基于C语言实现线画图元生成算法【100012533】

# 线画图元生成算法 **实验目的** 掌握 DDA 算法和 Bresenham 直线算法 **实验内容** 自定义直线段起始点和终点坐标； 采用不同的彩色显示两种算法生成的直线结果； 为突出显示效果，采用网格表示像素。 **实验结果** **实验环境** OS：windows10 IDE：VS2019 使用库:openGL + glfw3 DDA 算法 鉴于 openGL 不能自动生成网格，我自己写了一段代码来生成网格。定义直接在屏幕上输出的坐标为实坐标，在网格上输出的坐标为虚拟坐标。 定义网格的粒度为 PIXLE = 10；  定义：TO_VIRTUAL_PIXEL 转到虚拟像素 TO_REAL_PIXEL 转到实际像素  结果如图  - Bresenham 算法 - Bersenham 的一般算法针对 x 正向增大且斜率 0<k<1.关键在于拓展此算法使其对于任意的线段都有效。现在仅对八分之一坐标有效 - 当 k > 1 时，注意到仅将 x 和 y 的位置对调即可，区域拓展为一个象限 - 当 x 向负向增长的时候，把原式里的 x + 1 改为 x – 1 即可。区域拓展为两个现象 - 对传入的参数进行控制，使得起点的 y 值总是小于终点的 y 值（如果不满足，就交换参数传入的顺序），区域拓展为四个象限   实验分析和总结 本次实验重点学习了直线生成算法。此算法在原理上相对简单，关键在于对算法的优化.DDA 算法把原先的乘法计算转变为浮点数加法。Bersenham 算法又在此基础上把浮点数加法改为整数加法，进一步提高了效率。 源代码 ```c++ # include<iostream> # include<math.h> # include<GLFW/glfw3.h> # include<gl/GL.h> # define ROUND(x) ((int)(x + 0.5)) # define PIXEL 10 # define TO_VIRTUAL_PIXEL(real) (real/PIXEL) # define TO_REAL_PIXEL(x) (x*PIXEL) //#define DDA # define BERSENHAM void myDDA_template(int x0, int y0, int x1, int y1); void Bersenham_template(int x0, int y0, int x1, int y1); void Bersenham_template_1(int dx, int dy, int x, int y, int degree); void draw_pixel(int x, int y) { printf("Draw_Pixel(%d , %d)\n", x, y); int real_x = TO_REAL_PIXEL(x); int real_y = TO_REAL_PIXEL(y); glColor3f(1.0, 0.0, 0.0); glPointSize(1); glBegin(GL_POINTS); for (int i = 0; i < PIXEL; i++) { for (int j = 0; j < PIXEL; j++) { glVertex2i(real_x + i, real_y + j); } } glEnd(); } void draw_grid(int width, int heigh) { glColor3f(0.0, 1.0, 0.0); glPointSize(1); glBegin(GL_POINTS); for (int x = 0; x < width; x = x + PIXEL) { for (int y = 0; y < heigh; y++) { glVertex2i(x, y); } } for (int y = 0; y < heigh; y = y + PIXEL) { for (int x = 0; x < width; x++) { glVertex2i(x, y); } } glEnd(); } void myDDA(int x0, int y0, int x1, int y1) { myDDA_template(TO_VIRTUAL_PIXEL(x0), TO_VIRTUAL_PIXEL(y0), TO_VIRTUAL_PIXEL(x1), TO_VIRTUAL_PIXEL(y1)); } void myDDA_template(int x0, int y0, int x1, int y1) { //这里都使用虚拟坐标进行计算 //printf("%d %d %d %d \n", x0, y0, x1, y1); draw_pixel(x0, y0); float x = x0, y = y0; float dx = x1 - x0; float dy = y1 - y0; int steps = (int)(abs(dx) > abs(dy)) ? abs(dx) : abs(dy); float xinc = dx / steps; float yinc = dy / steps; for (int i = 0; i < steps; i++) { += xinc; += yinc; //printf("draw pixel (%d,%d) \n", ROUND(x), ROUND(y)); draw_pixel(ROUND(x), ROUND(y)); } } void Bersenham(int x0, int y0, int x1, int y1) { if (y1 > y0) { Bersenham_template(TO_VIRTUAL_PIXEL(x0), TO_VIRTUAL_PIXEL(y0), TO_VIRTUAL_PIXEL(x1), TO_VIRTUAL_PIXEL(y1)); } else { Bersenham_template(TO_VIRTUAL_PIXEL(x1), TO_VIRTUAL_PIXEL(y1), TO_VIRTUAL_PIXEL(x0), TO_VIRTUAL_PIXEL(y0)); } } void Bersenham_template(int x0, int y0, int x1, int y1) { printf("Bersenham args (%d , %d , %d , %d)\n", x0, y0, x1, y1); draw_pixel(x0, y0); int x = x0; int y = y0; int dx = abs(x1 - x0); int dy = abs(y1 - y0); int p0; if(dy > dx) { Bersenham_template_1(dy, dx, x0, y0, (x1 > x0)); } else { Bersenham_template_1(dx, dy, x0, y0, (x1 > x0)); } } // for 0<k <1 // degree 分为正向和反向 void Bersenham_template_1(int dx, int dy, int x, int y, int degree) { int p0; = 2 * dy - dx; if (degree) { for (int i = 0; i < dx; i++) { if (p0 < 0) { draw_pixel(x + 1 + i, y); = p0 + 2 * dy; } else { y++; draw_pixel(x + 1 + i, y); = p0 + 2 * dy - 2 * dx; } } } else { for (int i = 0; i < dx; i++) { if (p0 < 0) { draw_pixel(x - 1 - i, y); = p0 + 2 * dy; } else { y++; draw_pixel(x - 1 - i, y); = p0 + 2 * dy - 2 * dx; } } } } void Init(int width, int height) { glViewport(0, 0, width, height); glMatrixMode(GL_PROJECTION); glLoadIdentity(); glOrtho(0.0, width, 0.0, height, 0.0, 1.0); } int main() { int width, height; width = 1440; height = 960; GLFWwindow* window; if (!glfwInit()) { return -1; } window = glfwCreateWindow(width, height, "Computer Graphics", NULL, NULL); if (!window) { glfwTerminate(); return -1; } glfwMakeContextCurrent(window); glfwSwapInterval(1); Init(width, height); int printed = 1; while (!glfwWindowShouldClose(window)) { //glClear(GL_COLOR_BUFFER_BIT); if (printed) { //Draw here # ifdef DDA myDDA(100, 100, 600, 300); myDDA((float)100, (float)100, (float)200, (float)0); myDDA((float)100, (float)100, (float)105, (float)200); myDDA((float)100, (float)100, (float)70, (float)200); myDDA((float)100, (float)100, (float)0, (float)100); myDDA((float)100, (float)100, (float)200, (float)100); # endif # ifdef BERSENHAM //Bersenham(0, 0, 500, 100); Bersenham(0, 0, 100, 500); Bersenham(0, 0, 0, 1000); Bersenham(1000, 500, 0, 0); Bersenham(1000, 200, 200, 800); # endif } draw_grid(width, height); glfwSwapBuffers(window); glfwPollEvents(); } glfwDestroyWindow(window); glfwTerminate(); return 0; } ```