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

IPSDKIPLFILTERING_API GradientXYImg	ipsdk::imaproc::filter::sobelGradient2dImg (const image::ImageConstPtr &pInImg)
	wrapper function for Sobel filter used to compute gradient on a 2d image More...

IPSDKIPLFILTERING_API GradientXYImg	ipsdk::imaproc::filter::sobelGradient2dImg (const image::ImageConstPtr &pInImg, const ipsdk::eSobelKernelType &kernelType, const bool bNormalize)
	wrapper function for Sobel filter used to compute gradient on a 2d image More...

IPSDKIPLFILTERING_API void	ipsdk::imaproc::filter::sobelGradient2dImg (const image::ImageConstPtr &pInImg, const ipsdk::eSobelKernelType &kernelType, const bool bNormalize, const image::ImagePtr &pOutOptGradXImg, const image::ImagePtr &pOutOptGradYImg)
	wrapper function for Sobel filter used to compute gradient on a 2d image More...

IPSDKIPLFILTERING_API image::ImagePtr	ipsdk::imaproc::filter::sobelXGradient2dImg (const image::ImageConstPtr &pInImg)
	wrapper function for Sobel filter used to compute gradient on a 2d image More...

IPSDKIPLFILTERING_API image::ImagePtr	ipsdk::imaproc::filter::sobelXGradient2dImg (const image::ImageConstPtr &pInImg, const ipsdk::eSobelKernelType &kernelType, const bool bNormalize)
	wrapper function for Sobel filter used to compute gradient on a 2d image More...

IPSDKIPLFILTERING_API void	ipsdk::imaproc::filter::sobelXGradient2dImg (const image::ImageConstPtr &pInImg, const ipsdk::eSobelKernelType &kernelType, const bool bNormalize, const image::ImagePtr &pOutXGradImg)
	wrapper function for Sobel filter used to compute gradient on a 2d image More...

IPSDKIPLFILTERING_API image::ImagePtr	ipsdk::imaproc::filter::sobelYGradient2dImg (const image::ImageConstPtr &pInImg)
	wrapper function for Sobel filter used to compute gradient on a 2d image More...

IPSDKIPLFILTERING_API image::ImagePtr	ipsdk::imaproc::filter::sobelYGradient2dImg (const image::ImageConstPtr &pInImg, const ipsdk::eSobelKernelType &kernelType, const bool bNormalize)
	wrapper function for Sobel filter used to compute gradient on a 2d image More...

IPSDKIPLFILTERING_API void	ipsdk::imaproc::filter::sobelYGradient2dImg (const image::ImageConstPtr &pInImg, const ipsdk::eSobelKernelType &kernelType, const bool bNormalize, const image::ImagePtr &pOutYGradImg)
	wrapper function for Sobel filter used to compute gradient on a 2d image More...

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

Attributes description

Attribute description for algorithm :

Name	ToolTip	Default Initializer
ipsdk::imaproc::attr::InImg	[Input] image for processing operation	X
ipsdk::imaproc::attr::InOptSobelKernelType	[Input Optional] kernel type for Sobel gradient filter	X
ipsdk::imaproc::attr::InOptNormalizeSobelKernel	[Input Optional] boolean flag indicating whether kernel use for Sobel gradient filtering has to be normalized or not	X
ipsdk::imaproc::attr::OutOptGradXImg	[Output Optional] image associated to X component of gradient computation	promoteUnary (_pOutOptGradXImg, _pInImg, ipsdk::imaproc::ePromoteUnaryType::ePUT_UpperSigned)
ipsdk::imaproc::attr::OutOptGradYImg	[Output Optional] image associated to Y component of gradient computation	promoteUnary (_pOutOptGradYImg, _pInImg, ipsdk::imaproc::ePromoteUnaryType::ePUT_UpperSigned)

Global Rule description

Global rule description for algorithm :
((ipsdk::processor::isSet (_pOutOptGradXImg) ||
  ipsdk::processor::isSet (_pOutOptGradYImg)) &&
(ipsdk::processor::ifIsSet (_pOutOptGradXImg,
   ipsdk::imaproc::matchSize (_pInImg,_pOutOptGradXImg))) &&
(ipsdk::processor::ifIsSet (_pOutOptGradYImg,
   ipsdk::imaproc::matchSize (_pInImg,_pOutOptGradYImg))))

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

Associated library

IPSDKIPLFiltering

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);

See also: SobelGradient2dImgLvl1

Function Documentation

◆ sobelGradient2dImg() [1/3]

IPSDKIPLFILTERING_API GradientXYImg ipsdk::imaproc::filter::sobelGradient2dImg ( const image::ImageConstPtr & pInImg )