#! /usr/bin/env python

# gauge-png.py: create a gauge faceplate for the Asia Engineer 30 volt round
# analog panel meter.

# copyright 2008 jason pepas (jason@pepas.com)
# distributed under the terms of the GNU General Public License, version 2
# see http://www.gnu.org/copyleft/gpl.html

# changelog:
#
# 0.1 (2008/1/5)
#  * initial release.
#  * basic faceplate mask.
#  * dimensions conform to original faceplate.

from math import pi
import cairo

# tunables:
width = 600
height = 600
bottom_edge = 0.875
needle_hole_radius = 0.175
needle_hole_y_offset = 0.2125
backlight_radius = 0.525
backlight_thickness = 0.0875

# you shouldn't need to tune these.
outer_radius = 0.5
center_x = 0.5
center_y = 0.5
needle_hole_center_x = center_x
needle_hole_center_y = center_y + needle_hole_y_offset
backlight_radian_start = -(pi * (3/4.0))
backlight_radian_end = backlight_radian_start + (pi/2)

# cairo init
surface = cairo.ImageSurface(cairo.FORMAT_ARGB32, width, height)
cr = cairo.Context(surface)

# set up a transform so that 1.0 is full width/height
cr.scale(width/1.0, height/1.0)

# white background
cr.set_source_rgb(1.0, 1.0, 1.0)
cr.rectangle(0, 0, width, height)
cr.fill()

# we will use subtractive geometry.  start with a big black disc and then
# remove the bits we don't want.

# 1: circle
cr.set_source_rgb(0.0, 0.0, 0.0)
cr.arc(center_x, center_y, outer_radius, 0, 2 * pi)
cr.fill()

# 2: bottom square
cr.set_source_rgb(1.0, 1.0, 1.0)
cr.rectangle(0, bottom_edge, 1, 1)
cr.fill()

# 3: needle hole circle
cr.set_source_rgb(1.0, 1.0, 1.0)
cr.arc(needle_hole_center_x, needle_hole_center_y, needle_hole_radius, 0, 2 * pi)
cr.fill()

# 4: bottom entry way for needle assembly
cr.set_source_rgb(1.0, 1.0, 1.0)
cr.rectangle(center_x - needle_hole_radius, needle_hole_center_y, needle_hole_radius*2, 1)
cr.fill()

# 5: backlight arc-hole
cr.set_source_rgb(1.0, 1.0, 1.0)
cr.arc(needle_hole_center_x, needle_hole_center_y, backlight_radius, backlight_radian_start, backlight_radian_end)
cr.set_line_width(backlight_thickness)
cr.stroke()

# dump to file
surface.write_to_png("mask.png")