Start an asynchronous grab of an image from the specified frame grabber.
The operator ::grab_image_start starts an asynchronous grab of an image via the frame grabber specified by FGHandle. The desired operational mode of the frame grabber as well as a suitable image area can be adjusted via the operator ::open_framegrabber. Additional (frame grabber specific) settings might be possible via ::set_framegrabber_param. The grab is finished via ::grab_image, ::grab_image_async, ::grab_region, or ::grab_region_async. If one of those operators is called more than MaxDelay ms later, a new image is grabbed (the asynchronously grabbed image is considered as to old). If a negative value is assigned to MaxDelay this control mechanism is deactivated.
|
FGHandle (input_control) |
framegrabber -> HTuple.long |
| Handle of the frame grabber to be used. | |
|
MaxDelay (input_control) |
number -> HTuple.double |
| Maximum tolerated delay between the start of the asynchronous grab and the delivery of the image [ms]. | |
| Default value: -1.0 | |
| Suggested values: 20.0, 33.3, 40.0, 66.6, 80.0, 99.9 | |
/* Select a suitable frame grabber FgName */
info_framegrabber(FgName,"ports",&Information,&Val) ;
/* Choose the port P and the input line L your camera is connected to */
open_framegrabber(FgName,1,1,0,0,0,0,"default",-1,"default",-1.0,
"default","default","default",P,L,&FgHandle) ;
grab_image(&Img,FgHandle) ;
/* Start next grab */
grab_image_start(FgHandle,-1.0) ;
/* Process Img ... */
/* Finish asynchronous grab */
grab_image(Img,FgHandle) ;
close_framegrabber(FgHandle) ;
If the frame grabber is open and supports asynchronous grabbing the operator ::grab_image_start returns the value H_MSG_TRUE. Otherwise an exception handling is raised.
::grab_image, ::grab_region, ::grab_image_async, ::grab_region_async, ::close_framegrabber
::open_framegrabber, ::info_framegrabber, ::set_framegrabber_param
Image / region / XLD management
