grab_image_startT_grab_image_startGrabImageStartGrabImageStartgrab_image_start (算子)

名称

grab_image_startT_grab_image_startGrabImageStartGrabImageStartgrab_image_start — 从指定的图像采集设备启动异步抓取。

签名

grab_image_start( : : AcqHandle, MaxDelay : )

描述

算子 grab_image_startgrab_image_startGrabImageStartGrabImageStartGrabImageStartgrab_image_start starts the asynchronous grab of an image via the image acquisition device specified by AcqHandleAcqHandleAcqHandleAcqHandleacqHandleacq_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_framegrabberOpenFramegrabberOpenFramegrabberOpenFramegrabberopen_framegrabber and set_framegrabber_paramset_framegrabber_paramSetFramegrabberParamSetFramegrabberParamSetFramegrabberParamset_framegrabber_param。

The grab is finished via grab_image_asyncgrab_image_asyncGrabImageAsyncGrabImageAsyncGrabImageAsyncgrab_image_async or grab_data_asyncgrab_data_asyncGrabDataAsyncGrabDataAsyncGrabDataAsyncgrab_data_async。The MaxDelayMaxDelayMaxDelayMaxDelaymaxDelaymax_delay parameter is obsolete and does not effect the new asynchronous grab.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 MaxDelayMaxDelayMaxDelayMaxDelaymaxDelaymax_delay parameter of the operator grab_image_asyncgrab_image_asyncGrabImageAsyncGrabImageAsyncGrabImageAsyncgrab_image_async or grab_data_asyncgrab_data_asyncGrabDataAsyncGrabDataAsyncGrabDataAsyncgrab_data_async, respectively.

Please note that the operator grab_image_startgrab_image_startGrabImageStartGrabImageStartGrabImageStartgrab_image_start makes sense only when used together with grab_image_asyncgrab_image_asyncGrabImageAsyncGrabImageAsyncGrabImageAsyncgrab_image_async or grab_data_asyncgrab_data_asyncGrabDataAsyncGrabDataAsyncGrabDataAsyncgrab_data_async。If you call the operators grab_imagegrab_imageGrabImageGrabImageGrabImagegrab_image or grab_datagrab_dataGrabDataGrabDataGrabDatagrab_data instead, the asynchronous grab started by grab_image_startgrab_image_startGrabImageStartGrabImageStartGrabImageStartgrab_image_start is aborted and a new synchronous grab is started.

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.

注意

For a multithreaded application, info_framegrabberinfo_framegrabberInfoFramegrabberInfoFramegrabberInfoFramegrabberinfo_framegrabber, open_framegrabberopen_framegrabberOpenFramegrabberOpenFramegrabberOpenFramegrabberopen_framegrabber, and close_framegrabberclose_framegrabberCloseFramegrabberCloseFramegrabberCloseFramegrabberclose_framegrabber are executed exclusively.

grab_image_startgrab_image_startGrabImageStartGrabImageStartGrabImageStartgrab_image_start runs in parallel with all non-exclusive operators inside and outside of this group.

执行信息

多线程类型：可重入（与非独占算子并行运行）。
多线程作用域：全局（可从任何线程调用）。
未采用并行化处理。

参数

AcqHandleAcqHandleAcqHandleAcqHandleacqHandleacq_handle (输入控制) framegrabber → (handle)

Handle of the acquisition device to be used.

MaxDelayMaxDelayMaxDelayMaxDelaymaxDelaymax_delay (输入控制) number → (real)

This parameter is obsolete and has no effect.

默认值： -1.0

建议值： -1.0, 20.0, 33.3, 40.0, 66.6, 80.0, 99.9

示例（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)

结果

If the image acquisition device is open and supports asynchronous grabbing the operator grab_image_startgrab_image_startGrabImageStartGrabImageStartGrabImageStartgrab_image_start 返回值 2 ( H_MSG_TRUE )。否则将抛出异常。

可能的前趋

open_framegrabberopen_framegrabberOpenFramegrabberOpenFramegrabberOpenFramegrabberopen_framegrabber, set_framegrabber_paramset_framegrabber_paramSetFramegrabberParamSetFramegrabberParamSetFramegrabberParamset_framegrabber_param

可能的后继

grab_image_asyncgrab_image_asyncGrabImageAsyncGrabImageAsyncGrabImageAsyncgrab_image_async, grab_data_asyncgrab_data_asyncGrabDataAsyncGrabDataAsyncGrabDataAsyncgrab_data_async, set_framegrabber_paramset_framegrabber_paramSetFramegrabberParamSetFramegrabberParamSetFramegrabberParamset_framegrabber_param, close_framegrabberclose_framegrabberCloseFramegrabberCloseFramegrabberCloseFramegrabberclose_framegrabber

另见

open_framegrabberopen_framegrabberOpenFramegrabberOpenFramegrabberOpenFramegrabberopen_framegrabber, info_framegrabberinfo_framegrabberInfoFramegrabberInfoFramegrabberInfoFramegrabberinfo_framegrabber, set_framegrabber_paramset_framegrabber_paramSetFramegrabberParamSetFramegrabberParamSetFramegrabberParamset_framegrabber_param

模块

基础

算子