# This file is part of pelagos_py.
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# Copyright 2025-2026 National Oceanography Centre and The Contributors
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
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#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
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"""Shared per-variable colour palettes for pelagos_py plots.
Single source of truth for the colourmaps used across the toolbox. Each entry is
a list of hex stops ordered low -> high value; ``get_cmap`` builds a matplotlib
``LinearSegmentedColormap`` from one.
"""
# Per-variable sequential palettes, keyed by lower-case name; stops low -> high.
SEQUENTIAL = {
"temperature": [
"#1b1c6e", "#365292", "#5286b7", "#8db4c4", "#dbe5cd",
"#f1d8b4", "#d9997e", "#c05e4c", "#a0372b", "#811910",
],
"salinity": [
"#f9e8b1", "#f1c38f", "#e8a074", "#db7c5f", "#cb5c58",
"#b2425c", "#943061", "#732460", "#511c53", "#321340",
],
"density": [
"#e6f1f7", "#c4d8e8", "#a6bed9", "#8ba4c9", "#7489b8", "#636c9f",
"#595388", "#55406e", "#4e3055", "#3f2040", "#2e1226",
],
"oxygen": [
"#eaf85a", "#f5d848", "#fbba3e", "#fb9e3e", "#f4844c", "#e4725f",
"#ca6774", "#af5f82", "#95568a", "#7c4d90", "#634198", "#4735a0",
"#203487", "#0a2f59", "#313335",
],
"chlorophyll": [
"#182548", "#2c5398", "#4a88a4", "#87b8b5", "#dae4da",
"#e6d992", "#a8ab3e", "#56872e", "#285932", "#1b2617",
],
"backscatter": [
"#cccccc", "#737373", "#000000", "#1335f5", "#3f8df7",
"#67dffb", "#a1fc4e", "#f8d748", "#ef8733", "#ea3323",
],
# cmocean "solar" sampled to hex (dark maroon -> bright yellow), for PAR.
"solar": [
"#331318", "#4d1c1a", "#6a2517", "#862f13", "#9c3d13", "#ad5017",
"#bb641c", "#c67c24", "#cf9730", "#d4b445", "#d3d55e",
],
}
# Dataset variable names -> SEQUENTIAL palette key.
VARIABLE_PALETTES = {
"TEMP": "temperature",
"CONS_TEMP": "temperature",
"PSAL": "salinity",
"PRAC_SALINITY": "salinity",
"ABS_SALINITY": "salinity",
"DENSITY": "density",
"SIGMA0": "density",
"DOXY": "oxygen",
"CHLA": "chlorophyll",
"CHLA_ADJUSTED": "chlorophyll",
"BBP700": "backscatter",
"BBP700_ADJUSTED": "backscatter",
}
[docs]
def get_cmap(name):
"""Build a matplotlib colormap from a named SEQUENTIAL palette (case-insensitive)."""
from matplotlib.colors import LinearSegmentedColormap
key = name.lower()
if key not in SEQUENTIAL:
raise KeyError(
f"No palette named '{name}'. Available: {', '.join(SEQUENTIAL)}."
)
return LinearSegmentedColormap.from_list(f"pelagos_{key}", SEQUENTIAL[key])
[docs]
def cmap_for_variable(variable, default=None):
"""Colormap for a dataset variable name (case-insensitive), or ``default``
when the variable has no mapping in VARIABLE_PALETTES."""
key = VARIABLE_PALETTES.get(str(variable).upper())
if key is None:
return default
return get_cmap(key)
