实验二：直线与画圆算法
实验目的： 理解光栅化，掌握几何数据如何经过一系列变换后转化为像素从而呈现在显示 设备上。
基本要求：
实现 DDA 和 Bresenham 画线算法
实现画圆算法
请勿直接调用 OpenGL 库中提供的绘制线段和圆的函数，需手动模拟如何通过绘 制像素来显示几何图形，效果可参考下图。（界面显示的是“虚拟的像素”）
可通过交互操作来确定线段的起点和终点。
实现：
1 #include<GL/glut.h>
2 #define EXIT_SUCCESS 0
3 #include<stdio.h>
4 #include<math.h>
5 // later Edition
6 int MODE = 0; // 模式代码：0-DAA算法，1-Bresenham算法，2-中点圆算法
7 bool mouseLeftDown; // 实时记录鼠标左键状态
8 bool mouseRightDown; // 实时记录鼠标左键状态
9 float mouseX, mouseY; // 实时记录鼠标位置，与下一次鼠标位置之间形成微分
10
11 int startX=0, startY=0, endX=0, endY=0;
12 int start[2] = { 0 };
13 int end[2] = { 0 };
14 float red=1.0,green=1.0, blue=0.0;
15 float PI = 3.415926535;
16
17 int arr[500][500];
18
19 void init(void)
20 {
21 //glClearColor(0.0, 0.0, 0.0, 0.0);/* select clearing color */ // 设置背景颜色为黑色
22 //glMatrixMode(GL_MODELVIEW);
23 glClearColor(0.0, 0.0, 0.0, 0.0); /* white background */
24 glColor3f(1.0, 0.0, 0.0); /* draw in red */
25
26 /* set up viewing: */
27 /* 500 x 500 window with origin lower left */
28
29 glMatrixMode(GL_PROJECTION);
30 glLoadIdentity();
31 gluOrtho2D(0.0, 500.0, 0.0, 500.0);
32 glMatrixMode(GL_MODELVIEW);
33 }
34
35
36
37
38 #define RED 1233
39 #define BLUE 1234
40 #define GREEN 1235
41 #define WHITE 12366
42 #define YELLOW 12367
43 #define DAA_LINE 12368
44 #define BRES_LINE 12369
45 #define CIRCLE 12370
46 void processMenuEvents(int option) {
47 //option，就是传递过来的value的值。
48 switch (option) {
49 case RED:
50 red = 1.0;
51 green = 0.0;
52 blue = 0.0; break;
53 case GREEN:
54 red = 0.0;
55 green = 1.0;
56 blue = 0.0; break;
57 case BLUE:
58 red = 0.0;
59 green = 0.0;
60 blue = 1.0; break;
61 case WHITE:
62 red = 1.0;
63 green = 1.0;
64 blue = 1.0; break;
65 case YELLOW:
66 red = 1.0;
67 green = 1.0;
68 blue = 0.0;break;
69 case DAA_LINE:
70 MODE = 0;break;
71 case BRES_LINE:
72 MODE = 1;break;
73 case CIRCLE:
74 MODE = 2;break;
75 }
76 }
77 void createGLUTMenus() {
78
79 int menu;
80
81 // 创建菜单并告诉GLUT，processMenuEvents处理菜单事件。
82 menu = glutCreateMenu(processMenuEvents);
83
84 //给菜单增加条目
85 glutAddMenuEntry("红色", RED);
86 glutAddMenuEntry("蓝色", BLUE);
87 glutAddMenuEntry("绿色", GREEN);
88 glutAddMenuEntry("白色", WHITE);
89 glutAddMenuEntry("黄色", YELLOW);
90 glutAddMenuEntry("DAA_LINE", DAA_LINE);
91 glutAddMenuEntry("BRES_LINE", BRES_LINE);
92 glutAddMenuEntry("CIRCLE_SCAN", CIRCLE);
93
94 // 把菜单和鼠标右键关联起来。
95 glutAttachMenu(GLUT_RIGHT_BUTTON);
96 }
97
98 void DAA_alogrithm(int x0, int y0, int x1, int y1) {
99 int x;
100 float dx, dy, y, k;
101 dx = x1 - x0,dy = y1 - y0;
102 k = dy / dx, y = y0;
103 glPointSize(5.0);
104
105 glBegin(GL_POINTS);
106
107 for (x = x0;x <= x1;x++) {
108
109 glVertex2d(x, int(y + 0.5));
110 y = y + k;
111 }
112 glEnd();
113 }
114 void y_DAA_alogrithm(int x0, int y0, int x1, int y1) {
115 int y;
116 float dx, dy, x, k;
117 dx = x1 - x0, dy = y1 - y0;
118 k = dx / dy, x = x0;
119 glPointSize(5.0);
120
121 glBegin(GL_POINTS);
122
123 for (y = y0;y <= y1;y++) {
124
125 glVertex2d(int(x + 0.5),y );
126 x = x + k;
127 }
128 glEnd();
129 }
130 void Bresenham(int x0, int y0, int x1, int y1) {
131 bool is_nagetive_k = false;
132 if ((y1 - y0) * (x1 - x0) < 0) {
133 y1 *= -1, y0 *= -1;
134 is_nagetive_k = true;
135 }
136 int x, y, dx, dy, e;
137 dx = x1 - x0, dy = y1 - y0,e=-dx;
138 x = x0;y = y0;
139 glPointSize(5.0);
140
141 glBegin(GL_POINTS);
142 for (int i = 0;i < dx;i++) {
143 if (!is_nagetive_k)glVertex2d(x, y);else {
144 glVertex2d(x, -y);
145 }
146 x++, e = e + 2 * dy;
147 if (e >= 0)y++, e = e - 2 * dx;
148 }
149 glEnd();
150 }
151 void y_Bresenham(int x0, int y0, int x1, int y1) {
152 bool is_nagetive_k = false;
153 if ((y1 - y0) * (x1 - x0) < 0) {
154 y1 *= -1;y0 *= -1;
155 is_nagetive_k = true;
156 }
157
158 int x, y, dx, dy, e;
159 dx = x1 - x0, dy = y1 - y0, e = -dy;
160 x = x0;y = y0;
161 glPointSize(5.0);
162
163 glBegin(GL_POINTS);
164 for (int i = 0;i < dy;i++) {
165 if (!is_nagetive_k)glVertex2d(x, y);else {
166 glVertex2d(x, -y);
167 }
168 y++, e = e + 2 * dx;
169 if (e >= 0)x++, e = e - 2 * dy;
170 }
171 glEnd();
172 }
173 void circlePoints(int x,int y) {
174 glPointSize(5.0);
175 glBegin(GL_POINTS);
176 glVertex2d(x,y);glVertex2d(y,x);
177 glVertex2d(-x,y);glVertex2d(-y,x);
178 glVertex2d(x,-y);glVertex2d(y,-x);
179 glVertex2d(-x,-y);glVertex2d(-y,-x);
180 glEnd();
181 }
182 void mindCircle(int r) {
183 int x, y;
184 float d;
185 x = 0;y = r; d = 1.25 - r;
186 circlePoints(x, y);
187 while (x <= y) {
188 if (d < 0) {
189 d += 2 * x + 3;
190 }
191 else {
192 d += 2 * (x - y) + 5;y--;
193 }
194 x++;
195 circlePoints(x, y);
196 }
197 }
198 void display(void)
199 {
200 glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
201 glColor3f(red, green, blue);
202 glLoadIdentity();
203
204
205
206
207 if (MODE == 0) {
208 if (abs(startY - endY) > abs(startX - endX)) {
209 if (startY > endY) {
210 y_DAA_alogrithm(endX, endY,startX, startY);
211 }
212 else {
213 y_DAA_alogrithm(startX, startY, endX, endY);
214 }
215 }
216 else {
217 if (startX > endX) {
218 DAA_alogrithm(endX, endY, startX, startY);
219 }
220 else {
221 DAA_alogrithm(startX, startY, endX, endY);
222 }
223 }
224 }
225 else if (MODE == 1) {
226
227 if (startX > endX) {
228 if (abs(startY - endY) > abs(startX - endX))y_Bresenham(endX, endY, startX, startY);
229 else Bresenham(endX, endY, startX, startY);
230 }
231 else {
232 if(abs(startY - endY) > abs(startX - endX))y_Bresenham(startX, startY, endX, endY);
233 else Bresenham(startX, startY, endX, endY);
234 }
235
236 }
237 else if(MODE==2){
238 glPushMatrix();
239 glTranslated(startX, startY, 0);
240 mindCircle(int(pow((startX - endX) * (startX - endX) + (startY - endY) * (startY - endY), 0.5)));
241 glTranslated(-endX, -endY, 0);
242 glPopMatrix();
243 }
244
245
246
247
248 /*
249 glBegin(GL_LINES);
250
251 glVertex2d(startX, startY);glVertex2d(endX, endY);
252
253 glEnd();
254
255 */
256 /*
257 glPointSize(10.0);
258 for (int i = 0;i < 500;i++) {
259 glVertex2d(100, i);
260 glVertex2d(i, 100);
261 glVertex2d(i, i);
262
263 }
264 glEnd();
265 */
266
267 glutSwapBuffers();
268 }
269 int saveStack = 0;
270 int firstSaveFlag = -1;
271 void keyboard(unsigned char key, int x, int y)
272
273 {
274 switch (key) {
275 case 'q':case 'Q':
276 exit(EXIT_SUCCESS);
277 break;
278 }
279 }
280 int ww, hh;
281
282 void mouse_process(int button, int state, int x, int y)
283 {
284 mouseX = x;
285 mouseY = y;
286 printf("(%d,%d)\n", x, y);
287 printf("(%d,%d)", startX,startY);
288 printf("(%d,%d)\n", endX,endY);
289 hh = glutGet(GLUT_WINDOW_HEIGHT);
290 if (button == GLUT_LEFT_BUTTON)
291 {
292 if (state == GLUT_DOWN)
293 {
294 if (!mouseLeftDown) {
295 startX = x;startY = hh-y;
296 }
297
298 mouseLeftDown = true;
299 }
300 else if (state == GLUT_UP) {
301 mouseLeftDown = false;
302
303 }
304
305 }
306
307 else if (button == GLUT_RIGHT_BUTTON)
308 {
309 if (state == GLUT_DOWN)
310 {
311 mouseRightDown = true;
312 }
313 else if (state == GLUT_UP)
314 mouseRightDown = false;
315 }
316
317
318
319 }
320
321 void mouse_process_active(int x, int y)
322 {
323 if (mouseLeftDown){
324 endX = x;endY = hh - y;
325 glutPostRedisplay();
326 }
327 if(mouseRightDown)
328 {
329
330 }
331 glutPostRedisplay();
332
333 }
334 void mouse_process_passtive(int x, int y) {}
335
336
337 int main(int argc, char** argv)
338 {
339 glutInit(&argc, argv);
340 glutInitDisplayMode(GLUT_RGBA | GLUT_DOUBLE | GLUT_DEPTH);
341 glutInitWindowSize(500, 500);
342 glutCreateWindow("19智能 右键开启菜单");
343
344 init();
345
346 glutDisplayFunc(display);
347
348 // later Edition
349 glutMouseFunc(mouse_process);
350 glutMotionFunc(mouse_process_active);
351 glutPassiveMotionFunc(mouse_process_passtive);
352 createGLUTMenus();
353 glutKeyboardFunc(keyboard);
354 glutMainLoop();
355
356 return 0;
357 }