#include <stdlib.h>
#include <string.h>
#include <math.h>
typedef struct {
size_t width;
size_t height;
unsigned char *data;
} Image;
static Image *image_new (size_t width,size_t height){
Image *image;
image = malloc (sizeof *image);
image->width = width;
image->height = height;
image->data = malloc (width * height);
return image;
}
static void image_free (Image *image){
free (image->data);
free (image);
}
static void image_fill (Image *image,unsigned char value){
memset (image->data, value, image->width * image->height);
}
/**
* image_set_pixel:
* Sets a pixel passed in signed (x, y) coordinates, where (0,0) is at
* the center of the image.
**/
static void image_set_pixel(Image *image,
ssize_t x,
ssize_t y,
unsigned char value){
size_t tx, ty;
unsigned char *p;
tx = (image->width / 2) + x;
ty = (image->height / 2) + y;
p = image->data + (ty * image->width) + tx;
*p = value;
}
static void image_save (const Image *image,
const char *filename){
FILE *out;
out = fopen (filename, "wb");
if (!out)
return;
fprintf (out, "P5\n");
fprintf (out, "%zu %zu\n", image->width, image->height);
fprintf (out, "255\n");
fwrite (image->data, 1, image->width * image->height, out);
fclose (out);
}
static void draw_Taijitu(Image *image,int radius,int value){
int x,y;
int rlimit ,llimit;
int radius_2 = radius*radius;
for(y = -radius;y<radius;y++)
for(x= -radius;x<radius;x++)
if(x*x+y*y <= radius_2)//画圆
image_set_pixel(image,x,y,0xff);//填充白色
for(y=-radius;y<0;y++)
for(x = 0;x<radius;x++)//
if((x*x)+(y*y) <= radius_2)//四分之一圆
image_set_pixel(image,x,y,value); // 黑色
for( x = -(int)sqrt((double)(-radius*y-y*y)); x<0; x++)//
image_set_pixel(image,x,y,value);//
for(y=0;y<radius;y++){
llimit = (int)sqrt((double)(radius*y - y*y));
rlimit = (int)sqrt((double)(radius_2 - y*y));
for(x = llimit;x<rlimit;x++)
image_set_pixel(image,x,y,value);//黑色
}
rlimit =(int) sqrt((double)(radius*y-y*y-2*radius_2/9));
llimit = -rlimit;
for(x = llimit;x<rlimit;x++)
image_set_pixel(image,x,y,value);
}
for(y = -4*radius/6;y<-2*radius/6;y++){//下方
rlimit = sqrt(-radius*y-y*y-2*radius_2/9);
llimit = -rlimit;
for(x = llimit;x<rlimit;x++)
image_set_pixel(image,x,y,0xff);
}
}
int main(int argc, char *argv[]){
Image *image;
image = image_new (800, 800);//创建一个文件空间
image_fill (image, 0xaa); //填充背景色
draw_Taijitu (image, 300, 0);//画半径为300的太极图
image_save (image, "taiji_6.pgm");//生成文件并保存
image_free (image);//释放文件空间
return 0;
}
参阅：http://blog.chinaunix.net/uid-24774106-id-3048064.html