Logistic Map 

Source Link
 1 #include <stdio.h>
 2 #include <stdlib.h>
 3 #include <math.h>
 4 
 5 #define X 2560  //尽量为8的倍数，若不是X/8需向上取整
 6 #define Y 1600  //推荐X、Y比例为(4.0-2.4):1，这样网格为正方形
 7 
 8 
 9 #define b_start 2.4
10 #define b_end 4.0
11 #define b_len (b_end-b_start)
12 
13 #define PI 3.14159265358979323846
14 #define function(_b, _x) (_b*sin(_x*PI)/4)
15 //迭代方程  
16 //x = b*x*(1-x) (_b*_x*(1-_x))
17 //x = b/4*sin(x/pi) (_b*sin(_x*PI)/4)
18 int main(int argc, char **argv)
19 {
20     double x;
21     if(argc==2)
22         x = atof(argv[1]);
23     else
24         x = 0.6;
25 
26     unsigned char * data = (unsigned char *)calloc(X*Y/8, 1);
27     
28     double b = b_start;
29     for(int i=0;i<X;i++){   //保证x轴取点密度
30         double temp = x;
31         for(int k=0;k<4000;k++){    //先迭代至基本稳定
32             temp = function(b, temp);
33         }
34         for(int k=0;k<1000;k++){    //真正画的部分
35             temp = function(b, temp);
36             int vx = (b-b_start)/b_len*X;   //visual(virtual) x
37             int vy = temp*Y;                //visual(virtual) y
38             data[(Y-1-vy)*(X/8)+vx/8] |= 1<<(7-vx%8);
39         }
40         b += b_len/X;
41     }
42     //画竖线
43     for(double i=b_start;i<b_end;i+=0.1){
44         int vx = (i-b_start)/b_len*X;   //visual(virtual) x
45         for(int vy=0;vy<Y;vy++){
46             data[(Y-1-vy)*(X/8)+vx/8] |= 1<<(7-vx%8);
47         }
48     }
49     //画横线
50     for(double i=0;i<1;i+=0.1){
51         int vy = i*Y;                   //virsual(virtual) y  
52         for(int vx=0;vx<X;vx++){
53             data[(Y-1-vy)*(X/8)+vx/8] |= 1<<(7-vx%8);
54         }
55     }
56     //图片输出
57     FILE *fp;
58     fp = fopen("0.25 sin(PI x).pbm","wb");
59     fprintf(fp, "P4 %d %d\n", X, Y);
60     for(int i=0; i<X*Y/8; i++)
61         fputc(data[i], fp);
62     fclose(fp);
63     
64     free(data);
65     return 0;
66 }

Demo

x = b * x * (1 - x)


x = b / 4 * sin(PI * x)

 

posted on 2022-08-21 12:56  acd407  阅读(95)  评论(0)    收藏  举报

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