Median filter source code

// medianfilter.cpp - impelementation of 
// 1D and 2D median filter routines
//
// The code is property of LIBROW
// You can use it on your own
// When utilizing credit LIBROW site
#include <memory.h>
#include "medianfilter.h"
// 1D MEDIAN FILTER implementation
// signal - input signal
// result - output signal
// N - length of the signal
void _medianfilter(const element* signal, element* result, int N)
{
 // Move window through all elements of the signal
 for (int i = 2; i < N - 2; ++i) { // Pick up window elements
 element window[5];
 for (int j = 0; j < 5; ++j) window[j] = signal[i - 2 + j]; // Order elements (only half of them)
 for (int j = 0; j < 3; ++j) { // Find position of minimum element
 int min = j;
 for (int k = j + 1; k < 5; ++k) if (window[k] < window[min]) min = k; // Put found minimum element in its place
 const element temp = window[j];
 window[j] = window[min];
 window[min] = temp;
 }
 // Get result - the middle element
 result[i - 2] = window[2];
 }
}
// 1D MEDIAN FILTER wrapper
// signal - input signal
// result - output signal
// N - length of the signal
void medianfilter(element* signal, element* result, int N)
{
 // Check arguments
 if (!signal || N < 1) return;
 // Treat special case N = 1
 if (N == 1)
 {
 if (result)
 result[0] = signal[0];
 return;
 }
 // Allocate memory for signal extension
 element* extension = new element[N + 4];
 // Check memory allocation
 if (!extension)
 return;
 // Create signal extension
 memcpy(extension + 2, signal, N * sizeof(element));
 for (int i = 0; i < 2; ++i) { extension[i] = signal[1 - i]; extension[N + 2 + i] = signal[N - 1 - i]; } // Call median filter implementation
 _medianfilter(extension, result ? result : signal, N + 4);
 // Free memory
 delete[] extension;
}
// 2D MEDIAN FILTER implementation
// image - input image
// result - output image
// N - width of the image
// M - height of the image
void _medianfilter(const element* image, element* result, int N, int M)
{
 // Move window through all elements of the image
 for (int m = 1; m < M - 1; ++m) for (int n = 1; n < N - 1; ++n) { // Pick up window elements
 int k = 0;
 element window[9];
 for (int j = m - 1; j < m + 2; ++j) for (int i = n - 1; i < n + 2; ++i) window[k++] = image[j * N + i]; // Order elements (only half of them)
 for (int j = 0; j < 5; ++j) { // Find position of minimum element
 int min = j;
 for (int l = j + 1; l < 9; ++l) if (window[l] < window[min]) min = l; // Put found minimum element in its place
 const element temp = window[j];
 window[j] = window[min];
 window[min] = temp;
 }
 // Get result - the middle element
 result[(m - 1) * (N - 2) + n - 1] = window[4];
 }
}
// 2D MEDIAN FILTER wrapper
// image - input image
// result - output image
// N - width of the image
// M - height of the image
void medianfilter(element* image, element* result, int N, int M)
{
 // Check arguments
 if (!image || N < 1 || M < 1) return;
 // Allocate memory for signal extension
 element* extension = new element[(N + 2) * (M + 2)];
 // Check memory allocation
 if (!extension)
 return;
 // Create image extension
 for (int i = 0; i < M; ++i) { memcpy(extension + (N + 2) * (i + 1) + 1, image + N * i, N * sizeof(element));
 extension[(N + 2) * (i + 1)] = image[N * i];
 extension[(N + 2) * (i + 2) - 1] = image[N * (i + 1) - 1];
 }
 // Fill first line of image extension
 memcpy(extension,
 extension + N + 2,
 (N + 2) * sizeof(element));
 // Fill last line of image extension
 memcpy(extension + (N + 2) * (M + 1),
 extension + (N + 2) * M,
 (N + 2) * sizeof(element));
 // Call median filter implementation
 _medianfilter(extension, result ? result : image, N + 2, M + 2);
 // Free memory
 delete[] extension;
}