def _calc_pixel_dimensions(self, pixel_dimensions):
""" Calculate the size of the image in pixels, given whatever
minimum / maximums we've been given.
"""
if pixel_dimensions is None or len(pixel_dimensions.keys()) == 0:
pixel_dimensions = {"max": DEFAULT_SIZE}
if "width" in pixel_dimensions and "height" in pixel_dimensions:
self.pixel_width = pixel_dimensions["width"]
self.pixel_height = pixel_dimensions["height"]
return
self.aspect_ratio = (self.max_longitude - self.min_longitude) / \
(mercator_adjust(self.max_latitude) -
mercator_adjust(self.min_latitude))
if "width" in pixel_dimensions:
self.pixel_width = pixel_dimensions["width"]
self.pixel_height = int(float(self.pixel_width) / self.aspect_ratio)
return
if "height" in pixel_dimensions:
self.pixel_height = pixel_dimensions["height"]
self.pixel_width = int(float(self.pixel_height) * self.aspect_ratio)
return
if "max" in pixel_dimensions:
if self.aspect_ratio > 1:
self.pixel_width = pixel_dimensions["max"]
self.pixel_height = int(float(self.pixel_width) /
self.aspect_ratio)
return
self.pixel_height = pixel_dimensions["max"]
self.pixel_width = int(float(self.pixel_height) * self.aspect_ratio)
return
if "min" in pixel_dimensions:
if self.aspect_ratio < 1:
self.pixel_width = pixel_dimensions["min"]
self.pixel_height = int(float(self.pixel_width) /
self.aspect_ratio)
return
self.pixel_height = pixel_dimensions["min"]
self.pixel_width = int(float(self.pixel_height) * self.aspect_ratio)
return
raise ValueError("Could not calculate the image resolution")
def _convert_to_fraction(self, point):
""" Convert a lat/long point into an (x,y) fraction of the drawing area
"""
# TODO: this could be neater. The addition / subtraction should
# be (a) consistently one or the other, and (b) we should adjust
# the image width to take it into account.
# Add half a pixel width so that we're drawing in the centre of
# a pixel, not on the edge
x = 0.5 / self.pixel_width + (point.long - self.min_longitude) / \
(self.max_longitude - self.min_longitude)
merc_lat = mercator_adjust(point.lat)
# Subtract half a pixel width so that we're drawing in the
# centre of a pixel, not on the edge
y = 1 - (0.5 / self.pixel_height) - \
(merc_lat - self.min_merc_latitude) / self.merc_latitude_width
return (x, y)
