Halcon Interface > Operators > grab

This operator is used to access the binary nodes of the NxLib API Tree.

Parameters

grab_data (Image, Region, Contours, AcqHandle, Data)

Parameter	Description
Image	Variable where the retrieved image will be stored. Note: If 'grab_data_items' contains multiple items, this will be a tuple of images.
Region	Region which describes the valid 3D points. Note: If 'grab_data_items' contains multiple items, this will be a tuple of regions.
Contours	Not used.
AcqHandle	An acquisition handle obtained via 'open_framegrabber'.
Data	Not used.

Dependencies

All dependencies can be manipulated with 'set_framegraber_param'.

Parameter

Description

grab_data_items

Contains the list of binary nodes which will be returned in the Image value.

Depending on the type of the acquisition handle following binary nodes can be accessed:

	Binary node	Image type
'Stereo'	Images/Raw/Left, Images/Raw/Right	1 channel / Byte
	Images/Rectified/Left, Images/Rectified/Right	1 channel / Byte
	Images/WithOverlay/Left, Images/WithOverlay/Right	3 channel / Byte
	Images/DisparityMap	1 channel / Int2
	Images/PointMap	3 channel / Real
'Monocular'	Images/Raw	1 channel / Byte
	Images/Rectified	1 channel / Byte
	Images/WithOverlay	3 channel / Byte
'Item' (referring to root)	Images/RenderPointMap	3 channel / Real
	Images/RenderPointMapTexture	4 channel / Byte
	Images/RenderView	3 channel / Byte

auto_grab_data

If 'auto_grab_data' is set, 'grab_data' will also automatically capture a new image and execute all necessary commands to generate the binary nodes listed in 'grab_data_items'.

Binary node	Executed commands
Images/Raw/Left, Images/Raw/Right	cmdCapture
Images/Rectified/Left, Images/Rectified/Right	cmdCapture, cmdRectifiyImages
Images/DisparityMap	cmdCapture, cmdComputeDisparityMap
Images/PointMap	cmdCapture, cmdComputeDisparityMap, cmdComputePointMap
Images/Raw	cmdCapture
Images/Rectified	cmdCapture, cmdRectifiyImages
Images/RenderPointMap	cmdCapture, cmdComputeDisparityMap, cmdRenderPointMap
Images/RenderPointMapTexture	cmdCapture, cmdComputeDisparityMap, cmdRenderPointMap
Images/RenderView	cmdCapture, cmdComputeDisparityMap, cmdRenderView

replace_nans

All internal binary fields use the NaN ("Not a number") value of the IEEE floating point format to indicate that a certain point is invalid (i.e. not triangulated). Unfortunately NaN values within images cause various problems within Halcon, therefore by stetting this flag to 'true', 'grab_data' replaces NaN values within floating point images with 0.

generate_regions

By deactivating this flag, 'grab_data' no longer delivers the Region value. This can be used to save computation time.

Note: All automaticallly executed commands will be run without parameters.

Example

* Open default stereo camera
open_framegrabber('Ensenso-NxLib', 0, 0, 0, 0, 0, 0, 'default', 0, 'Raw', -1, 'false', 'Stereo', '', 0, 0, AcqHandle)

* Set 'grab_data_items'
* 'grab_data_items' is by default 'Images/PointMap' for Stereo handles
set_framegrabber_param (AcqHandle, 'grab_data_items', ['Images/DisparityMap','Images/PointMap'])

* Grab images with 'auto_grab_data' on
grab_data (Image, Region, Contours, AcqHandle, Data)

*without 'auto_grab_data' following commands would be needed for the same result:
set_framegrabber_param (AcqHandle, 'auto_grab_data', 'false')
open_framegrabber('Ensenso-NxLib', 0, 0, 0, 0, 0, 0, 'default', 0, 'Raw', -1, 'false', 'Item', '/', 0, 0, RootHandle)
set_framegrabber_param (RootHandle, 'do_execute', 'Capture')
set_framegrabber_param (RootHandle, 'do_execute', 'ComputeDisparityMap')
set_framegrabber_param (RootHandle, 'do_execute', 'ComputePointMap')
grab_data (Image, Region, Contours, AcqHandle, Data)