======Shapes in GD: Circle======

Even though GD has the ability to draw arcs, sometimes it is preferable to render them manually, in order to gain additional functionality. This example will do just that.

=====code=====

Please type this in, do not copy and paste, and ask questions along the way:

====Part 1====

<code c>
#include <stdio.h>
#include <gd.h>
#include <math.h>

#define PI          3.1415926535897

int main()
{
    FILE *out;
    char outfile[] = "image.png";
    gdImagePtr         img;    
    unsigned int       current;
    unsigned short int wide, high;
    int degree, x, y, r = 0, red = 0, green = 0, blue = 0;
    float radian; 

    wide = 800;
    high = 800;

    img = gdImageCreate(wide, high);

    current = gdImageColorAllocate(img, 0x00, 0x00, 0x00);
    gdImageFilledRectangle(img, 0, 0, wide, high, current);
</code>

This sets us up and gets us a clean slate.

====Part 2====
This part will do the actual grunt work chugging out a circle (using units of squares):

<code c>
    r = 200;
    green = 0xFF; 
    for(degree = 0; degree < 360; degree++)
    {
        radian = degree * (PI / 180); 
        x = (wide / 2) + r * sin(radian);
        y = (high / 2) + r * cos(radian);
        current = gdImageColorAllocate(img, 0, green, 0);
        gdImageFilledRectangle(img, x, y, x+20, y+20, current);
    }
</code>

====Part 3====
And close everything up nicely:

<code c>
    // Output the data
    //
    out = fopen(outfile, "wb");
    gdImagePngEx(img, out, -1);

    // Close things up
    //
    fclose(out);
    gdImageDestroy(img);

    return(0);
}
</code>

=====To compile=====
Since we're using both the math and GD libraries, don't forget to link against them:

<cli>
lab46:~/src/gdstuff$ gcc -o circle circle.c -lm -lgd
</cli>

This will once again produce an image file that will have to be viewed using an appropriate program.