/// <summary>
/// Returns Gaussian filter coefficients.
/// </summary>
/// <param name="ksize">Aperture size. It should be odd and positive.</param>
/// <param name="sigma">Gaussian standard deviation.
/// If it is non-positive, it is computed from ksize as `sigma = 0.3*((ksize-1)*0.5 - 1) + 0.8`.</param>
/// <param name="ktype">Type of filter coefficients. It can be CV_32F or CV_64F.</param>
/// <returns></returns>
public static Mat GetGaussianKernel(int ksize, double sigma, MatType? ktype = null)
{
var ktype0 = ktype.GetValueOrDefault(MatType.CV_64F);
var ret = NativeMethods.imgproc_getGaussianKernel(ksize, sigma, ktype0);
if (ret == IntPtr.Zero)
return null;
return new Mat(ret);
}
/// <summary>
/// Returns filter coefficients for computing spatial image derivatives.
/// </summary>
/// <param name="kx">Output matrix of row filter coefficients. It has the type ktype.</param>
/// <param name="ky">Output matrix of column filter coefficients. It has the type ktype.</param>
/// <param name="dx">Derivative order in respect of x.</param>
/// <param name="dy">Derivative order in respect of y.</param>
/// <param name="ksize">Aperture size. It can be CV_SCHARR, 1, 3, 5, or 7.</param>
/// <param name="normalize">Flag indicating whether to normalize (scale down) the filter coefficients or not.
/// Theoretically, the coefficients should have the denominator \f$=2^{ksize*2-dx-dy-2}\f$.
/// If you are going to filter floating-point images, you are likely to use the normalized kernels.
/// But if you compute derivatives of an 8-bit image, store the results in a 16-bit image,
/// and wish to preserve all the fractional bits, you may want to set normalize = false.</param>
/// <param name="ktype">Type of filter coefficients. It can be CV_32f or CV_64F.</param>
public static void GetDerivKernels(
OutputArray kx, OutputArray ky, int dx, int dy, int ksize,
bool normalize = false, MatType? ktype = null)
{
if (kx == null)
throw new ArgumentNullException(nameof(kx));
if (ky == null)
throw new ArgumentNullException(nameof(ky));
kx.ThrowIfNotReady();
ky.ThrowIfNotReady();
var ktype0 = ktype.GetValueOrDefault(MatType.CV_32F);
NativeMethods.imgproc_getDerivKernels(
kx.CvPtr, ky.CvPtr, dx, dy, ksize, normalize ? 1 : 0, ktype0);
kx.Fix();
ky.Fix();
}