code_to_genrate_avatar.cpp

/*
g++ filename.cpp -std=c++11
./a.out
display MathPic.ppm
http://blog.csdn.net/xshbx/article/details/45245389
http://www.matrix67.com/blog/archives/6039
*/

#include <iostream>
#include <cmath>
#include <cstdlib>
#define DIM 1024
#define DM1 (DIM-1)
#define _sq(x) ((x)*(x)) // square
#define _cb(x) abs((x)*(x)*(x)) // absolute value of cube
#define _cr(x) (unsigned char)(pow((x),1.0/3.0)) // cube root
 
unsigned char GR(int,int);
unsigned char BL(int,int);
unsigned char BL(int i,int j);

unsigned char RD(int i,int j){  
    // YOUR CODE HERE  
#define LEFT (i < DIM/2)  
#define C1 C(DIM/2, DIM/2, DIM/2)  
#define C2 C(DIM/2, DIM/4, DIM/4)  
    return BL(i, j);  
}  
unsigned char GR(int i,int j){  
    // YOUR CODE HERE  
#define C3 C(DIM/2, 3*DIM/4, DIM/4)  
#define C4 C(DIM/2, DIM/4, DIM/16)  
#define C5 C(DIM/2, 3*DIM/4, DIM/16)  
    return BL(i, j);  
}  
unsigned char BL(int i,int j){  
    // YOUR CODE HERE  
#define C(x, y, r) (_sq(i - (x)) + _sq(j - (y)) < _sq((r)))  
    return !C1 ? 127 : C2 ? C4 ? 0 : 255 : C3 ? C5 ? 255: 0 : LEFT ? 255 : 0;  
}     


void pixel_write(int,int);
FILE *fp;
int main(){
    fp = fopen("MathPic.ppm","wb");
    fprintf(fp, "P6\n%d %d\n255\n", DIM, DIM);
    for(int j=0;j<DIM;j++)
        for(int i=0;i<DIM;i++)
            pixel_write(i,j);
    fclose(fp);
    return 0;
}
void pixel_write(int i, int j){
    static unsigned char color[3];
    color[0] = RD(i,j)&255;
    color[1] = GR(i,j)&255;
    color[2] = BL(i,j)&255;
    fwrite(color, 1, 3, fp);
}