Introduction

 

Magnifying glass in the image

 

View more images

 

Geometrical transforms

 

Brightness profile

 

Histogram

 »

Fourier transform

 

Features

 

Brightness/contrast corrrections

 

Flat-Field corrections

 

Inhomogeneous lighting correction

 

Gama correction

 

Noise generation

 

Arithmetical and logical operation

 

Look Up Tables

 

2D convolution

 

Objects drawing

 

Morphological operations

 

Nonlinear filters

 

Bit fields

 

Sobel edge detection

 

Averaging

 

Colour images

 

 MIPS 2.0 - Medical/Microscopy Image Processing Software

 

 

 

Spectrum view

 »

Filtering

 

 

FILTERING


Discrete Fourier Transform / Filtering

Frequency domain spectrum filtering can be performed by 2D DFT. By the transform of image f(x,y)  we obtain F(u,v). If the H(u,v) represents filtr, filtering can then be written as:

                                  

After the forward FFT we select suitable filter and set their properties - cutoff frequency, intensity, possibly other constants. Within the SW MIPS there are available the following filters:

        

We can choose whether we want to plot the real or imaginary component, the amplitude or the phase component after performing a direct FFT. At each step, the result after the operation can be displayed in a magnified window. After the backward FFT, the resulting image can be cropped to match the size of the original image.

Preview

 

 

                                           Working window for FFT filtering

 

 

  

                        

  Methods of image completion             Visualization methods

 

 

 

                

       List of available filters                    Methods of inverse DFT

 

 

 

 

                           Next functions

Examples

1. Low-pass filter

 

   

 

              Image before filtering                                    Image spectrum

 

 

 

   

 

     Image spectrum after filtering                           Image after filtering

 

2. High-pass filter

 

   

 

              Image before filtering                                    Image spectrum

 

 

 

   

 

     Image spectrum after fltering                           Image after filtering

 

3. Band-pass filter

 

   

 

              Image before filtering                                     Image spectrum

 

 

 

   

 

     Image spectrum after filtering                           Image after filtering

 

 


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