is started.
Attention
For a multithreaded application all image acquisition operators
(as listed in open_framegrabberopen_framegrabberOpenFramegrabberOpenFramegrabberOpenFramegrabberopen_framegrabber
) are
an own group in which info_framegrabberinfo_framegrabberInfoFramegrabberInfoFramegrabberInfoFramegrabberinfo_framegrabber
, open_framegrabberopen_framegrabberOpenFramegrabberOpenFramegrabberOpenFramegrabberopen_framegrabber
,
close_framegrabberclose_framegrabberCloseFramegrabberCloseFramegrabberCloseFramegrabberclose_framegrabber
and close_all_framegrabbersclose_all_framegrabbersCloseAllFramegrabbersCloseAllFramegrabbersCloseAllFramegrabbersclose_all_framegrabbers
are
executed exclusively.
grab_image_asyncgrab_image_asyncGrabImageAsyncGrabImageAsyncGrabImageAsyncgrab_image_async
runs in parallel with all non-exclusive
operators inside and outside of this group.
Execution Information
- Multithreading type: reentrant (runs in parallel with non-exclusive operators).
- Multithreading scope: global (may be called from any thread).
- Processed without parallelization.
Parameters
ImageImageImageImageimageimage
(output_object) image →
objectHImageHObjectHImageHobject * (byte / int2)
Grabbed image.
AcqHandleAcqHandleAcqHandleAcqHandleacqHandleacq_handle
(input_control) framegrabber →
HFramegrabber, HTupleHHandleHTupleHtuple (handle) (IntPtr) (HHandle) (handle)
Handle of the acquisition device to be used.
MaxDelayMaxDelayMaxDelayMaxDelaymaxDelaymax_delay
(input_control) number →
HTuplefloatHTupleHtuple (real) (double) (double) (double)
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
Example (HDevelop)
* 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)
Result
If the image acquisition device is open and supports asynchronous grabbing
the operator grab_image_asyncgrab_image_asyncGrabImageAsyncGrabImageAsyncGrabImageAsyncgrab_image_async
returns the value TRUE.
Otherwise an exception is raised.
Possible Predecessors
grab_image_startgrab_image_startGrabImageStartGrabImageStartGrabImageStartgrab_image_start
,
open_framegrabberopen_framegrabberOpenFramegrabberOpenFramegrabberOpenFramegrabberopen_framegrabber
,
set_framegrabber_paramset_framegrabber_paramSetFramegrabberParamSetFramegrabberParamSetFramegrabberParamset_framegrabber_param
Possible Successors
grab_data_asyncgrab_data_asyncGrabDataAsyncGrabDataAsyncGrabDataAsyncgrab_data_async
,
set_framegrabber_paramset_framegrabber_paramSetFramegrabberParamSetFramegrabberParamSetFramegrabberParamset_framegrabber_param
,
close_framegrabberclose_framegrabberCloseFramegrabberCloseFramegrabberCloseFramegrabberclose_framegrabber
See also
grab_image_startgrab_image_startGrabImageStartGrabImageStartGrabImageStartgrab_image_start
,
open_framegrabberopen_framegrabberOpenFramegrabberOpenFramegrabberOpenFramegrabberopen_framegrabber
,
info_framegrabberinfo_framegrabberInfoFramegrabberInfoFramegrabberInfoFramegrabberinfo_framegrabber
,
set_framegrabber_paramset_framegrabber_paramSetFramegrabberParamSetFramegrabberParamSetFramegrabberParamset_framegrabber_param
Module
Foundation