Download Astronomical Images Compression using Wavelets

Astronomical Images Compression using
Wavelets
CHARITY WILLIAMS , Virginia State University
SARAH CONSTANTINE, South Carolina State University
TIFFANY YOUNG, Medgar Evers College
DR. KUZMAN ADZIEVSKI, TEAM LEADER
South Carolina State University, URIA 2002
INTRODUCTION
• What are wavelets
• Astronomical Image Compression
• Software used for image analysis
WAVELETS
• Wavelets are functions that satisfy certain
mathematical requirements and are used in
representing data or other functions.
• Wavelets are generated from one single
function or mother function.
• Two main wavelets-Haar
-Daubechies
HAAR
• The Haar wavelet is the simplest type of wavelet.
It is generated over the domain [0,1], where it is
equal to 1 from [0,1/2] and -1 from [1/2,1].
DAUBECHIES
• Wavelet that is more complicated than the
Haar wavelet.
FAWAV
• Fawav is a software used to compress
images.
• The purpose of image compression is to
reduce the volume of a particular image in
order to store or denoise.
• Compression can be obtained in Fawav by
altering the threshold, using Haar wavelets,
Coiflets, or Daubechie wavelets.
CHARITY.JPG
IRAF
• IRAF- Image Reduction Analysis Facility
• Applications- Compression/Decompression
Histogram Plot/Viewing
• Unix →physics%→iraf→data→pinwheel
• Compression:
/opt/bin/fcompress –s 200 pinwheel.fits
cp pinwheel.fits pin.fits
rm pinwheel.fits
/opt/bin/fdecompress pinwheel.fits.H
• Viewing – Launch IRAF (cl)
Images→imhist →histogram(xgterm &)
→imstat (max,min,sd,…)
tv →display→image(ds9 &)
Pinwheel.fits
High compression
Pinwheel.fits
Low compression
ASTRONOMICAL IMAGE
PROCESSING
• WHAT IS A FITS
FORMAT
• FITS HEADER
• HISTOGRAM
• IMAGE ANALYSIS
AIP CON’T
• FITS (Flexible Image Transport System)
evolved in 1980’s
• Header Files contains additional information
about the image. ex: who took the exposure,
and the type and size of telescope used.
• The histogram shows the different pixel
values found in the image and its frequency
AIP CON’T
• Cannot view the compressed (Pinwheel.fits.H)
• The image analysis consist of the following:
• Minimum pixel value – bottom range of the pixel
values
• Maximum – top range of the pixel value
• Mean – slightly greater than the sky pixel value
• Median – MN rows & columns/2 in the image has
•
greater pixel value
Mode – most frequent pixel value seen in an image
AIP CON’T
• Standard Deviation – is the measure of the
distribution of pixel values from the mean value
of the image
• These variables (mode, mean, median etc)
which are used in the analysis tells us how much
the decompressed image deviates from the
original image.
• Our main goal is to compressed an image without
loosing any valuable information.
AIPT CON’T
• Cross Histogram → allows you to compare the
relationship between the pixel values in two
separate images.
• Distance Tool → Measures the precise distance
and angle between star images.
Problems we will overcome!
• Finding compatible images to use for
each of the software.
• Compressing.
• Analyzing statistics.
Where there is no STRUGGLE there is no PROGRESS!
Acknowledgements
Dr. Adzievski
Dr. Walter
Dr. Smith