grab_data_asyncT_grab_data_asyncGrabDataAsyncGrabDataAsync (Operator)

Name

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

Signature

grab_data_async( : Image, Region, Contours : AcqHandle, MaxDelay : Data)

The operator grab_data_asyncgrab_data_asyncGrabDataAsyncGrabDataAsyncGrabDataAsync requests asynchronously grabbed images and preprocessed image data from the image acquisition device specified by AcqHandleAcqHandleAcqHandleAcqHandleacqHandle. By default, grab_data_asyncgrab_data_asyncGrabDataAsyncGrabDataAsyncGrabDataAsync also starts the next asynchronous grab before the operator returns. More information about the behavior of a specific image acquistion 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". 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_framegrabberOpenFramegrabberOpenFramegrabberOpenFramegrabber and set_framegrabber_paramset_framegrabber_paramSetFramegrabberParamSetFramegrabberParamSetFramegrabberParam. Depending on the current configuration of the image acquisition device, the preprocessed image data can be returned in terms of images (ImageImageImageImageimage), regions (RegionRegionRegionRegionregion), XLD contours (ContoursContoursContoursContourscontours), and control data (DataDataDataDatadata).

The grab of the next image is finished by calling grab_data_asyncgrab_data_asyncGrabDataAsyncGrabDataAsyncGrabDataAsync or grab_image_asyncgrab_image_asyncGrabImageAsyncGrabImageAsyncGrabImageAsync. If more than MaxDelayMaxDelayMaxDelayMaxDelaymaxDelay 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 MaxDelayMaxDelayMaxDelayMaxDelaymaxDelay, this control mechanism is deactivated.

To abort the grab, the operator set_framegrabber_paramset_framegrabber_paramSetFramegrabberParamSetFramegrabberParamSetFramegrabberParam 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_imageGrabImageGrabImageGrabImage or grab_datagrab_dataGrabDataGrabDataGrabData after grab_data_asyncgrab_data_asyncGrabDataAsyncGrabDataAsyncGrabDataAsync, the asynchronous grab started by grab_data_asyncgrab_data_asyncGrabDataAsyncGrabDataAsyncGrabDataAsync is aborted and a new synchronous grab is started.

Attention

For a multithreaded application all image acquisition operators (as listed in open_framegrabberopen_framegrabberOpenFramegrabberOpenFramegrabberOpenFramegrabber) are an own group in which info_framegrabberinfo_framegrabberInfoFramegrabberInfoFramegrabberInfoFramegrabber, open_framegrabberopen_framegrabberOpenFramegrabberOpenFramegrabberOpenFramegrabber, close_framegrabberclose_framegrabberCloseFramegrabberCloseFramegrabberCloseFramegrabber and close_all_framegrabbersclose_all_framegrabbersCloseAllFramegrabbersCloseAllFramegrabbersCloseAllFramegrabbers are executed exclusively.

grab_data_asyncgrab_data_asyncGrabDataAsyncGrabDataAsyncGrabDataAsync 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

ImageImageImageImageimage (output_object) image(-array) → object (byte / real / uint2)

Grabbed image data.

RegionRegionRegionRegionregion (output_object) region(-array) → object

Pre-processed image regions.

ContoursContoursContoursContourscontours (output_object) xld_cont(-array) → object

Pre-processed XLD contours.

AcqHandleAcqHandleAcqHandleAcqHandleacqHandle (input_control) framegrabber → (handle)

Handle of the acquisition device to be used.

MaxDelayMaxDelayMaxDelayMaxDelaymaxDelay (input_control) number → (real)

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

DataDataDataDatadata (output_control) string(-array) → (string / real / integer / handle)

Pre-processed control data.

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_asyncGrabDataAsyncGrabDataAsyncGrabDataAsync, the operator grab_data_asyncgrab_data_asyncGrabDataAsyncGrabDataAsyncGrabDataAsync returns the value 2 (H_MSG_TRUE). Otherwise an exception is raised.