grab_image_startT_grab_image_startGrabImageStartGrabImageStartgrab_image_start (Operator)

Name

grab_image_startT_grab_image_startGrabImageStartGrabImageStartgrab_image_start — Start an asynchronous grab from the specified image acquisition device.

Signature

Description

The operator grab_image_startgrab_image_startGrabImageStartGrabImageStartgrab_image_start starts the asynchronous grab of an image via the image acquisition device specified by AcqHandleAcqHandleAcqHandleacqHandleacq_handle. 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_framegrabberOpenFramegrabberOpenFramegrabberopen_framegrabber and set_framegrabber_paramset_framegrabber_paramSetFramegrabberParamSetFramegrabberParamset_framegrabber_param.

The grab is finished via grab_image_asyncgrab_image_asyncGrabImageAsyncGrabImageAsyncgrab_image_async or grab_data_asyncgrab_data_asyncGrabDataAsyncGrabDataAsyncgrab_data_async. The MaxDelayMaxDelayMaxDelaymaxDelaymax_delay parameter is obsolete and does not effect the new asynchronous grab. Note that you can check for a too old image by using the MaxDelayMaxDelayMaxDelaymaxDelaymax_delay parameter of the operator grab_image_asyncgrab_image_asyncGrabImageAsyncGrabImageAsyncgrab_image_async or grab_data_asyncgrab_data_asyncGrabDataAsyncGrabDataAsyncgrab_data_async, respectively.

Please note that the operator grab_image_startgrab_image_startGrabImageStartGrabImageStartgrab_image_start makes sense only when used together with grab_image_asyncgrab_image_asyncGrabImageAsyncGrabImageAsyncgrab_image_async or grab_data_asyncgrab_data_asyncGrabDataAsyncGrabDataAsyncgrab_data_async. If you call the operators grab_imagegrab_imageGrabImageGrabImagegrab_image or grab_datagrab_dataGrabDataGrabDatagrab_data instead, the asynchronous grab started by grab_image_startgrab_image_startGrabImageStartGrabImageStartgrab_image_start is aborted and a new synchronous grab is started.

To abort the grab, the operator set_framegrabber_paramset_framegrabber_paramSetFramegrabberParamSetFramegrabberParamset_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.

Attention

For a multithreaded application, info_framegrabberinfo_framegrabberInfoFramegrabberInfoFramegrabberinfo_framegrabber, open_framegrabberopen_framegrabberOpenFramegrabberOpenFramegrabberopen_framegrabber, and close_framegrabberclose_framegrabberCloseFramegrabberCloseFramegrabberclose_framegrabber are executed exclusively.

grab_image_startgrab_image_startGrabImageStartGrabImageStartgrab_image_start 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 named AcqName.
open_framegrabber('AcqName', 1, 1, 0, 0, 0, 0, 'default', -1, 'default', \
                  -1.0, 'default', 'default', 'default', -1, -1, AcqHandle)
* Start asynchronous grabbing.
grab_image_start(AcqHandle, -1)
* Run acquisition loop.
while (true)
    * Get image, start next grab.
    grab_image_async(Image, AcqHandle, -1.0)
    * Next: Do something with the grabbed image.
endwhile
close_framegrabber(AcqHandle)

Result

If the image acquisition device is open and supports asynchronous grabbing the operator grab_image_startgrab_image_startGrabImageStartGrabImageStartgrab_image_start returns the value 2 ( H_MSG_TRUE) . Otherwise an exception is raised.

Possible Predecessors

open_framegrabberopen_framegrabberOpenFramegrabberOpenFramegrabberopen_framegrabber, set_framegrabber_paramset_framegrabber_paramSetFramegrabberParamSetFramegrabberParamset_framegrabber_param

Possible Successors

grab_image_asyncgrab_image_asyncGrabImageAsyncGrabImageAsyncgrab_image_async, grab_data_asyncgrab_data_asyncGrabDataAsyncGrabDataAsyncgrab_data_async, set_framegrabber_paramset_framegrabber_paramSetFramegrabberParamSetFramegrabberParamset_framegrabber_param, close_framegrabberclose_framegrabberCloseFramegrabberCloseFramegrabberclose_framegrabber

See also

open_framegrabberopen_framegrabberOpenFramegrabberOpenFramegrabberopen_framegrabber, info_framegrabberinfo_framegrabberInfoFramegrabberInfoFramegrabberinfo_framegrabber, set_framegrabber_paramset_framegrabber_paramSetFramegrabberParamSetFramegrabberParamset_framegrabber_param

Module

Foundation