1.1.1.0 image.fft

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image.fft - Function

1.1.1 FFT the image

Description

This function fast Fourier Transforms the supplied image to the Fourier plane. Both float valued and complex valued images are supported. If the axes parameter is left unset, then the sky plane of the image (if there is one) is transformed. Otherwise, the user can specify which axes are to be transformed. Note that if a sky axis is to be transformed, both of them must be specified.

The user specifies which form is desired in the result by specifying the desired output image file name(s).

Before the FFT is performed, any masked pixels are set to values of zero. 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. The function maskhandler can be used if there is a need to copy other masks too.

Arguments


Inputs
real	Output real image file name.
	allowed:	string
	Default:
imag	Output imaginary image file name.
	allowed:	string
	Default:
amp	Output amplitude image file name.
	allowed:	string
	Default:
phase	Output phase image file name.
	allowed:	string
	Default:
axes	Specify the pixel axes that are to undergo the FFT. The default option (-1) is to transform the sky plane(s).
	allowed:	intArray
	Default:	-1
region	Region selection. See ”help par.region” for details. Default is to use the full image.
	allowed:	any
	Default:	variant
mask	The mask to be used. See ”help par.mask” for more details. The default option is none.
	allowed:	any
	Default:	variant
stretch	Stretch the mask if it is necessary and possible. See ”help par.stretch” for more details.
	allowed:	bool
	Default:	false
complex	Output complex valued image file name.
	allowed:	string
	Default:

Returns
bool

Example

"""
#
print "\t----\t fft Ex 1 \t----"
# Create a test image:
ia.maketestimage(’gc.small’, overwrite=true)
# Perform an FFT on the sky plane of the test image,
# writing out just the resulting real and amplitude images:
ia.fft(real=’r.im’, amp=’a.im’)
# Close the image tool when done:
ia.close()
# Lastly, clean up the example output files:
ia.removefile(’r.im’)
ia.removefile(’a.im’)
#
"""

Example

"""
#
print "\t----\t fft Ex 2 \t----"
# Create a zero-filled 3D test dataset and add noise to it:
ia.fromshape(’gc.small’, [64,64,128], overwrite=true)
ia.addnoise(type=’normal’, pars=[0.5, 1], zero=false)
# The following transforms only the third axis of the image.
# writing out only the amplitude and phase images.
ia.fft(amp=’amp.im’, phase=’p.im’, axes=[2])
# Close the image tool when done:
ia.close()
# Lastly, clean up the example output files:
ia.removefile(’amp.im’)
ia.removefile(’p.im’)
#
"""

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