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import java.lang.Math.*;
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import java.awt.*;
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/**
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* Class containing method to apply a frequency filter to an image.
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*
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* @author Simon Horne.
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*/
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public class FreqFilter
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{
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/**
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* Method to apply a high or low pass filter to an image.
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*
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* @param input TwoDArray representing the image.
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* @param h boolean true - highpass, false - lowpass.
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* @return TwoDArray representing new image.
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*/
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public static TwoDArray filter(TwoDArray input, boolean lowpass, double r)
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{
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TwoDArray output = new TwoDArray(input.values, input.size, input.size);
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int i2, j2;
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double r2 = r * r;
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if (lowpass)
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{//if low pass filter
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for (int j = 0; j < input.size; ++j)
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{
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for (int i = 0; i < input.size; ++i)
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{
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if (i >= input.size / 2)
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{
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i2 = i - input.size;
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} else
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{
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i2 = i;
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}
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if (j >= input.size / 2)
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{
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j2 = j - input.size;
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} else
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{
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j2 = j;
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}
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double d2 = i2 * i2 + j2 * j2;
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if (d2 > r2)
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{
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output.values[i][j] = new ComplexNumber(0, 0);
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} else
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{
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output.values[i][j] = input.values[i][j];
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}
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}
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}
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} else
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{//else high pass filter
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for (int j = 0; j < input.size; ++j)
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{
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for (int i = 0; i < input.size; ++i)
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{
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if (i >= input.size / 2)
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{
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i2 = i - input.size;
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} else
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{
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i2 = i;
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}
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if (j >= input.size / 2)
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{
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j2 = j - input.size;
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} else
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{
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j2 = j;
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}
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double d2 = i2 * i2 + j2 * j2;
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if (d2 > r2)
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{
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output.values[i][j] = input.values[i][j];
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} else
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{
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output.values[i][j] = new ComplexNumber(0, 0);
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}
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}
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}
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}
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return output;
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}
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/**
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* Method to apply a high or low pass filter to an image.
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*/
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public static void filterCorners(double[] io, int size, boolean lowpass, double radius)
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{
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int i2, j2;
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double r2 = radius * radius;
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if (lowpass)
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{//if low pass filter
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for (int j = 0; j < size; ++j)
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{
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for (int i = 0; i < size; ++i)
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{
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i2 = i;
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if (i2 >= size / 2)
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{
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i2 -= size;
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}
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j2 = j;
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if (j2 >= size / 2)
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{
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j2 -= size;
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}
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double d2 = i2 * i2 + j2 * j2;
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if (d2 > r2)
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{
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io[j*size + i] = 0;
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}
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}
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}
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} else
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{//else high pass filter
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for (int j = 0; j < size; ++j)
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{
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for (int i = 0; i < size; ++i)
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{
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i2 = i;
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if (i2 >= size / 2)
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{
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i2 -= size;
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}
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j2 = j;
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if (j2 >= size / 2)
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{
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j2 -= size;
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}
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double d2 = i2 * i2 + j2 * j2;
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if (d2 <= r2)
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{
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io[j*size + i] = 0;
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}
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}
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}
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}
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}
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/**
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* Method to apply a high or low pass filter to an image.
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*/
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public static void filterCenter(double[] io, int size, boolean lowpass, double radius)
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{
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int i2, j2;
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double r2 = radius * radius;
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if (lowpass)
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{//if low pass filter
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for (int j = 0; j < size; ++j)
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{
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for (int i = 0; i < size; ++i)
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{
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i2 = i - size/2;
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j2 = j - size/2;
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double d2 = i2 * i2 + j2 * j2;
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if (d2 > r2)
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{
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io[j*size + i] = 0;
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}
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}
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}
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} else
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{//else high pass filter
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for (int j = 0; j < size; ++j)
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{
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for (int i = 0; i < size; ++i)
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{
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i2 = i - size/2;
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j2 = j - size/2;
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double d2 = i2 * i2 + j2 * j2;
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if (d2 <= r2)
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{
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io[j*size + i] = 0;
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}
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}
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}
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}
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}
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}
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