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image.convolve - Function

	Package	general
	Module	images
	Tool	image

Convolve image with a Glish array or another image

Synopsis
convolve(outfile, kernel, scale, region, mask, overwrite, async)

Arguments

outfile	in	Output image file name
		Allowed:	String
		Default:	unset
kernel	in	Convolution kernel - array or image filename
		Allowed:	Numeric Glish array or string
scale	in	Scale factor
		Allowed:	Float
		Default:	Autoscale
region	in	Region of interest
		Allowed:	Region tool
		Default:	Whole image
mask	in	OTF mask
		Allowed:	Boolean LEL expression or mask region
		Default:	None
overwrite	in	Overwrite (unprompted) pre-existing output file ?
		Allowed:	T or F
		Default:	F
async	in	Run asynchronously?
		Allowed:	Bool
		Default:	!dowait

Returns
Image tool or fail

Description

This function does Fourier-based convolution of an image file by the given kernel.

If outfile is given, the image is written to the specified disk file. If outfile is unset, the Image tool is associated with a temporary image. This temporary image may be in memory or on disk, depending on its size. When you destroy the Image tool (with the done function) this temporary image is deleted.

The kernel is provided as a multi-dimensional Glish array or as the filename of a disk-based image file. The provided kernel can have less dimensions than the image being convolved. In this case, it will be padded with degenerate axes. An error will result if the kernel has more dimensions than the image. No additional scaling of the kernel is provided yet.

The scaling of the output image is determined by the argument scale. If you leave it unset, then the kernel is normalized to unit sum. If you do not leave scale unset, then the convolution kernel will be scaled (multipled) by this value.

Masked pixels will be assigned the value 0.0 before convolution.

The output mask is the combination (logical OR) of the default input pixel mask (if any) and the OTF mask. Any other input pixel masks will not be copied. Use function maskhandler if you need to copy other masks too.

See also the other convolution functions convolve2d, sepconvolve and hanning.

Example

- dowait := T
- r1 := drm.quarter()
- im := image('pks1333-33.6cm')
- kernel := mykernel(...)                          # Your code to generate the kernel
- im2 := im.convolve(kernel=kernel, region=r1)     # Makes temporary image
-
- im3 := im.convolve (kernel=im.name(F))           # Convolve by self