Grab of an image from the specified frame grabber and start of the asynchronous grab of the next image.
The operator grab_image_async grabs an image via the frame grabber specified by FGHandle and starts the asynchronous grab of the next image. 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 of the next image is finished by calling grab_image_async or grab_region_async. If more than MaxDelay ms have passed since the asynchronous grab was started, a new image is grabbed (the asynchronously grabbed image is considered as too old). If a negative value is assigned to MaxDelay this control mechanism is deactivated.
Please note that if you call the operators grab_image or grab_region after grab_image_async, the asynchronous grab started by grab_image_async is aborted and a new image is grabbed (and waited for).
|
Image (output_object) |
image -> object : byte / int2 |
| Grabbed image. | |
|
FGHandle (input_control) |
framegrabber -> integer |
| Handle of the frame grabber to be used. | |
|
MaxDelay (input_control) |
number -> real |
| Maximum tolerated delay beteween 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 | |
// Select a suitable frame grabber FgName
open_framegrabber(FgName,1,1,0,0,0,0,'default',-1,'default',-1.0,
'default','default','default',-1,-1,FgHandle)
// grab image + start next grab
grab_image_async(Img1,FgHandle,-1.0)
// Process Img1 ...
// Finish asynchronous grab + start next grab
grab_image_async(Img2,FgHandle,-1.0)
close_framegrabber(FgHandle)If the frame grabber is open and supports asynchronous grabbing the operator grab_image_async returns the value 2 (H_MSG_TRUE). Otherwise an exception handling is raised.
grab_image_async is reentrant and processed without parallelization.
grab_image_async, grab_region_async, close_framegrabber
grab_image_start, open_framegrabber, info_framegrabber, set_framegrabber_param
Image / region / XLD management
