LAPLACE - Performs a Laplacian convolution as an edge detector in a two-dimensional NDF

Description:

This routine calculates the Laplacian of the supplied two-dimensional NDF , and subtracts it from the original array to create the output NDF. The subtractions can be done a specified integer number of times. This operation can be approximated by a convolution with the kernel:

$\begin{array}{ccc} N & -N & -N \\ N & +8N & -N \\ N & -N & -N \end{array}$

where N is the integer number of times the Laplacian is subtracted. This convolution is used as a uni-directional edge detector. Areas where the input data array is flat become zero in the output data array.

Usage:

laplace in [number] out [title]

Parameters:

IN = NDF (Read)

Input NDF.

NUMBER = _INTEGER (Read)

Number of Laplacians to remove. [1]

OUT = NDF (Write)

Output NDF.

TITLE = LITERAL (Read)

The title for the output NDF. A null value will cause the title of the NDF supplied for parameter IN to be used instead. [!]

Examples:

laplace a 10 b

This subtracts ten Laplacians from the NDF called a, to make the NDF called b. NDF b inherits its title from a.

Related Applications

KAPPA: SHADOW, MEDIAN; FIGARO: ICONV3.

Implementation Status:

• This routine correctly processes the WCS, AXIS, DATA, and VARIANCE components of an NDF data structure. QUALITY is propagated.

• Processing of bad pixels and automatic quality masking are supported.

• All non-complex numeric data types can be handled.