diagram.py

from svg import Svg
import codecs

MARGIN_X=20
MARGIN_Y=60
MAGNIFICATION = 500

MIN_D = 1
MAX_D = 4

DIMMEST_MAG = 6
BRIGHTEST_MAG = -1.5

LABEL_OFFSET_X = 4
LABEL_OFFSET_Y = 3
FONT_SIZE=16
FONT_COLOUR='#167ac6'

TITLE_SIZE=16
TITLE_COLOUR='#000'
COORDS_SIZE=12
COORDS_COLOUR='#000'

STAR_COLOUR='#000'

CURVE_WIDTH = 0.1
CURVE_COLOUR = '#000'

class Diagram:
    def __init__(self, title, area, star_data_list):
        self.title = title
        self.area = area
        self.star_data_list = star_data_list
        self.curves = []
        self.border_min_x = self.border_min_y = self.border_max_x = self.border_max_y = None

    def add_curve(self, curve_points):
        self.curves.append(curve_points)

    def _mag_to_d(self, m):
        mag_range = DIMMEST_MAG - BRIGHTEST_MAG
        m_score = (DIMMEST_MAG - m) / mag_range
        r_range = MAX_D - MIN_D
        return MIN_D + m_score * r_range

    def _invert_and_offset(self, x, y):
        return x + MARGIN_X, (self.star_data_list.max_y - y) + MARGIN_Y

    def render_svg(self, outfile):
        svg = Svg()

        # add stars first
        for star_data in self.star_data_list.data:
            x, y = self._invert_and_offset(star_data.x, star_data.y)
            svg.circle(x, y, self._mag_to_d(star_data.mag), STAR_COLOUR)

        # next add labels
        for star_data in self.star_data_list.data:
            if star_data.label:
                x, y = self._invert_and_offset(star_data.x, star_data.y)
                d = self._mag_to_d(star_data.mag)
                svg.text(x + LABEL_OFFSET_X + d/2, y + LABEL_OFFSET_Y, star_data.label, FONT_COLOUR, FONT_SIZE)

        # next add curves
        for curve_points in self.curves:
            svg.curve([self._invert_and_offset(cp[0], cp[1]) for cp in curve_points], CURVE_WIDTH, CURVE_COLOUR)

        # title
        center_x = self.star_data_list.max_x/2 + MARGIN_X
        svg.text(center_x, MARGIN_Y/2, self.title, TITLE_COLOUR, TITLE_SIZE, 'middle', 'underline')

        # coords
        chart_bottom_y = self.star_data_list.max_y + MARGIN_Y
        svg.text(center_x, chart_bottom_y + MARGIN_Y/2, "Right Ascension: {}-{}".format(self.area.ra_min, self.area.ra_max), COORDS_COLOUR, COORDS_SIZE, 'middle')
        svg.text(center_x, chart_bottom_y + MARGIN_Y/2 + COORDS_SIZE, "Declination: {}-{}".format(self.area.dec_min, self.area.dec_max), COORDS_COLOUR, COORDS_SIZE, 'middle')

        codecs.open(outfile, 'w', 'utf-8').writelines(svg.to_list())