#! /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.
#
# 0.2 (2008/1/5)
#  * tick marks!

from math import pi
import cairo

# tunables:
width = 600
height = width
bottom_edge = 0.875
needle_hole_radius = 0.175
needle_hole_y_offset = 0.2125
backlight_radius = 0.525
backlight_arc_height = 0.0875
primary_divisions = 5
secondary_divisions = 10

# 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)

def draw_basic_mask(cr):
    # 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)
    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_arc_height)
    cr.stroke()

def draw_tick_mark(tick_offset, tick_width, tick_height):
    #these are actually implemented as very short and stubby arcs.
    cr.set_source_rgb(0, 0, 0)
    cr.arc(needle_hole_center_x, \
        needle_hole_center_y, \
        backlight_radius + (backlight_arc_height/2) - ((backlight_arc_height*tick_height)/2), \
        backlight_radian_start + (tick_offset*(pi/2)) - ((tick_width*(pi/2))/2), \
        backlight_radian_start + (tick_offset*(pi/2)) + ((tick_width*(pi/2))/2))
    cr.set_line_width(backlight_arc_height * tick_height)
    cr.stroke()

def draw_ticks(primary_divisions, secondary_divisions):
    # first draw the primary ticks
    primary_ticks = primary_divisions + 1
    primary_tick_width = 0.01
    primary_tick_height = 2 / 3.0
    for i in range(0, primary_ticks):
        tick_offset = i / float(primary_ticks - 1)
        draw_tick_mark(tick_offset, primary_tick_width, primary_tick_height)

    # now draw the secondary ticks
    secondary_tick_width = primary_tick_width / 2.0
    secondary_tick_height = primary_tick_height / 2.0
    for i in range(0, ((primary_ticks - 1) * secondary_divisions) + 1):
        tick_offset = i / float(((primary_ticks - 1) * secondary_divisions))
        draw_tick_mark(tick_offset, secondary_tick_width, secondary_tick_height)

if __name__ == '__main__':
    # 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)
    
    # start with the basic mask
    draw_basic_mask(cr)

    # now for some tick marks.
    draw_ticks(primary_divisions, secondary_divisions)
    
    # dump to file
    surface.write_to_png("mask.png")