non-display-based interface class
An interface to Van-Duc's Canny code. No display is involved. The Canny has two major phases: 1) detect step edgels, 2)Follow contours and construct a topological network. Each phase has a number of parameters which are defined as follows. Step Detection:
- float contourFactor, junctionFactor: Scale factors for determining the gradient threshold. Nominally 1.0. contourFactor is in effect for edgels on contours (boundaries). junctionFactor is in effect during the extension of contours at endpoints. To extend contours aggressively, use a low value of junctionFactor, i.e., .5.
- float noiseThreshold: A weighting factor that determines the relative proportion of sensor noise level and texture noise level as measured in a ROI in the center of the image. The nominal value of -.5 gives equal weight to both. If the value is positive, then a default noise threshold of 1.0 is assigned.
- float filterFactor: An overall scale factor for determining gradient threshold. Nominally 2.0.
- bool junctionp: If true, then recover junctions by extending contours. Nominally true.
- Contour Following:
- float hysteresisFactor: A scale factor which is multiplied by the image noise level to determine the minimum gradient threshold in following an edgel contour. Nominally 2.0.
- int minLength: The minimum length contour to constructed.
- float minJump: A scale factor which is multiplied by the image noise level to determine the gradient threshold at a junction. Nominally 1.0.
- float maxGap: The width of a gap which can be crossed in forming a junction with another edgel contour. Nominally sqrt(5) = 2.24.
- bool spacingp: If true, then equalize the sub-pixel locations of each edgel by averaging the adjacent left a right neighbor locations. Nominally true.
- bool borderp: If true, insert virtual contours at the border to close regions. Nominally false.
- Author:
- Jane S. Liu - 3/27/95 GE Corporate Research and Development
Modifications
JLM - May 1997
Added extra interface for parameters not initially
provided by Jane.These parameters are needed to get
satisfactory boundary closure. Also expanded comments.
JLM - November 1997
Moved most parameters up to gevd_detectorParams in
order to unify the use of parameters.
Definition in file gevd_detector.h.
