from reportlab.pdfgen import canvas
from reportlab.lib.units import mm

OUTPUT = "grid.pdf"
width, height = (181.7 * mm, 256.8 * mm)
GRID_COLOR = (0.5, 0.5, 1)
INTERVAL = 5 * mm

numv = int((width - ((4 + 4) * mm)) / INTERVAL)
numh = int((height - (16 + 3) * mm) / INTERVAL)
voff = (width - numv * INTERVAL) / 2.0
hoff = 16 * mm

# Draw
c = canvas.Canvas(OUTPUT, pagesize=(width, height))
c.setLineWidth(0.15)
c.setStrokeColorRGB(*GRID_COLOR)
for xi in xrange(numv + 1):
    c.line(xi * INTERVAL + voff, hoff,
           xi * INTERVAL + voff, hoff + numh * INTERVAL)
for yi in xrange(numh + 1):
    c.line(voff, hoff + yi * INTERVAL,
           voff + numv * INTERVAL, hoff + yi * INTERVAL)

#c.circle(width / 2, 5 * mm, 0.7, fill=1)
c.save()