128 lines
3.7 KiB
Python
128 lines
3.7 KiB
Python
import math
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import cairo
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from typing import Iterable, Callable
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from xmet.sounding import SoundingSample
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PRESSURE_MAX = 1050 # millibar
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PRESSURE_MIN = 100
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PRESSURE_STEP = 50
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PRESSURE_LOG_MAX = math.log(PRESSURE_MAX)
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PRESSURE_LOG_MIN = math.log(PRESSURE_MIN)
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PRESSURE_LOG_RANGE = PRESSURE_LOG_MAX - PRESSURE_LOG_MIN
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TEMP_MAX = 60
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TEMP_MIN = -40
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TEMP_RANGE = TEMP_MAX - TEMP_MIN
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TEMP_CENTER = 0 # degrees C
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TEMP_STEP = 5
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TEMP_STEP_COUNT = math.ceil(TEMP_RANGE / TEMP_STEP)
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def clamp(value, lowest, highest):
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if value < lowest:
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return lowest
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elif value > highest:
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return highest
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return value
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class SkewTGraph():
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__slots__ = 'width', 'height', 'temp_step_width',
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def __init__(self, width: float, height: float):
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self.width = width
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self.height = height
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self.temp_step_width = min(self.width, self.height) / TEMP_STEP_COUNT
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def graph_to_screen(self, x, y) -> tuple:
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return (self.width / 2) + x, self.height - y
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def pressure_y(self, pressure: float) -> float:
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log_p = math.log(clamp(pressure, PRESSURE_MIN, PRESSURE_MAX))
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factor = (PRESSURE_LOG_MAX - log_p) / PRESSURE_LOG_RANGE
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return factor * self.height
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def draw_isobars(self, cr: cairo.Context, x: float, y: float):
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cr.set_source_rgb(0.5, 0.5, 0.5)
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for pressure in range(PRESSURE_MIN, PRESSURE_MAX+1, PRESSURE_STEP):
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coord = self.graph_to_screen(-self.width / 2,
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self.pressure_y(pressure))
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cr.set_source_rgba(0, 0, 0, 0.5)
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cr.move_to(x + coord[0], y + coord[1])
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cr.rel_line_to(self.width, 0)
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cr.stroke()
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def skew_t_to_graph(self, x: float, y: float):
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return (x+y, y)
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def sample_to_graph(self, temp: float, pressure: float):
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x = (temp / TEMP_STEP) * self.temp_step_width
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y = self.pressure_y(pressure)
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return self.skew_t_to_graph(x, y)
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def draw_isotherms(self, cr: cairo.Context, x: float, y: float):
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cr.set_source_rgb(0.95, 0.95, 0.95)
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for temp in range(-150, TEMP_MAX+1, TEMP_STEP):
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x1, y1 = self.graph_to_screen(*self.sample_to_graph(temp, PRESSURE_MAX))
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x2, y2 = self.graph_to_screen(*self.sample_to_graph(temp, PRESSURE_MIN))
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cr.move_to(x + x1, y + y1)
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cr.line_to(x + x2, y + y2)
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cr.stroke()
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def draw_samples(self,
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cr: cairo.Context,
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x: float,
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y: float,
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samples: Iterable[SoundingSample],
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fn: Callable):
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first = True
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for sample in samples:
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if sample.pressure < PRESSURE_MIN:
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break
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#
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# Temperature may possibly be dewpoint, depending on the
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# return value of the callback.
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#
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temp = fn(sample)
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if temp is None:
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continue
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gx, gy = self.sample_to_graph(temp, sample.pressure)
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sx, sy = self.graph_to_screen(gx, gy)
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if first:
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cr.move_to(x + sx, y + sy)
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first = False
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else:
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cr.line_to(x + sx, y + sy)
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cr.stroke()
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def draw(self,
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cr: cairo.Context,
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x: float,
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y: float,
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samples: Iterable[SoundingSample]):
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cr.rectangle(x, y, self.width, self.height)
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cr.clip()
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self.draw_isotherms(cr, x, y)
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self.draw_isobars(cr, x, y)
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cr.set_source_rgb(1, 0, 0)
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self.draw_samples(cr, x, y, samples, lambda s: s.temp)
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cr.set_source_rgb(0, 1, 0)
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self.draw_samples(cr, x, y, samples, lambda s: s.dewpoint)
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