package com.gloomyfish.filter.study;
import java.awt.image.BufferedImage;
import java.util.Arrays;
public class CannyEdgeFilter extends AbstractBufferedImageOp {
private float gaussianKernelRadius = 2f;
private int gaussianKernelWidth = 16;
private float lowThreshold;
private float highThreshold;
private int width;
private int height;
private float[] data;
private float[] magnitudes;
public CannyEdgeFilter() {
lowThreshold = 2.5f;
highThreshold = 7.5f;
gaussianKernelRadius = 2f;
gaussianKernelWidth = 16;
}
public float getGaussianKernelRadius() {
return gaussianKernelRadius;
}
public void setGaussianKernelRadius(float gaussianKernelRadius) {
this.gaussianKernelRadius = gaussianKernelRadius;
}
public int getGaussianKernelWidth() {
return gaussianKernelWidth;
}
public void setGaussianKernelWidth(int gaussianKernelWidth) {
this.gaussianKernelWidth = gaussianKernelWidth;
}
public float getLowThreshold() {
return lowThreshold;
}
public void setLowThreshold(float lowThreshold) {
this.lowThreshold = lowThreshold;
}
public float getHighThreshold() {
return highThreshold;
}
public void setHighThreshold(float highThreshold) {
this.highThreshold = highThreshold;
}
@Override
public BufferedImage filter(BufferedImage src, BufferedImage dest) {
width = src.getWidth();
height = src.getHeight();
if (dest == null)
dest = createCompatibleDestImage(src, null);
int[] inPixels = new int[width * height];
int[] outPixels = new int[width * height];
getRGB(src, 0, 0, width, height, inPixels);
int index = 0;
for (int row = 0; row < height; row++) {
int ta = 0, tr = 0, tg = 0, tb = 0;
for (int col = 0; col < width; col++) {
index = row * width + col;
ta = (inPixels[index] >> 24) & 0xff;
tr = (inPixels[index] >> 16) & 0xff;
tg = (inPixels[index] >> 8) & 0xff;
tb = inPixels[index] & 0xff;
int gray = (int) (0.299 * tr + 0.587 * tg + 0.114 * tb);
inPixels[index] = (ta << 24) | (gray << 16) | (gray << 8)
| gray;
}
}
float kernel[][] = new float[gaussianKernelWidth][gaussianKernelWidth];
for(int x=0; x<gaussianKernelWidth; x++)
{
for(int y=0; y<gaussianKernelWidth; y++)
{
kernel[x][y] = gaussian(x, y, gaussianKernelRadius);
}
}
int krr = (int)gaussianKernelRadius;
for (int row = 0; row < height; row++) {
for (int col = 0; col < width; col++) {
index = row * width + col;
double weightSum = 0.0;
double redSum = 0;
for(int subRow=-krr; subRow<=krr; subRow++)
{
int nrow = row + subRow;
if(nrow >= height || nrow < 0)
{
nrow = 0;
}
for(int subCol=-krr; subCol<=krr; subCol++)
{
int ncol = col + subCol;
if(ncol >= width || ncol <=0)
{
ncol = 0;
}
int index2 = nrow * width + ncol;
int tr1 = (inPixels[index2] >> 16) & 0xff;
redSum += tr1*kernel[subRow+krr][subCol+krr];
weightSum += kernel[subRow+krr][subCol+krr];
}
}
int gray = (int)(redSum / weightSum);
outPixels[index] = gray;
}
}
data = new float[width * height];
magnitudes = new float[width * height];
for (int row = 0; row < height; row++) {
for (int col = 0; col < width; col++) {
index = row * width + col;
float xg = (getPixel(outPixels, width, height, col, row+1) -
getPixel(outPixels, width, height, col, row) +
getPixel(outPixels, width, height, col+1, row+1) -
getPixel(outPixels, width, height, col+1, row))/2.0f;
float yg = (getPixel(outPixels, width, height, col, row)-
getPixel(outPixels, width, height, col+1, row) +
getPixel(outPixels, width, height, col, row+1) -
getPixel(outPixels, width, height, col+1, row+1))/2.0f;
data[index] = hypot(xg, yg);
if(xg == 0)
{
if(yg > 0)
{
magnitudes[index]=90;
}
if(yg < 0)
{
magnitudes[index]=-90;
}
}
else if(yg == 0)
{
magnitudes[index]=0;
}
else
{
magnitudes[index] = (float)((Math.atan(yg/xg) * 180)/Math.PI);
}
magnitudes[index] += 90;
}
}
Arrays.fill(magnitudes, 0);
for (int row = 0; row < height; row++) {
for (int col = 0; col < width; col++) {
index = row * width + col;
float angle = magnitudes[index];
float m0 = data[index];
magnitudes[index] = m0;
if(angle >=0 && angle < 22.5)
{
float m1 = getPixel(data, width, height, col-1, row);
float m2 = getPixel(data, width, height, col+1, row);
if(m0 < m1 || m0 < m2)
{
magnitudes[index] = 0;
}
}
else if(angle >= 22.5 && angle < 67.5)
{
float m1 = getPixel(data, width, height, col+1, row-1);
float m2 = getPixel(data, width, height, col-1, row+1);
if(m0 < m1 || m0 < m2)
{
magnitudes[index] = 0;
}
}
else if(angle >= 67.5 && angle < 112.5)
{
float m1 = getPixel(data, width, height, col, row+1);
float m2 = getPixel(data, width, height, col, row-1);
if(m0 < m1 || m0 < m2)
{
magnitudes[index] = 0;
}
}
else if(angle >=112.5 && angle < 157.5)
{
float m1 = getPixel(data, width, height, col-1, row-1);
float m2 = getPixel(data, width, height, col+1, row+1);
if(m0 < m1 || m0 < m2)
{
magnitudes[index] = 0;
}
}
else if(angle >=157.5)
{
float m1 = getPixel(data, width, height, col, row+1);
float m2 = getPixel(data, width, height, col, row-1);
if(m0 < m1 || m0 < m2)
{
magnitudes[index] = 0;
}
}
}
}
float min = 255;
float max = 0;
for(int i=0; i<magnitudes.length; i++)
{
if(magnitudes[i] == 0) continue;
min = Math.min(min, magnitudes[i]);
max = Math.max(max, magnitudes[i]);
}
System.out.println("Image Max Gradient = " + max + " Mix Gradient = " + min);
Arrays.fill(data, 0);
int offset = 0;
for (int row = 0; row < height; row++) {
for (int col = 0; col < width; col++) {
if(magnitudes[offset] >= highThreshold && data[offset] == 0)
{
edgeLink(col, row, offset, lowThreshold);
}
offset++;
}
}
for(int i=0; i<inPixels.length; i++)
{
int gray = clamp((int)data[i]);
outPixels[i] = gray > 0 ? -1 : 0xff000000;
}
setRGB(dest, 0, 0, width, height, outPixels );
return dest;
}
public int clamp(int value) {
return value > 255 ? 255 :
(value < 0 ? 0 : value);
}
private void edgeLink(int x1, int y1, int index, float threshold) {
int x0 = (x1 == 0) ? x1 : x1 - 1;
int x2 = (x1 == width - 1) ? x1 : x1 + 1;
int y0 = y1 == 0 ? y1 : y1 - 1;
int y2 = y1 == height -1 ? y1 : y1 + 1;
data[index] = magnitudes[index];
for (int x = x0; x <= x2; x++) {
for (int y = y0; y <= y2; y++) {
int i2 = x + y * width;
if ((y != y1 || x != x1)
&& data[i2] == 0
&& magnitudes[i2] >= threshold) {
edgeLink(x, y, i2, threshold);
return;
}
}
}
}
private float getPixel(float[] input, int width, int height, int col,
int row) {
if(col < 0 || col >= width)
col = 0;
if(row < 0 || row >= height)
row = 0;
int index = row * width + col;
return input[index];
}
private float hypot(float x, float y) {
return (float) Math.hypot(x, y);
}
private int getPixel(int[] inPixels, int width, int height, int col,
int row) {
if(col < 0 || col >= width)
col = 0;
if(row < 0 || row >= height)
row = 0;
int index = row * width + col;
return inPixels[index];
}
private float gaussian(float x, float y, float sigma) {
float xDistance = x*x;
float yDistance = y*y;
float sigma22 = 2*sigma*sigma;
float sigma22PI = (float)Math.PI * sigma22;
return (float)Math.exp(-(xDistance + yDistance)/sigma22)/sigma22PI;
}
}