node-fontnik/src/distmap.c

#include "edtaa4func.h"
#include "distmap.h"

#include <stdlib.h>
#include <string.h>

unsigned char *
make_distance_map(unsigned char *img,
                  unsigned int src_width, unsigned int src_height, int buffer)
{
    int width = distmap_size;
    int height = distmap_size;

    short *xdist = (short *)  malloc(width * height * sizeof(short));
    short *ydist = (short *)  malloc(width * height * sizeof(short));
    double *gx      = (double *) malloc(width * height * sizeof(double));
    double *gy      = (double *) malloc(width * height * sizeof(double));
    double *data    = (double *) calloc(width * height, sizeof(double));
    double *outside = (double *) calloc(width * height, sizeof(double));
    double *inside  = (double *) calloc(width * height, sizeof(double));
    int i;

    // Convert img into double (data)
    double img_min = 255, img_max = -255;
    for (unsigned y = 0; y < src_height; y++) {
        for (unsigned x = 0; x < src_width; x++) {
            double v = img[y * src_width + x];
            data[width * (y + buffer) + buffer + x] = v;
            if (v > img_max) {
                img_max = v;
            }
            if (v < img_min) {
                img_min = v;
            }
        }
    }
    // Rescale image levels between 0 and 1
    for (unsigned y = 0; y < src_height; y++) {
        for (unsigned x = 0; x < src_width; x++) {
            data[width * (y + buffer) + buffer + x] = (img[y * src_width + x] - img_min) / img_max;
        }
    }


    // Compute outside = edtaa4(bitmap); % Transform background (0's)
    memset(gx, 0, sizeof(double)*width * height);
    memset(gy, 0, sizeof(double)*width * height);
    computegradient(data, width, height, gx, gy);
    edtaa4(data, gx, gy, height, width, xdist, ydist, outside);
    for (i = 0; i < width * height; ++i) {
        if (outside[i] < 0) {
            outside[i] = 0.0;
        }
    }

    // Compute inside = edtaa4(1-bitmap); % Transform foreground (1's)
    memset(gx, 0, sizeof(double)*width * height);
    memset(gy, 0, sizeof(double)*width * height);
    for (i = 0; i < width * height; ++i) {
        data[i] = 1 - data[i];
    }
    computegradient(data, width, height, gx, gy);
    edtaa4(data, gx, gy, height, width, xdist, ydist, inside);
    for (i = 0; i < width * height; ++i) {
        if (inside[i] < 0) {
            inside[i] = 0.0;
        }
    }

    // distmap = outside - inside; % Bipolar distance field
    unsigned char *out = (unsigned char *) malloc(width * height * sizeof(unsigned char));
    for (i = 0; i < width * height; ++i) {
        outside[i] -= inside[i];
        outside[i] = 64 + outside[i] * 32;
        if (outside[i] < 0) {
            outside[i] = 0;
        }
        if (outside[i] > 255) {
            outside[i] = 255;
        }
        out[i] = 255 - (unsigned char) outside[i];
        //out[i] = (unsigned char) outside[i];
    }

    free(xdist);
    free(ydist);
    free(gx);
    free(gy);
    free(data);
    free(outside);
    free(inside);
    return out;
}