2D Ricker wavelet filter kernel (sometimes known as a “Mexican Hat” kernel).
The Ricker wavelet, or inverted Gaussian-Laplace filter, is a bandpass filter. It smooths the data and removes slowly varying or constant structures (e.g. Background). It is useful for peak or multi-scale detection.
This kernel is derived from a normalized Gaussian function, by computing the second derivative. This results in an amplitude at the kernels center of 1. / (pi * width ** 4). The normalization is the same as for
scipy.ndimage.gaussian_laplace, except for a minus sign.
See https://github.com/astropy/astropy/pull/9445 for discussions related to renaming of this kernel.
Width of the filter kernel, defined as the standard deviation of the Gaussian function from which it is derived.
- x_sizeodd int, optional
Size in x direction of the kernel array. Default = 8 * width.
- y_sizeodd int, optional
Size in y direction of the kernel array. Default = 8 * width.
- modestr, optional
- One of the following discretization modes:
- ‘center’ (default)
Discretize model by taking the value at the center of the bin.
Discretize model by performing a bilinear interpolation between the values at the corners of the bin.
Discretize model by taking the average on an oversampled grid.
Discretize model by integrating the model over the bin.
- factornumber, optional
Factor of oversampling. Default factor = 10.