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XANTRONIX 2025-02-23 17:12:58 -05:00
parent d5294e111d
commit b818671816
1 changed files with 30 additions and 2 deletions
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32
lib/xmet/skew_t.py
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@ -1,6 +1,14 @@
import math
import cairo
PRESSURE_MAX = 1050 # millibar
PRESSURE_MIN = 100
PRESSURE_STEP = 50
PRESSURE_LOG_MAX = math.log(PRESSURE_MAX)
PRESSURE_LOG_MIN = math.log(PRESSURE_MIN)
PRESSURE_LOG_RANGE = PRESSURE_LOG_MAX - PRESSURE_LOG_MIN
TEMP_CENTER = 0 # degrees C
TEMP_STEP = 5
@ -38,8 +46,27 @@ class SkewT():
def graph_to_screen(self, x, y) -> tuple:
return (self.width / 2) + x, self.height - y
def draw_pressure_lines(self, cr: cairo.Context):
pass
def pressure_y(self, pressure: float) -> float:
log_p = math.log(clamp(pressure, PRESSURE_MIN, PRESSURE_MAX))
factor = (PRESSURE_LOG_MAX - log_p) / PRESSURE_LOG_RANGE
return factor * self.height
def sample_to_graph(self, temp: float, pressure: float):
x = (temp / TEMP_STEP) * self.temp_step_width
y = self.pressure_y(pressure)
return x + y, y
def draw_pressure_lines(self, cr: cairo.Context, x: float, y: float):
for pressure in range(PRESSURE_MIN, PRESSURE_MAX+1, PRESSURE_STEP):
coord = self.graph_to_screen(-self.width / 2,
self.pressure_y(pressure))
cr.set_source_rgba(0, 0, 0, 0.5)
cr.move_to(x + coord[0], y + coord[1])
cr.rel_line_to(self.width, 0)
cr.stroke()
def draw_isotherms(self, cr: cairo.Context, x: float, y: float):
cr.set_source_rgba(0.1, 0.5, 0.1, 0.8)
@ -59,3 +86,4 @@ class SkewT():
def draw(self, cr: cairo.Context, x: float, y: float):
self.draw_isotherms(cr, x, y)
self.draw_pressure_lines(cr, x, y)