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ISIS Application Documentation


hisharpen

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HiSharpen uses a linear frequency domain filter to remove the minor blur caused by the optical system of the HiRISE camera.

Overview Parameters Example 1

Description

HiSharpen uses a linear frequency domain filter to remove the minor blur caused by the optical system of the HiRISE camera. This blur is estimated from prelaunch measurements of the camera's point spread function (PSF) supplied by Alan Delamere of Ball Aerospace. The program accepts as input a HiRISE subimage of dimensions 2**n square. The program determines which filter (Red, BG, IR) was used for acquiring the HiRISE image and then selects the corresponding PSF and scales it to match the dimensions of the input image. First, the Fourier transforms of both the image and the PSF are calculated using the Fast Fourier Transform (FFT) algorithm. Next, the transform of the image is divided by the transform of the PSF (the Modulation Transfer Function, or MTF). The quotient is then transformed back to the spatial domain by an inverse FFT. Note that no pre-whitening or other noise suppression is done by HiSharpen. Random noise and pixel-to-pixel variations will be accentuated by HiSharpen unless steps have been taken to reduce the noise in the input image prior to sharpening. Note also that the FFT algorithm assumes that the input image is periodic, i.e. the left side of the image is repeated when the right edge of the image is reached. HiSharpen may therefore produce severe ringing in input images with low spatial frequency variations.

Categories


History

Paul Geisser2008-10-07 Original Version
Steven Lambright2008-10-07 Converted to Isis 3

Parameter Groups

Files

Name Description
FROM Input file
PSF Input file
TO
CLEANUP
X

Files: FROM


Description

Type cube
File Mode input
Close Window
X

Files: PSF


Description

Type cube
File Mode input
Internal Default Automatic
Close Window
X

Files: TO


Description

Type cube
File Mode output
Pixel Type real
Filter *.cub
Close Window
X

Files: CLEANUP


Description

Type boolean
Default true
Filter *.cub
Close Window

Example 1

Typical Run (256x256 input)

Description

This is hisharpen being run on a cropped version of a hirise cube, the cropped area has dimensions of 256 by 256.

Command Line

hisharpen from=PSP_008530_1560_IR10_0.cub to=PSP_008530_1560_IR10_0.sharp.cub
FROM and TO are the only required parameters

GUI Screenshot

Graphical Interface

Example Gui

Screenshot of GUI for this run of the program

Input Image

Input image

Input image for this program

Parameter Name: FROM

This is the input image to be sharpened

Output Image

Output image showing results of this program

Output image for this program

Parameter Name: TO

This is the sharpened output image.