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/**
* @author Pacien TRAN-GIRARD
* @author Timothée FLOURE
*/
public final class Filter {
/**
* Get a pixel without accessing out of bounds
*
* @param gray a HxW float array
* @param row Y coordinate
* @param col X coordinate
* @return nearest valid pixel color
*/
public static float at(float[][] gray, int row, int col) {
int maxRow = gray.length - 1;
int maxCol = gray[0].length - 1;
if (row < 0) row = 0;
if (col < 0) col = 0;
if (row > maxRow) row = maxRow;
if (col > maxCol) col = maxCol;
return gray[row][col];
}
/**
* Convolve a single-channel image with specified kernel.
*
* @param gray a HxW float array
* @param kernel a MxN float array, with M and N odd
* @return a HxW float array
*/
public static float[][] filter(float[][] gray, float[][] kernel) {
int width = gray[0].length;
int height = gray.length;
float[][] filteredImage = new float[height][width];
for (int row = 0; row < height; ++row) {
for (int col = 0; col < width; ++col) {
float pixelCore[][] = {
{Filter.at(gray, row-1, col-1),Filter.at(gray, row-1, col),Filter.at(gray, row-1, col+1)},
{Filter.at(gray, row, col-1),Filter.at(gray, row, col),Filter.at(gray, row, col+1)},
{Filter.at(gray, row+1, col-1),Filter.at(gray, row+1, col),Filter.at(gray, row+1, col+1)}
};
for (int i = 0; i < kernel[0].length; i++) {
for (int j = 0; j < kernel.length; j++) {
filteredImage[row][col] += kernel[i][j] * pixelCore[i][j];
}
}
}
}
return filteredImage;
}
/**
* Smooth a single-channel image
*
* @param gray a HxW float array
* @return a HxW float array
*/
public static float[][] smooth(float[][] gray) {
float smoothCore[][]={
{0.1f,0.1f,0.1f},
{0.1f,0.2f,0.1f},
{0.1f,0.1f,0.1f}
};
float[][] smoothtImage = Filter.filter(gray, smoothCore);
return smoothtImage;
}
/**
* Compute horizontal Sobel filter
*
* @param gray a HxW float array
* @return a HxW float array
*/
public static float[][] sobelX(float[][] gray) {
float sobelXCore[][]= {
{-1,0,1},
{-2,0,2},
{-1,0,1}
};
float[][] sobelXImage = Filter.filter(gray, sobelXCore);
return sobelXImage;
}
/**
* Compute vertical Sobel filter
*
* @param gray a HxW float array
* @return a HxW float array
*/
public static float[][] sobelY(float[][] gray) {
float sobelYCore[][]={
{-1,-2,-1},
{0,0,0},
{1,2,1}
};
float[][] sobelYImage = Filter.filter(gray, sobelYCore);
System.out.println(sobelYImage[0][0]);
return sobelYImage;
}
/**
* Compute the magnitude of combined Sobel filters
*
* @param gray a HxW float array
* @return a HxW float array
*/
public static float[][] sobel(float[][] gray) {
float[][] x = Filter.sobelX(gray);
float[][] y = Filter.sobelY(gray);
int width = gray[0].length;
int height = gray.length;
float[][] sobelImage = new float[height][width];
for (int row = 0; row < height; ++row) {
for (int col = 0; col < width; ++col) {
sobelImage[row][col] = (float) Math.sqrt(Math.pow(x[row][col],2)+Math.pow(y[row][col],2));
}
}
return sobelImage;
}
}
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