Module: ReduceGalSet

ReduceGalSet

A module that take a set of galaxies and "reduces" the resolution by averaging pixels. To accomplish this, the input image is divided into pixel groups of size 2x2, 3x3, 4x4, etc. The values inside each group are averaged, and that value becomes a single pixel in the output image. This process can be used either to simulate subsampling of pixels when drawing galaxies, or the act of interlacing a number of perfectly spaced images.

This module start from "Big" galaxies -- those created with a special keyword. See MakeGalSet for more information.

Put another way, this module passes a rectangular filter over the image, and resamples. The resulting image will be at a lower resolution that of the input images.

Alternatively, this module can also be used to "enlarge" images. In this mode, the output image is the same size as the input image. Within each group of pixels, all of the output pixels are set to the average of those in the input.

The output of this module is a set of galaxy images, much as MakeGalSet would create. This is suitable for input to any other module that needs galaxy set inputs.

Parameters

Name Type Description

Enlarge keyword If present, use the "enlarge" mode rather than the "reduce" mode.

ReductionSize int Size of group of pixels on which to perform reduction or enlargement process.

ReductionStep int Number of pixels separating each group. If equal to ReductionSize, each group will be touching. Values large than this leave skipped pixels between groups, and values smaller than this overlaps the groups. This parameter is not used while in Enlarge mode.

Name	Type	Description
Enlarge	keyword	If present, use the "enlarge" mode rather than the "reduce" mode.
ReductionSize	int	Size of group of pixels on which to perform reduction or enlargement process.
ReductionStep	int	Number of pixels separating each group. If equal to ReductionSize, each group will be touching. Values large than this leave skipped pixels between groups, and values smaller than this overlaps the groups. This parameter is not used while in Enlarge mode.

Inputs

Name Type Description

GalSet/BiasedCount int Number of biased images.

GalSet/UnbiasedCount int Number of unbiased images.

GalSet/BigWidth int Pixel width of the images.

GalSet/BigHeight int Pixel height of the images.

GalSet/BigBiasedImages double* Array of pixel values for "big" biased images.

GalSet/BigUnbiasedImages double* Array of pixel values for "big" unbiased images.

Name	Type	Description
GalSet/BiasedCount	int	Number of biased images.
GalSet/UnbiasedCount	int	Number of unbiased images.
GalSet/BigWidth	int	Pixel width of the images.
GalSet/BigHeight	int	Pixel height of the images.
GalSet/BigBiasedImages	double*	Array of pixel values for "big" biased images.
GalSet/BigUnbiasedImages	double*	Array of pixel values for "big" unbiased images.

Outputs

Name Type Description

GalSet/Width int Pixel width of the newly created images.

GalSet/Height int Pixel height of the newly created images.

GalSet/BiasedImages double* Pixel values of the newly created biased images.

GalSet/UnbiasedImages double* Pixel values of the newly created unbiased images.

Name	Type	Description
GalSet/Width	int	Pixel width of the newly created images.
GalSet/Height	int	Pixel height of the newly created images.
GalSet/BiasedImages	double*	Pixel values of the newly created biased images.
GalSet/UnbiasedImages	double*	Pixel values of the newly created unbiased images.