grab_data_asyncT_grab_data_asyncGrabDataAsyncGrabDataAsyncgrab_data_async (Operator)

Name

grab_data_asyncT_grab_data_asyncGrabDataAsyncGrabDataAsyncgrab_data_async — Asynchronous grab of images and preprocessed image data from the specified image acquisition device.

Signature

Description

The operator grab_data_asyncgrab_data_asyncGrabDataAsyncGrabDataAsyncGrabDataAsyncgrab_data_async requests asynchronously grabbed images and preprocessed image data from the image acquisition device specified by AcqHandleAcqHandleAcqHandleAcqHandleacqHandleacq_handle. By default, grab_data_asyncgrab_data_asyncGrabDataAsyncGrabDataAsyncGrabDataAsyncgrab_data_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. 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. Depending on the current configuration of the image acquisition device, the preprocessed image data can be returned in terms of images (ImageImageImageImageimageimage), regions (RegionRegionRegionRegionregionregion), XLD contours (ContoursContoursContoursContourscontourscontours), and control data (DataDataDataDatadatadata).

The grab of the next image is finished by calling grab_data_asyncgrab_data_asyncGrabDataAsyncGrabDataAsyncGrabDataAsyncgrab_data_async or grab_image_asyncgrab_image_asyncGrabImageAsyncGrabImageAsyncGrabImageAsyncgrab_image_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_data_asyncgrab_data_asyncGrabDataAsyncGrabDataAsyncGrabDataAsyncgrab_data_async, the asynchronous grab started by grab_data_asyncgrab_data_asyncGrabDataAsyncGrabDataAsyncGrabDataAsyncgrab_data_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_data_asyncgrab_data_asyncGrabDataAsyncGrabDataAsyncGrabDataAsyncgrab_data_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

Example (HDevelop)

* Select a suitable image acquisition interface name AcqName
open_framegrabber(AcqName,1,1,0,0,0,0,'default',-1,'default',-1.0, \
                  'default','default','default',-1,-1,AcqHandle)
* Grab image, segment it, and start next grab
grab_data_async (Image1, Region1, Contours1, AcqHandle, -1.0, Data1)
* Process data 1...
* Finish asynchronous grab, segment this image, and start next grab
grab_data_async (Image2, Region2, Contours2, AcqHandle, -1.0, Data2)
* Process data 2...
close_framegrabber(AcqHandle)

Result

If the image acquisition device is open and supports the image acquisition via grab_data_asyncgrab_data_asyncGrabDataAsyncGrabDataAsyncGrabDataAsyncgrab_data_async, the operator grab_data_asyncgrab_data_asyncGrabDataAsyncGrabDataAsyncGrabDataAsyncgrab_data_async returns the value TRUE. Otherwise an exception is raised.

Possible Predecessors

open_framegrabberopen_framegrabberOpenFramegrabberOpenFramegrabberOpenFramegrabberopen_framegrabber, grab_image_startgrab_image_startGrabImageStartGrabImageStartGrabImageStartgrab_image_start, set_framegrabber_paramset_framegrabber_paramSetFramegrabberParamSetFramegrabberParamSetFramegrabberParamset_framegrabber_param

Possible Successors

grab_image_asyncgrab_image_asyncGrabImageAsyncGrabImageAsyncGrabImageAsyncgrab_image_async, set_framegrabber_paramset_framegrabber_paramSetFramegrabberParamSetFramegrabberParamSetFramegrabberParamset_framegrabber_param, close_framegrabberclose_framegrabberCloseFramegrabberCloseFramegrabberCloseFramegrabberclose_framegrabber

See also

open_framegrabberopen_framegrabberOpenFramegrabberOpenFramegrabberOpenFramegrabberopen_framegrabber, info_framegrabberinfo_framegrabberInfoFramegrabberInfoFramegrabberInfoFramegrabberinfo_framegrabber, set_framegrabber_paramset_framegrabber_paramSetFramegrabberParamSetFramegrabberParamSetFramegrabberParamset_framegrabber_param

Module

Foundation