thinnerguohall.c

#include <stdlib.h>
#include <stdio.h>
#include <stdbool.h>


struct IterRet{
    int* i;
    bool b;
};

struct IterRet thinningIteration(struct IterRet it, int x, int y, int iter)
{
    int* marker = malloc(x*y* sizeof *marker);

    for(int i= 0; i < x*y; ++i)
        marker[i] = 0;

    it.b = false;
    for (int i = 1; i < y-1; i++)
    {
        for (int j = 1; j < x-1; j++)
        {
            int p1 = it.i[(i)*x+(j)];
            int p2 = it.i[(i-1)*x+(j)];
            int p3 = it.i[(i-1)*x+(j+1)];
            int p4 = it.i[(i)*x+(j+1)];
            int p5 = it.i[(i+1)*x+(j+1)];
            int p6 = it.i[(i+1)*x+(j)];
            int p7 = it.i[(i+1)*x+(j-1)];
            int p8 = it.i[(i)*x+(j-1)];
            int p9 = it.i[(i-1)*x+(j-1)];



            int C  = ((~p2 & 0x01) & (p3 | p4)) +
                     ((~p4 & 0x01) & (p5 | p6)) +
                     ((~p6 & 0x01) & (p7 | p8)) +
                     ((~p8 & 0x01) & (p9 | p2));
            int N1 = (p9 | p2) + (p3 | p4) + (p5 | p6) + (p7 | p8);
            int N2 = (p2 | p3) + (p4 | p5) + (p6 | p7) + (p8 | p9);
            int A = iter == 0 ? (p2 | p3 | (~p5 & 0x01)) & p4 : (p6 | p7 | (~p9 & 0x01)) & p8;

            int B = (N1 < N2)? N1 : N2;
            if (p1 == 1 && C == 1 && (B == 2 || B == 3) && A == 0)
            {
                //it.b = true;
                marker[(i)*x+(j)] = 1;
            }
        }
    }

    int sum = 0;
    for(int i =0; i < x*y; i++)
        it.i[i] &= (~marker[i] & 0x01);



    free(marker);

    return it;
}


int* thinning(int* it, int x, int y)
{
        for(int i= 0; i < x*y; ++i)
            it[i] /= 255;

        struct IterRet base;
        base.i = it;
        base.b = false;

        do
        {
            base = thinningIteration(base, x, y, 0);
            base = thinningIteration(base, x, y, 1);
        }
        while (base.b);

        for(int i= 0; i < x*y; ++i)
            base.i[i] *= 255;


        return base.i;
    }

int main(int argc, char * argv[])
{
    int x, y, max;
    int i = 0, j = 0;
    FILE* fp = fopen("feep.pgm", "r");

    if(fp == NULL)
    {
        exit(EXIT_FAILURE);
    }

    fscanf(fp,"P2\n%d %d\n%d\n", &x, &y, &max);

    int* src = malloc( sizeof *src * x * y);

    for(; i < y; ++i )
    {
        for(; j < x; ++j)
        {
            fscanf(fp,"%d ", &src[i*x+j]);
            src[i*x+j] *= 255/max;
            printf("%3d ", src[i*x+j]);
        }
        fscanf(fp, "\n");
        printf("\n");
        j = 0;
    }

    fclose(fp);

    thinning(src, x, y);

    freopen("out.pgm", "w", stdout);
    printf("P2\n%d %d\n%d\n", x, y , 255);

    for(int i = 0; i < y; i++)
    {
        for(int j = 0; j < x; j++)
           printf("%d ", src[i*x+j]);
        printf("\n");
    }
    fclose(stdout);

    return 0;
}