main.go

package main
import ("./canvas";
        "os";
        "math";
        "syscall";
        "image/png";
        "fmt";
)

func main() {
	img       := canvas.EmptyCanvasImage(320, 240, canvas.Color32(0xffffffff));
	drawTestPattern(img);

	outfile,e := outputFile("./out.png");
	if e == nil {
		png.Encode(outfile, img);
	}
	 
	fmt.Printf("done\n");
	outfile.Close();
}

func drawTestPattern(img *canvas.CanvasImage) {
	kr := uint32(255);
	kb := uint32(0);

	cx := img.Width()/2;
	cy := img.Height()/2;
	var ox, oy, x, y int;
	for a := 0;a <= 360;a++ {
		ox = x;	
		oy = y;	
		
		r  := float64(a) * 0.0174533;
		rf := math.Sin(r*6.0);
		x = cx + int(math.Sin(r) * 90.0*rf);
		y = cy + int(math.Cos(r) * 90.0*rf);
		if a==0 {continue;}

		img.DrawLine(ox, oy, x, y, canvas.Color32(0xff008800 | (kr<<16) | (kb)));
		
		if 0 != (a&1) {
			kr--;
			kb++;
		}
	}
}

type OutFile struct {
	fd int;
}

func outputFile(name string) (file *OutFile, err os.Error)
{
	fd, e := syscall.Open(name, syscall.O_CREAT|syscall.O_WRONLY, 0766);
	if e==0 {
		f := new(OutFile);
		f.fd = fd;
		return f, nil;
	}
	
	return nil, os.Errno(e);
}

func (f *OutFile) Write(b []byte) (ret int, err os.Error) {
	if f == nil {
		return -1, os.EINVAL;
	}

	r, e := syscall.Write(f.fd, b);
	if e != 0 {
		err = os.Errno(e);
	}
	return int(r), err
}

func (f *OutFile) Close() os.Error {
	if f == nil {
		return os.EINVAL
	}
	
	e := syscall.Close(f.fd);
	f.fd = -1;
	if e != 0 {
		return os.Errno(e);
	}
	return nil
}