DIP Realized by IDL Author: Ying Li Course: computer for imaging science.
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20-Dec-2015 -
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Transcript of DIP Realized by IDL Author: Ying Li Course: computer for imaging science.
Program Overview
My project has 5 modules: 1. Zooming module 2. Filter module 3. Fourier transform module 4. Histogram module 5. Motion blur and restoration module
Zooming Module
Color table Keep track of the button status Restrict the rectangle from going
outside of the image Erase old rectangles
Color Table
I want to display a gray level image with a red region of interest displayed on it. So I need a color table of my own.
I set a flag variable to keep track of the mouse buttons’ status. So user can only drag the red rectangle with the mouse button pressed down.
The program calculated carefully to prevent the red rectangle from going outside of the image.
Erase old rectangle
In order for the red rectangle to go with the mouse, the program must erase the old rectangle and draw a new rectangle at the new position.
To do this I use a hidden draw widget to display the image at exactly the same position, and erase old rectangle by copy data from the hidden window.
Filter Module
In this module I realized four kind of filters:
Ideal low pass filter Ideal high pass filter Ideal band pass filter Butterworth low pass filter
Butterworth Filter:
We know because of the the sharp edge of the ideal filters, there will be some oscillation on the output signal of ideal filters.
So, we want a kind of filter whose edges go down slowly. Butterworth filter was introduced.
This is the equation of a 1-D Butterworth filter:
Here N is the order of the Butterworth filter and c is the frequency cutoff
Nc
B2)/(1
1|)(|
Motion Blur Restoration
Using a Inverse Filter to deconvolve the point spread function
Using convolve method to get ride of the blur coursed by the motion of the detector or the object
Inverse Filter
Before image restoration can be accomplished, the PSF of the blurring function(that is the system transfer function of the degrading system) must be known. Actually most system that course the degrading of images are linear shift invariant system.
Solve by inverse filter:
Here if the noise is very small and can be neglected. Then we can restore the image by a reverse filter:
),(),(),(),( NFHG
HGF /
Convolution Method:
We still have some other ways to restore a motion blurred image. The motion blur is coursed by the moving of the detector or the object within the exposure thim T. That is:
T
dttyytxxgyxf0 00 ))(),(().(
Convolution method:
iterate the procedure we can get the follow equation:
)()(')(')(
)()(')(
)()()('
xxfaxfaxg
xxfxg
axgxgxf
m
l
xlaxfmaxg0
)()(')(
Convolution method:
From that we can see that the result is the convolution of the derivation of the degraded image with a comb function
Conclusion:
In this project I used such widgets: labels, texts, draws,bases,drop lists, radio buttons, slider bars, menus, module dialogue form.
I realized such functions: Region of interest, ideal low pass filter, ideal high pass filter, ideal band pass filter, butterworth filter, with different parameters, fourier transform, image histogram, histogram equalization, image blur, a inverse filter, convolution method to restore motion blur, a module dialogue form