bezier.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <math.h>

struct image {
    uint32_t size_x;
    uint32_t size_y;
    uint8_t* pixels;
};

struct point {
    double x;
    double y;
};

int print_pbm(struct image * i)
{
    uint32_t x, y;
    uint8_t* pixel = i->pixels;

    printf("P1\n");
    printf("%u %u\n", i->size_x, i->size_y);
    for (x = 0; x < i->size_x; x++) {
        for (y = 0; y < i->size_y; y++) {
            if (*(pixel++))
                printf("1 ");
            else
                printf("0 ");
        }
        printf("\n");
    }

    return 0;
}

int image_addpoint(struct image * img, struct point * pt)
{
    uint32_t x, y;
    x = (uint32_t) round(pt->x);
    y = (uint32_t) round(pt->y);
    
    if ((x > img->size_x) || (y > img->size_y))
        return -1;

    *(img->pixels + y*img->size_x + x) = 1;

    return 0;
}

struct segment {
    struct point p0;
    struct point p1;
};
//struct point bezier1(double t, struct segment * s)
struct point bezier1(struct point p0, struct point p1, double t)
{
    struct point res;
    res.x = p0.x +t*(p1.x - p0.x);
    res.y = p0.y +t*(p1.y - p0.y);
    //printf("(%lf,%lf)\n",res.x, res.y);
    
    return res;
}

struct point bezierN(uint8_t N, struct point * pts, double t)
{
    int i, n;
    struct point q;
    struct point * res = malloc(sizeof(struct point)*N);
    for (i = 0; i < N; i++)
        res[i] = pts[i];
    
    for (n = N; n > 1; n--) {
        for (i = 0; i < n-1; i++) {
            q = bezier1(res[i], res[i+1], t);
            res[i] = q;
        }
    }
    q = res[0];
    free(res);
    return q;
}

#define IMG_X (100)
#define IMG_Y (100)

int main(void)
{
    struct image img;
    struct point pt1, pt2, a,b,c, p0, p1;
    struct point pts[4];
    double t;

    img.size_x = IMG_X;
    img.size_y = IMG_Y;
    img.pixels = malloc(IMG_X*IMG_Y);
    
    memset(img.pixels, 0, img.size_x*img.size_y);

    pts[0].x = 10;
    pts[0].y = 90;
    pts[1].x = 5;
    pts[1].y = 40;
    pts[2].x = 60;
    pts[2].y = 40;
    pts[3].x = 90;
    pts[3].y = 90;

    for (t = 0.0; t < 1.0; t += 0.01) {
        pt1 = bezierN(4, pts, t);
        /*p0 = bezier1(a, b, t);
        p1 = bezier1(b, c, t);
        pt1 = bezier1(p0, p1, t);*/
        image_addpoint(&img, &pt1);
        //printf("((%u,%u))\n",pt1.x, pt1.y);
    }

    print_pbm(&img);

    free(img.pixels);
    return 0;
}