The OpenVX Specification
a73e458

Provides a Canny edge detector kernel.
This function implements an edge detection algorithm similar to that described in [2]. The main components of the algorithm are:
The details of each of these steps are described below.
VX_NORM_L1
or \( \sqrt{dx^{2} + dy^{2}} \) for VX_NORM_L2
. The gradient orientation image is quantized into 4 values: 0, 45, 90, and 135 degrees. \[ \mathbf{sobel}_{x}= \begin{vmatrix} 1 & 0 & 1\\ 2 & 0 & 2\\ 1 & 0 & 1 \end{vmatrix} \]
\[ \mathbf{sobel}_{y}=transpose({sobel}_{x})= \begin{vmatrix} 1 & 2 & 1\\ 0 & 0 & 0\\ 1 & 2 & 1 \end{vmatrix} \]
\[ \mathbf{sobel}_{x}= \begin{vmatrix} 1 & 2 & 0 & 2 & 1\\ 4 & 8 & 0 & 8 & 4\\ 6 & 12 & 0 & 12 & 6\\ 4 & 8 & 0 & 8 & 4\\ 1 & 2 & 0 & 2 & 1\\ \end{vmatrix} \]
\[ \mathbf{sobel}_{y}=transpose({sobel}_{x}) \]
\[ \mathbf{sobel}_{x}= \begin{vmatrix} 1 & 4 & 5 & 0 & 5 & 4 & 1\\ 6 & 24 & 30 & 0 & 30 & 24 & 6\\ 15 & 60 & 75 & 0 & 75 & 60 & 15\\ 20 & 80 & 100 & 0 & 100 & 80 & 20\\ 15 & 60 & 75 & 0 & 75 & 60 & 15\\ 6 & 24 & 30 & 0 & 30 & 24 & 6\\ 1 & 4 & 5 & 0 & 5 & 4 & 1\\ \end{vmatrix} \]
\[ \mathbf{sobel}_{y}=transpose({sobel}_{x}) \]
Modules  
Normalization type constants.  
Functions  
vx_node VX_API_CALL  vxCannyEdgeDetectorNode (vx_graph graph, vx_image input, vx_threshold hyst, vx_int32 gradient_size, vx_enum norm_type, vx_image output) 
[Graph] Creates a Canny Edge Detection Node. More...  
vx_node VX_API_CALL vxCannyEdgeDetectorNode  (  vx_graph  graph, 
vx_image  input,  
vx_threshold  hyst,  
vx_int32  gradient_size,  
vx_enum  norm_type,  
vx_image  output  
) 
[Graph] Creates a Canny Edge Detection Node.
[in]  graph  The reference to the graph [R00338]. 
[in]  input  The input VX_DF_IMAGE_U8 image [R00339]. 
[in]  hyst  The double threshold for hysteresis [R00340]. The threshold data_type shall be either VX_TYPE_UINT8 or VX_TYPE_INT16 [R00341]. The VX_THRESHOLD_TRUE_VALUE and VX_THRESHOLD_FALSE_VALUE of vx_threshold are ignored. 
[in]  gradient_size  The size of the Sobel filter window, must support at least 3, 5, and 7 [R00342]. 
[in]  norm_type  A flag indicating the norm used to compute the gradient, VX_NORM_L1 or VX_NORM_L2 [R00343]. 
[out]  output  The output image in VX_DF_IMAGE_U8 format with values either 0 or 255 [R00344]. 
vx_node
. vx_node  A node reference. Any possible errors preventing a successful creation should be checked using vxGetStatus 