Initial shitty commit of skew-T chart rendering

lib/xmet/skew_t.py

@@ -0,0 +1,194 @@
+#! /usr/bin/env python3
+
+import math
+import cairo
+
+IMAGE_WIDTH  = 1366
+IMAGE_HEIGHT = 768
+
+GRAPH_HEIGHT = IMAGE_HEIGHT - 64
+GRAPH_WIDTH  = (GRAPH_HEIGHT / 10.0) * 18
+
+GRAPH_OFFSET_X = (IMAGE_WIDTH - GRAPH_WIDTH) / 2
+GRAPH_OFFSET_Y = 32
+
+PRESSURE_MAX  = 1050
+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
+TEMP_STEP_WIDTH = GRAPH_HEIGHT / 10.0
+
+ADIABATIC_LAPSE_RATE_DRY   = 9.8 / 1000 # degrees C per 1000m
+ADIABATIC_LAPSE_RATE_MOIST = 4.0 / 1000
+
+def clamp(value, lowest, highest):
+    if value < lowest:
+        return lowest
+    elif value > highest:
+        return highest
+
+    return value
+
+def pressure_y(pressure: float) -> float:
+    if pressure < PRESSURE_MIN:
+        pressure = PRESSURE_MIN
+    elif pressure > PRESSURE_MAX:
+        pressure = PRESSURE_MAX
+
+    log_p  = math.log(pressure)
+    factor = (PRESSURE_LOG_MAX - log_p) / PRESSURE_LOG_RANGE
+
+    return factor * GRAPH_HEIGHT
+
+def graph_to_screen(x, y) -> tuple:
+    return (
+        GRAPH_OFFSET_X + x,
+        IMAGE_HEIGHT - GRAPH_OFFSET_Y - y
+    )
+
+def draw_pressure_lines(cr: cairo.Context):
+    for pressure in range(PRESSURE_MIN, PRESSURE_MAX+1, PRESSURE_STEP):
+        (x, y) = graph_to_screen(0, pressure_y(pressure))
+
+        cr.set_source_rgba(0.0, 0.0, 0.0, 0.5)
+        cr.move_to(x, y)
+        cr.rel_line_to(GRAPH_WIDTH, 0)
+        cr.stroke()
+
+def draw_graph_line(cr: cairo.Context, x1, y1, x2, y2):
+    (screen_x1, screen_y1) = graph_to_screen(x1, y1)
+    (screen_x2, screen_y2) = graph_to_screen(x2, y2)
+
+    cr.move_to(screen_x1, screen_y1)
+    cr.line_to(screen_x2, screen_y2)
+    cr.stroke()
+
+ISOTHERM_LINES = (
+    (0, 0, 9, 9), (1, 0, 9, 8), (2, 0, 9, 7), (3, 0, 9, 6),
+    (4, 0, 9, 5), (5, 0, 9, 4), (6, 0, 9, 3), (7, 0, 9, 2),
+    (8, 0, 9, 1), (9, 0, 9, 0),
+
+    (-1, 0, 9, 10), (-2, 0, 8, 10), (-3, 0, 7, 10), (-4, 0, 6, 10),
+    (-5, 0, 5, 10), (-6, 0, 4, 10), (-7, 0, 3, 10), (-8, 0, 2, 10),
+    (-9, 0, 1, 10),
+
+    (-9, 1,  0, 10), (-9, 2, -1, 10), (-9, 3, -2, 10),
+    (-9, 4, -3, 10), (-9, 5, -4, 10), (-9, 6, -5, 10),
+    (-9, 7, -6, 10), (-9, 8, -7, 10), (-9, 9, -8, 10),
+)
+
+def isotherm_to_graph(x, y) -> tuple:
+    return (
+        GRAPH_WIDTH / 2 + x,
+        y
+    )
+
+def draw_isotherms(cr: cairo.Context):
+    cr.set_source_rgba(0.1, 0.5, 0.1, 0.8)
+
+    for line in ISOTHERM_LINES:
+        x1 = line[0] * TEMP_STEP_WIDTH
+        y1 = line[1] * TEMP_STEP_WIDTH
+        x2 = line[2] * TEMP_STEP_WIDTH
+        y2 = line[3] * TEMP_STEP_WIDTH
+
+        graph_1 = isotherm_to_graph(x1, y1)
+        graph_2 = isotherm_to_graph(x2, y2)
+
+        draw_graph_line(cr, graph_1[0], graph_1[1], graph_2[0], graph_2[1])
+
+def sample_to_graph(temp: float, pressure: float):
+    x = (temp / TEMP_STEP) * TEMP_STEP_WIDTH
+    y = pressure_y(pressure)
+
+    return (
+        GRAPH_WIDTH / 2 + x + y,
+        y
+    )
+
+SAMPLES = (
+    (    101200, -6),
+    (    101200,   -6),
+    (    100000,  -12),
+    (    99300,  -22),
+    (    98700,  -29),
+    (    97500,  -39),
+    (    95700,  -50),
+    (    95100,  -47),
+    (    93900,  -43),
+    (    92000,  -34),
+    (    90400,  -34),
+    (    90000,  -34),
+    (    89200,  -34),
+    (    85000,  -34),
+    (    83700,  -34),
+    (    82100,  -34),
+    (    80000,  -42),
+    (    78600,  -46),
+    (    77600,  -50),
+    (    70000,  -77),
+    (    69100,  -80),
+    (    60700, -128),
+    (    60000, -133),
+    (    53100, -186),
+    (    50000, -215),
+    (    46300, -255),
+    (    40200, -337),
+    (    40000, -340),
+    (    35000, -412),
+    (    34900, -413),
+    (    30100, -496),
+    (    30000, -496),
+    (    25700, -565),
+    (    25000, -577),
+    (    24400, -585),
+    (    22100, -510),
+    (    21900, -510),
+    (    20000, -497),
+    (    15000, -466),
+    (    10000, -438),
+    (    7000, -414),
+    (    5000, -393),
+    (    3000, -368),
+    (    2000, -344),
+    (    1500, -337),
+    (    1000, -305),
+    (    500, -210),
+    (    400, -198)
+)
+
+with cairo.SVGSurface('test.svg', IMAGE_WIDTH, IMAGE_HEIGHT) as surface:
+    cr = cairo.Context(surface)
+
+    cr.rectangle(GRAPH_OFFSET_X, GRAPH_OFFSET_Y, GRAPH_WIDTH, GRAPH_HEIGHT)
+    cr.stroke()
+
+    draw_pressure_lines(cr)
+    draw_isotherms(cr)
+
+    cr.set_source_rgb(0, 0, 1)
+
+    first = True
+
+    for sample in SAMPLES:
+        pressure = sample[0] / 100.0
+        temp     = sample[1] * 0.1
+
+        gx, gy = sample_to_graph(temp, pressure)
+        x,  y  = graph_to_screen(gx, gy)
+
+        print(f"x {x} y {y} pressure {pressure} temp {temp}")
+
+        if first:
+            cr.move_to(x, y)
+            first = False
+        else:
+            cr.line_to(x, y)
+
+    cr.stroke()