距离变换代码实现(c代码)

#include <stdio.h>#include <stdlib.h>// Removal Function - FVs that are the Voronoi sites of Voronoi cells that do not intersect Rd are removedstatic int RemoveEDT(const float du, const float dv, const float dw, const float u, const float v, const float w){    float a = v - u;    float b = w - v;    float c = w - u;    // See Eq. 2 from Maurer et al., 2003    return ((c * dv - b * du - a * dw) > (a * b * c));}static int constructPartialVoronoi(float* D, float* g, int* h, int length){    //    // Construct partial voronoi diagram (see Maurer et al., 2003, Fig. 5, lines 1-14)    // Note: short variable names are used to mimic the notation of the paper    //    int el = -1;    for (int k = 0; k < length; k++)    {        float fk = D[k];        if (fk != -1.0f)        {            if (el < 1)            {                el++;                g[el] = fk;                h[el] = k;            }            else            {                while ((el >= 1) && RemoveEDT(g[el - 1], g[el], fk, h[el - 1], h[el], k))                {                    el--;                }                el++;                g[el] = fk;                h[el] = k;            }        }    }    return(el);}static void queryPartialVoronoi(const float* g, const int* h, const int ns, float* D, int length){    //    // Query partial Voronoi diagram (see Maurer et al., 2003, Fig. 5, lines 18-24)    //    int el = 0;    for (int k = 0; k < length; k++)    {        while ((el < ns) && ((g[el] + ((h[el] - k)*(h[el] - k))) >(g[el + 1] + ((h[el + 1] - k)*(h[el + 1] - k)))))        {            el++;        }        D[k] = g[el] + (h[el] - k)*(h[el] - k);    }}static void voronoiEDT(float* D, float* g, int* h, int length){    // Note: g and h are working vectors allocated in calling function    int ns = constructPartialVoronoi(D, g, h, length);    if (ns == -1)        return;    queryPartialVoronoi(g, h, ns, D, length);    return;}static void processDimN(int width, int height/*const mwSize *dims, const mwSize ndims*/, float *D){    // Create temporary vectors for processing along dimension N    float* g =  (float*)calloc(width, sizeof(float));    int* h = (int*)calloc(width, sizeof(int));    // 若为二维数组，则得到第一维元素总数，即行数。注意，matlab按列存储，C按行存储。    for (int k = 0; k < height; k++)    {        // Process vector        voronoiEDT(&D[k*width], g, h, width);    }    free(g);    free(h);}// mxI为输入，unsigned char*类型，mxD为输出，float* 类型// 注意，matlab中mxI是逻辑类型，需要1-mxI才是真正的输入；此处省略了这一步。// 输入为二值化图像，大于阈值的不为0，小于阈值的为0。void computeEDT(float *mxD, const unsigned char *mxI, int width, int height){    float* D1 = (float*)calloc(width, sizeof(float));    float* g  = (float*)calloc(width, sizeof(float));    int* h  = (int*)calloc(width, sizeof(int));    for (int k = 0; k < width; k++)    {        for (int i = 0; i < height; i++)        {            D1[i] = (mxI[i*width + k] == 0) ? 0.0f : -1.0f;        }        voronoiEDT(D1, g, h, height);        for (int i = 0; i < height; i++)        {            mxD[i*width + k] = D1[i];        }    }    free(D1);    free(g);    free(h);    processDimN(width, height, mxD);}