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image.decimate - Function

1.1.1 Remove planes from an image.


Description

This application removes planes along the specified axis of an image. It supports both float valued and complex valued images. The factor parameter represents the factor by which to reduce the number of planes.

The method parameter represents how to calculate the pixel values of the output image. A value of method=”copy” means that every factorth plane of the selected region in the input image will be directly copied to the corresponding plane in the output image. So, if one wanted to copy every third spectral plane in the input image to the output image, one would specify factor=3 and method=”copy”. If the selected region along the specified axis had 11 planes, then there would be 4 output planes which would map to planes 0, 3, 6, and 9 of the specified region of input image. A value of method=”mean” indicates that each of factor number of planes in the range starting at each factorth plane should be averaged to produce the corresponding output plane. So, if one specified factor=3 and method=”mean” along an axis of the selected region of the input image which had 11 pixels, the corresponding axis in the output image would have three pixels and the pixel values for each of those output planes would corresponding to averaging along that axis planes 0-2, 3-5, and 6-8 of the selected region of the input image. Note that the remaining planes, 9 and 10, in the selected region of the input image would be ignored because the last interval must have exactly factor number of planes in order to be included in the output image.

The coordinate system of the output image takes into account the decimation; that is, along the decimated axis, the increment of the output image is factor times that of the input image, and the reference pixel of the output image is located at pixel 1/factor times the reference pixel in the input image.

This method returns an image analysis tool which references the output image. If this tool is not desired, one should capture it anyway and then close() it immediately to free up resources.

Images with multiple beams are not supported; please convolve a multi-beam image to a single resolution before running this application.

Arguments





Inputs

outfile

Output image file name. If empty, a persistent image is not created.

allowed:

string

Default:

axis

Axis along which to remove planes.

allowed:

int

Default:

0

factor

Reduce number of planes by this factor.

allowed:

int

Default:

1

method

Method to use for calculating pixel values of output. Supported values are ”copy” or ”mean”.

allowed:

string

Default:

copy

region

Region selection. See ”help par.region” for details. Default is to use the full image.

allowed:

any

Default:

variant

mask

Mask to use. See help par.mask for more details. Default setting is none.

allowed:

string

Default:

overwrite

Overwrite (unprompted) pre-existing output file? Ignored if ”outfile” is left blank.

allowed:

bool

Default:

false

stretch

Stretch the mask if necessary and possible? See help par.stretch. Default value is False.

allowed:

bool

Default:

false

Returns
image

Example

 
# Copy verbatim every 5th plane of axis 2 of the input image  
ia.open("myim.im")  
decimated = ia.decimate("dec1.im", axis=2, factor=5, method="copy")  
# do stuff with decimated and then close it  
decimated.close()  
 
# Decimte by averaging every 7 planes of the input image along axis 2  
decimated = ia.decimate("dec2.im", axis=2, factor=7, method="mean")  
# do stuff with decimated and then close it  
decimated.close()  

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