VisionWorks Toolkit Reference

December 18, 2015 | 1.2 Release

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Detailed Description

The Median Flow Algorithm.

This algorithm estimates a median flow vector of a set of points.

The primitive uses the following identifiers:

Functions

vx_node nvxMedianFlowNode (vx_graph graph, vx_array prev_pts, vx_array next_pts, vx_array pts_fb, vx_array out, vx_bool estimate_scale, vx_bool filter_flow_by_err, vx_float32 error_fb_thresh)
 [Graph] Computes median flow. More...
 
vx_status nvxuMedianFlow (vx_context context, vx_array prev_pts, vx_array next_pts, vx_array pts_fb, vx_array out, vx_bool estimate_scale, vx_bool filter_flow_by_err, vx_float32 error_fb_thresh)
 [Immediate] Computes median flow. More...
 

Function Documentation

vx_node nvxMedianFlowNode ( vx_graph  graph,
vx_array  prev_pts,
vx_array  next_pts,
vx_array  pts_fb,
vx_array  out,
vx_bool  estimate_scale,
vx_bool  filter_flow_by_err,
vx_float32  error_fb_thresh 
)

[Graph] Computes median flow.

Parameters
[in]graphSpecifies the graph.
[in]prev_ptsSpecifies the input previous points list. Only VX_TYPE_KEYPOINT and NVX_TYPE_POINT2F item types are supported.
[in]next_ptsSpecifies the input next points list. It must have the same item type and number of items as prev_pts.
[in]pts_fb[optional] Specifies the backward points list. It must have the same item type and number of items as prev_pts.
[out]outSpecifies the output median flow. It is a one element NVX_TYPE_POINT3F array. x and y fields of the first element represent estimated displacement, z field represents estimated scale change. In case of estimation failure \( (0, 0, -1) \) is returned.
[in]estimate_scaleSpecifies whether to estimate scale change.
[in]filter_flow_by_errSpecifies whether to filter out points with a high error value.
[in]error_fb_thresh[optional] Specifies the threshold for forward-backward errors. Pass a nonpositive value to disable forward-backward filtering.
Returns
A valid node reference or an error object (use vxGetStatus).
See also
Median Flow
vx_status nvxuMedianFlow ( vx_context  context,
vx_array  prev_pts,
vx_array  next_pts,
vx_array  pts_fb,
vx_array  out,
vx_bool  estimate_scale,
vx_bool  filter_flow_by_err,
vx_float32  error_fb_thresh 
)

[Immediate] Computes median flow.

Parameters
[in]contextSpecifies the context.
[in]prev_ptsSpecifies the input previous points list. Only VX_TYPE_KEYPOINT and NVX_TYPE_POINT2F item types are supported.
[in]next_ptsSpecifies the input next points list. It must have the same item type and number of items as prev_pts.
[in]pts_fb[optional] Specifies the backward points list. It must have the same item type and number of items as prev_pts.
[out]outSpecifies the output median flow. It is a one element NVX_TYPE_POINT3F array. x and y fields of the first element represent estimated displacement, z field represents estimated scale change. In case of estimation failure \( (0, 0, -1) \) is returned.
[in]estimate_scaleSpecifies whether to estimate scale change.
[in]filter_flow_by_errSpecifies whether to filter out points with a high error value.
[in]error_fb_thresh[optional] Specifies the threshold for forward-backward errors. Pass a nonpositive value to disable forward-backward filtering.
Returns
A vx_status enumerator.
Return values
VX_SUCCESSNo errors.
VX_ERROR_INVALID_REFERENCESupplied parameters are not a valid references.
VX_ERROR_INVALID_PARAMETERSSupplied parameters are not valid.
VX_ERROR_INVALID_SCOPESupplied parameters are virtual objects, which can't be used in immediate mode.
VX_FAILUREInternal error in primitive implementation, check log for detailed information (Framework: Log).
See also
Median Flow