morphological thinning for openFrameworks

thin.h

#pragma once
#include "ofMain.h"
inline void thin(ofPixels& img) {
	int w = img.getWidth(), h = img.getHeight();
	int ia1=-w-1,ia2=-w-0,ia3=-w+1,ib1=-0-1,ib3=-0+1,ic1=+w-1,ic2=+w-0,ic3=+w+1;
	unsigned char* p = img.getPixels();
	vector<unsigned int> q;
	for(int y = 1; y + 1 < h; y++) {
		for(int x = 1; x + 1 < w; x++) {
			int i = y * w + x;
			if(p[i]) {
				q.push_back(i);
			}
		}
	}
	int n = q.size();	
	for(int i=0;i<n;i++){int j=q[i];if(!p[j+ia1]&&!p[j+ia2]&&!p[j+ia3]&&p[j+ic1]&&p[j+ic2]&&p[j+ic3]){p[j]=0;}}
	for(int i=0;i<n;i++){int j=q[i];if(!p[j+ia3]&&!p[j+ib3]&&!p[j+ic3]&&p[j+ia1]&&p[j+ib1]&&p[j+ic1]){p[j]=0;}}
	for(int i=0;i<n;i++){int j=q[i];if(!p[j+ic1]&&!p[j+ic2]&&!p[j+ic3]&&p[j+ia1]&&p[j+ia2]&&p[j+ia3]){p[j]=0;}}
	for(int i=0;i<n;i++){int j=q[i];if(!p[j+ia1]&&!p[j+ib1]&&!p[j+ic1]&&p[j+ia3]&&p[j+ib3]&&p[j+ic3]){p[j]=0;}}
	for(int i=0;i<n;i++){int j=q[i];if(!p[j+ia2]&&!p[j+ia3]&&!p[j+ib3]&&p[j+ib1]&&p[j+ic2]){p[j]=0;}}
	for(int i=0;i<n;i++){int j=q[i];if(!p[j+ib3]&&!p[j+ic3]&&!p[j+ic2]&&p[j+ib1]&&p[j+ia2]){p[j]=0;}}
	for(int i=0;i<n;i++){int j=q[i];if(!p[j+ic2]&&!p[j+ic1]&&!p[j+ib1]&&p[j+ia2]&&p[j+ib3]){p[j]=0;}}
	for(int i=0;i<n;i++){int j=q[i];if(!p[j+ib1]&&!p[j+ia1]&&!p[j+ia2]&&p[j+ic2]&&p[j+ib3]){p[j]=0;}}
}