xGradImg,yGradImg =	sobelGradient2dImg (inImg)
xGradImg,yGradImg =	sobelGradient2dImg (inImg,kernelType,bNormalize)
image =	sobelXGradient2dImg (inImg)
image =	sobelXGradient2dImg (inImg,kernelType,bNormalize)
image =	sobelYGradient2dImg (inImg)
image =	sobelYGradient2dImg (inImg,kernelType,bNormalize)

Detailed Description

Compute X and Y gradients of an input image convolving it with 2d Sobel kernels.

2d Sobel kernels are separable, they can be decomposed as the product of a row vector and a column vector. X gradient kernel equals to the product of the smoothing (column) vector with the derivative (row) vector, while Y gradient kernel equals to the product of the derivative (column) vector with the smoothing (row) vector. Depending on the value of parameter $InOptSobelKernelType$ (default value: eSKT_SobelHalfKnlSz1), smoothing and derivative vectors equal to:

$V_{smoothing}=\begin{bmatrix} 1 & 2 & 1 \end{bmatrix}$ , $V_{deriv}=\begin{bmatrix} -1 & 0 & 1 \end{bmatrix}$ if equals to eSKT_SobelHalfKnlSz1
$V_{smoothing}=\begin{bmatrix} 3 & 10 & 3 \end{bmatrix}$ , $V_{deriv}=\begin{bmatrix} -1 & 0 & 1 \end{bmatrix}$ if equals to eSKT_ScharrHalfKnlSz1
$V_{smoothing}=\begin{bmatrix} 1 & 4 & 6 & 4 & 1 \end{bmatrix}$ , $V_{deriv}=\begin{bmatrix} -1 & -2 & 0 & 2 & 1 \end{bmatrix}$ if equals to eSKT_SobelHalfKnlSz2
$V_{smoothing}=\begin{bmatrix} 1 & 6 & 15 & 20 & 15 & 6 & 1 \end{bmatrix}$ , $V_{deriv}=\begin{bmatrix} -1 & -4 & -5 & 0 & 5 & 4 & 1 \end{bmatrix}$ if equals to eSKT_SobelHalfKnlSz3

has the default value . When the user sets this parameter to the value , only the smoothing part of the 2d kernel is normalized.

To handle image borders, a mirror extrapolation is used (see Border policy for more details).

Here is an example of a Sobel gradient applied to an 8-bits grey levels input image with default parameters used:

See also: https://en.wikipedia.org/wiki/Sobel_operator

Example of Python code :

Example imports

import PyIPSDK

import PyIPSDK.IPSDKIPLFiltering as filter

Code Example

    # opening of input images
    inImg = PyIPSDK.loadTiffImageFile(inputImgPath)
    
    # Sobel gradient filter 2d computation
    outGxImg,  outGyImg = filter.sobelGradient2dImg(inImg)

Example of C++ code :

Example informations

Header file

#include <IPSDKIPL/IPSDKIPLFiltering/Processor/SobelGradient2dImg/SobelGradient2dImg.h>

Code Example

    // opening input image from TIFF file
    ImagePtr pInImg = loadTiffImageFile(inputImgPath);
    // applying Sobel gradient to input image
    GradientXYImg gradientXY = sobelGradient2dImg(pInImg);