Added backend filament search by similar color

spoolman/math.py

@@ -1,5 +1,7 @@
 """Various math-related functions."""
 
+# ruff: noqa: PLR2004
+
 import math
 
 
@@ -33,3 +35,60 @@ def length_from_weight(*, weight: float, diameter: float, density: float) -> flo
     volume_cm3 = weight / density
     volume_mm3 = volume_cm3 * 1000
     return volume_mm3 / (math.pi * (diameter / 2) ** 2)
+
+
+def rgb_to_lab(rgb: list[int]) -> list[float]:
+    """Convert a RGB color to CIELAB.
+
+    Input is of form [r, g, b] where r, g, and b are integers between 0 and 255.
+    Output is of form [l, a, b] where l, a, and b are floats.
+    """
+    r, g, b = rgb[0] / 255, rgb[1] / 255, rgb[2] / 255
+
+    r = (r / 12.92) if (r <= 0.04045) else math.pow((r + 0.055) / 1.055, 2.4)
+    g = (g / 12.92) if (g <= 0.04045) else math.pow((g + 0.055) / 1.055, 2.4)
+    b = (b / 12.92) if (b <= 0.04045) else math.pow((b + 0.055) / 1.055, 2.4)
+
+    x = (r * 0.4124 + g * 0.3576 + b * 0.1805) / 0.95047
+    y = (r * 0.2126 + g * 0.7152 + b * 0.0722) / 1.00000
+    z = (r * 0.0193 + g * 0.1192 + b * 0.9505) / 1.08883
+
+    x = math.pow(x, 1 / 3) if (x > 0.008856) else (7.787 * x) + 16 / 116
+    y = math.pow(y, 1 / 3) if (y > 0.008856) else (7.787 * y) + 16 / 116
+    z = math.pow(z, 1 / 3) if (z > 0.008856) else (7.787 * z) + 16 / 116
+
+    return [(116 * y) - 16, 500 * (x - y), 200 * (y - z)]
+
+
+def delta_e(lab_a: list[float], lab_b: list[float]) -> float:
+    """Calculate the color difference between two CIELAB colors."""
+    delta_l = lab_a[0] - lab_b[0]
+    delta_a = lab_a[1] - lab_b[1]
+    delta_b = lab_a[2] - lab_b[2]
+    c1 = math.sqrt(lab_a[1] * lab_a[1] + lab_a[2] * lab_a[2])
+    c2 = math.sqrt(lab_b[1] * lab_b[1] + lab_b[2] * lab_b[2])
+    delta_c = c1 - c2
+    delta_h = delta_a * delta_a + delta_b * delta_b - delta_c * delta_c
+    delta_h = math.sqrt(delta_h) if delta_h > 0 else 0
+    sc = 1.0 + 0.045 * c1
+    sh = 1.0 + 0.015 * c1
+    delta_l_kl_sl = delta_l / 1.0
+    delta_c_kc_sc = delta_c / sc
+    delta_h_kh_sh = delta_h / sh
+    i = delta_l_kl_sl * delta_l_kl_sl + delta_c_kc_sc * delta_c_kc_sc + delta_h_kh_sh * delta_h_kh_sh
+    return math.sqrt(i) if i > 0 else 0
+
+
+def hex_to_rgb(hex_code: str) -> list[int]:
+    """Convert a hex color code to RGB.
+
+    Input is of form #RRGGBB where RR, GG, and BB are hexadecimal numbers.
+    Output is of form [r, g, b] where r, g, and b are integers between 0 and 255.
+    """
+    hex_code = hex_code.lstrip("#")
+
+    r = int(hex_code[0:2], 16)
+    g = int(hex_code[2:4], 16)
+    b = int(hex_code[4:6], 16)
+
+    return [r, g, b]