isometric graph paper generator

# -*- coding: UTF-8 -*-
import math
import sys

from reportlab.lib.units import inch

LIB_DIR = './lib'
if not LIB_DIR in sys.path:
    sys.path.insert(0, LIB_DIR)

import PDF

pdf = PDF.PDF('graph_paper.pdf', page_orientation = PDF.PageOrientation.Portrait)

margin = 0.25 * inch

spacing = 0.25 * inch
spacing2 = 0.5 * math.sqrt(3) * spacing

hmargin = 0.5 * math.fmod(pdf.page_width, spacing2)
vmargin = 0.5 * math.fmod(pdf.page_height, spacing)

epsilon = 0.25

for col in range(int(pdf.page_width / spacing2) + 1):
    x = hmargin + col * spacing2

    for row in range(int(pdf.page_height / spacing) + 1):
        if col & 1 == 1:
            y = pdf.page_height - vmargin - row * spacing
        else:
            y = pdf.page_height - vmargin - (row + 0.5) * spacing

        pdf.ellipse(x-epsilon, y-epsilon, x+epsilon, y+epsilon, fill = 1)


pdf.save()