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| /**
*
*/
package millie.operator;
import millie.image.Image;
import millie.operator.commons.ImageOperator;
/**
*
* @author Xavier Philippeau
*
*/
public class SkeletonOperator implements ImageOperator {
// Gray Level Threshold
private int threshold = 0;
// Smoothing pattern
private byte[] pattern1={-1,1,0,1,0,0,0,0};
private byte[] pattern2={0,1,0,1,-1,0,0,0};
private byte[] pattern3={0,0,-1,1,0,1,0,0};
private byte[] pattern4={0,0,0,1,0,1,-1,0};
private byte[] pattern5={0,0,0,0,-1,1,0,1};
private byte[] pattern6={-1,0,0,0,0,1,0,1};
private byte[] pattern7={0,1,0,0,0,0,-1,1};
private byte[] pattern8={0,1,-1,0,0,0,0,1};
public SkeletonOperator(int threshold) {
this.threshold=threshold;
}
// Neighbourhood
private int neighbourhood(byte[][] c,int x,int y) {
int neighbourhood=0;
if (c[x-1][y-1]==1) neighbourhood++;
if (c[x-1][y ]==1) neighbourhood++;
if (c[x-1][y+1]==1) neighbourhood++;
if (c[x ][y+1]==1) neighbourhood++;
if (c[x+1][y+1]==1) neighbourhood++;
if (c[x+1][y ]==1) neighbourhood++;
if (c[x+1][y-1]==1) neighbourhood++;
if (c[x ][y-1]==1) neighbourhood++;
return neighbourhood;
}
// Transitions Count
private int transitions(byte[][] c,int x,int y) {
int transitions=0;
if (c[x-1][y-1]==0 && c[x-1][y ]==1) transitions++;
if (c[x-1][y ]==0 && c[x-1][y+1]==1) transitions++;
if (c[x-1][y+1]==0 && c[x ][y+1]==1) transitions++;
if (c[x ][y+1]==0 && c[x+1][y+1]==1) transitions++;
if (c[x+1][y+1]==0 && c[x+1][y ]==1) transitions++;
if (c[x+1][y ]==0 && c[x+1][y-1]==1) transitions++;
if (c[x+1][y-1]==0 && c[x ][y-1]==1) transitions++;
if (c[x ][y-1]==0 && c[x-1][y-1]==1) transitions++;
return transitions;
}
// Match a pattern
private boolean matchPattern(byte[][] c,int x,int y,byte[] pattern) {
if (pattern[0]!=-1 && pattern[0]!=c[x-1][y-1]) return false;
if (pattern[1]!=-1 && pattern[1]!=c[x-1][y ]) return false;
if (pattern[2]!=-1 && pattern[2]!=c[x-1][y+1]) return false;
if (pattern[3]!=-1 && pattern[3]!=c[x ][y+1]) return false;
if (pattern[4]!=-1 && pattern[4]!=c[x+1][y+1]) return false;
if (pattern[5]!=-1 && pattern[5]!=c[x+1][y ]) return false;
if (pattern[6]!=-1 && pattern[6]!=c[x+1][y-1]) return false;
if (pattern[7]!=-1 && pattern[7]!=c[x ][y-1]) return false;
return true;
}
// Match one of the 8 patterns
private boolean matchOneOfPatterns(byte[][] c,int x,int y) {
if (matchPattern(c,x,y,pattern1)) return true;
if (matchPattern(c,x,y,pattern2)) return true;
if (matchPattern(c,x,y,pattern3)) return true;
if (matchPattern(c,x,y,pattern4)) return true;
if (matchPattern(c,x,y,pattern5)) return true;
if (matchPattern(c,x,y,pattern6)) return true;
if (matchPattern(c,x,y,pattern7)) return true;
if (matchPattern(c,x,y,pattern8)) return true;
return false;
}
/**
* Skeletonize the image using succesive thinning.
*
* @param image the image in an array[x][y] of values "0" or "1"
* @param width of the image = 1st dimension of the array
* @param height of the image = 2nd dimension of the array
*/
public void thinning(byte[][] image,int width,int height) {
// 3 columns back-buffer (original values)
byte[][] buffer = new byte[3][height];
// initialize the back-buffer
for(int y=0;y<height;y++) {
buffer[0][y]=0;
buffer[1][y]=image[0][y];
buffer[2][y]=image[1][y];
}
// loop until idempotence
for(int loop=0;;loop++) {
boolean changed=false;
// for each columns
for(int x=1;x<(width-1);x++) {
// shift the back-buffer + set the last column
byte[] swp0 = buffer[0]; buffer[0]=buffer[1]; buffer[1]=buffer[2]; buffer[2]=swp0;
for(int y=0;y<height;y++) buffer[2][y]=image[x+1][y];
// for each pixel
for(int y=1;y<(height-1);y++) {
// pixel value
int v = image[x][y];
// pixel not set -> next
if (v==0) continue;
// is a boundary/extremity ?
int currentNeighbourhood = neighbourhood(buffer,1,y);
if (currentNeighbourhood<=1) continue;
if (currentNeighbourhood>=6) continue;
// is a connection ?
int transitionsCount = transitions(image,x,y);
if (transitionsCount==1 && currentNeighbourhood<=3) continue;
// no -> remove this pixel
if (transitionsCount==1) {
changed=true;
image[x][y]=0;
continue;
}
// can we delete this pixel ?
boolean matchOne = matchOneOfPatterns(image,x,y);
// yes -> remove this pixel
if (matchOne) {
changed=true;
image[x][y]=0;
continue;
}
}
}
// no change -> return result
if (!changed) return;
}
}
@Override
public void compute(Image out, Image in) throws Exception {
int width = in.getWidth();
int height = in.getHeight();
out.resize(width, height);
// create binary array from input image
byte[][] array = new byte[width][height];
for(int y=1;y<height-1;y++) {
for(int x=1;x<width-1;x++) {
int value = 0;
for(int i=0;i<in.getNumComponents();i++)
value+=(int)in.getPixel(x, y, i);
value/=in.getNumComponents();
if (value>=threshold) array[x][y]=1;
}
}
// perform the thinning
thinning(array, width, height);
// create output image
for(int y=1;y<height-1;y++) {
for(int x=1;x<width-1;x++) {
for(int i=0;i<in.getNumComponents();i++)
if (array[x][y]==0)
out.setPixel(x, y, i, 0);
else
out.setPixel(x, y, i, in.getPixel(x, y, i));
}
}
}
} |
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