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image.hanning - Function

	Package	general
	Module	images
	Tool	image

Convolve one axis of image with a Hanning kernel

Synopsis
hanning(outfile, region, mask, axis, drop, overwrite, async)

Arguments

outfile	in	Output image file name
		Allowed:	String
		Default:	unset
region	in	Region of interest
		Allowed:	Region tool
		Default:	Whole image
mask	in	OTF mask
		Allowed:	Boolean LEL expression or mask region
		Default:	None
axis	in	Axis to convolve
		Allowed:	Positive integer
		Default:	Spectral axis if there is one
drop	in	Drop every other pixel on output ?
		Allowed:	Bool
		Default:	T
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 performs Hanning convolution ( z[i] = 0.25*y[i - 1] + 0.5*y[i] + 0.25*y[i + 1]) of one axis of an image. The convolution is done in the image domain (i.e., not with an FFT). You can optionally drop every other pixel on output. If you do this, the first output pixel is centred on the second input pixel.

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.

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 convolve.

Example

- dowait := T
- im := image('x')
- im2 := im.hanning(outfile='x.hann')

This would Hanning smooth the spectral axis of the image associated with the image tool im, if there is one. Every other pixel on the convolution axis is dropped on output, by default.