将矩形转换为圆形

Question

我正在尝试使用circle来检测物体，我使用基于yolo深度学习的darknet框架。我必须更改此函数，并且我尝试将此函数从 draw_rectangle 更改为 draw_circle，如何做到这一点？

void draw_box(image a, int x1, int y1, int x2, int y2, float r, float g, float b) {
    //normalize_image(a);
    int i;
    if (x1 < 0) x1 = 0;
    if (x1 >= a.w) x1 = a.w - 1;
    if (x2 < 0) x2 = 0;
    if (x2 >= a.w) x2 = a.w - 1;

    if (y1 < 0) y1 = 0;
    if (y1 >= a.h) y1 = a.h - 1;
    if (y2 < 0) y2 = 0;
    if (y2 >= a.h) y2 = a.h - 1;

    for (i = x1; i <= x2; ++i) {
        a.data[i + y1*a.w + 0*a.w*a.h] = r;
        a.data[i + y2*a.w + 0*a.w*a.h] = r;

        a.data[i + y1*a.w + 1*a.w*a.h] = g;
        a.data[i + y2*a.w + 1*a.w*a.h] = g;

        a.data[i + y1*a.w + 2*a.w*a.h] = b;
        a.data[i + y2*a.w + 2*a.w*a.h] = b;
    }
    for(i = y1; i <= y2; ++i) {
        a.data[x1 + i*a.w + 0*a.w*a.h] = r;
        a.data[x2 + i*a.w + 0*a.w*a.h] = r;

        a.data[x1 + i*a.w + 1*a.w*a.h] = g;
        a.data[x2 + i*a.w + 1*a.w*a.h] = g;

        a.data[x1 + i*a.w + 2*a.w*a.h] = b;
        a.data[x2 + i*a.w + 2*a.w*a.h] = b;
    }
}

void draw_box_width(image a, int x1, int y1, int x2, int y2, int w, float r, float g, float b) {
    int i;
    for (i = 0; i < w; ++i) {
        draw_box(a, x1+i, y1+i, x2-i, y2-i, r, g, b);
    }
}

所以，结果显示如下:

https://i.imgur.com/b7Bl9Iv.png

我想把它变成一个圆圈

Answer 1

这是 Bresenham 算法的简单实现，用于在图像上绘制省略号(改编自 https://gist.github.com/bert/1085538 ):

void set_pixel(image a, int x, int y, float r, float g, float b) {
    if (x >= 0 && x < a.w && y >= 0 && y < a.h) {
        a.data[x + y * a.w + 0 * a.w * a.h] = r;
        a.data[x + y * a.w + 1 * a.w * a.h] = g;
        a.data[x + y * a.w + 2 * a.w * a.h] = b;
    }
}

void plot_ellipsis_rect(image a, int x0, int y0, int x1, int y1, float r, float g, float b) {
   int a = abs(x1 - x0), b = abs(y1 - y0), b1 = b & 1; /* values of diameter */
   long dx = 4 * (1 - a) * b * b, dy = 4 * (b1 + 1) * a * a; /* error increment */
   long err = dx + dy + b1 * a * a, e2; /* error of 1.step */

   y0 += (b + 1) / 2;
   y1 = y0 - b1;   /* starting pixel */
   a = 8 * a * a;
   b1 = 8 * b * b;
   do {
       set_pixel(a, x1, y0, r, g, b); /*   I. Quadrant */
       set_pixel(a, x0, y0, r, g, b); /*  II. Quadrant */
       set_pixel(a, x0, y1, r, g, b); /* III. Quadrant */
       set_pixel(a, x1, y1, r, g, b); /*  IV. Quadrant */
       e2 = 2 * err;
       if (e2 >= dx) {
          x0++;
          x1--;
          err += dx += b1;
       }
       if (e2 <= dy) {
          y0++;
          y1--;
          err += dy += a;
       }
   } while (x0 <= x1);
   while (y0 - y1 < b) {  /* too early stop of flat ellipses a=1 */
       set_pixel(a, x0 - 1, y0, r, g, b); /* -> finish tip of ellipse */
       set_pixel(a, x1 + 1, y0++, r, g, b); 
       set_pixel(a, x0 - 1, y1, r, g, b);
       set_pixel(a, x1 + 1, y1--, r, g, b); 
   }
}