Matplotlib colourmaps for QGIS

README.md

mpl2qgis

See script below.

Make sure the Python file is executable. Then:

$ ./mpl2qgis.py viridis bone

This writes a file colourmaps.xml. Result:

<!DOCTYPE qgis_style>
<qgis_style version="0">
<symbols/>
<colorramps>
    <colorramp type="gradient" name="viridis">
    <prop k="color1" v="68,1,84,255"/>
    <prop k="color2" v="253,231,37,255"/>
    <prop k="stops" v="0.04;71,16,99,255:0.08;72,29,111,255:0.12;71,42,122,255:0.16;69,55,129,255:0.2;65,68,135,255:0.24;60,79,138
,255:0.28;55,90,140,255:0.32;50,100,142,255:0.36;46,111,142,255:0.4;42,120,142,255:0.44;38,130,142,255:0.48;34,139,141,255:0.52;31,1
49,139,255:0.56;31,159,136,255:0.6;34,168,132,255:0.64;44,177,126,255:0.68;59,187,117,255:0.72;78,195,107,255:0.76;99,203,95,255:0.8
;122,209,81,255:0.84;149,216,64,255:0.88;176,221,47,255:0.92;202,225,31,255:0.96;229,228,25,255"/>
    </colorramp>
    <colorramp type="gradient" name="bone">
    <prop k="color1" v="0,0,0,255"/>
    <prop k="color2" v="255,255,255,255"/>
    <prop k="stops" v="0.04;9,9,12,255:0.08;18,17,24,255:0.12;26,26,37,255:0.16;35,35,49,255:0.2;45,45,62,255:0.24;53,53,74,255:0.
28;62,62,86,255:0.32;71,71,99,255:0.36;80,80,112,255:0.4;89,92,121,255:0.44;98,104,130,255:0.48;107,116,139,255:0.52;116,129,148,255
:0.56;125,141,157,255:0.6;134,154,166,255:0.64;143,166,174,255:0.68;152,179,184,255:0.72;161,191,193,255:0.76;172,202,202,255:0.8;18
5,210,210,255:0.84;200,220,220,255:0.88;214,229,229,255:0.92;228,238,237,255:0.96;241,246,246,255"/>
    </colorramp>
</colorramps>
</qgis_style>

To install the color ramps, go to QGIS > Settings > Style Manager > Color ramp, hit the green + sign, and select the file.

Why

https://twitter.com/AndyDoggerBank/status/1085527532470968321

Inspiration

http://rocksandwater.net/blog/2016/07/qgis_perceptually_uniform_colorramps/

Update

Change the import in line 9 to:

from matplotlib import colormaps as mpc

Reason: avoid the following deprecation warning:

MatplotlibDeprecationWarning: The get_cmap function was deprecated in Matplotlib 3.7 and will be removed two minor releases later. Use ``matplotlib.colormaps[name]`` or ``matplotlib.colormaps.get_cmap(obj)`` instead.

Using python 3.11.4 and matplotlib 3.7.2 in conda

mpl2qgis.py

#!/usr/bin/env python
#-*- coding:utf-8 -*-
"""
Converts matplotlib colourmaps to QGIS colourmaps.
Matt Hall, 2019, released into public domain / CC-0.
"""
import sys

from matplotlib import colormaps as mpc

XML = """<!DOCTYPE qgis_style>
<qgis_style version="0">
  <symbols/>
  <colorramps>
{0}
  </colorramps>
</qgis_style>"""

CRAMP = """    <colorramp type="gradient" name="{name}">
      <prop k="color1" v="{color1}"/>
      <prop k="color2" v="{color2}"/>
      <prop k="stops" v="{stops}"/>
    </colorramp>"""


def get_rgba(name, value):
    """Get (R, G, B, A) for a value on a matplotlib colormap.
    """
    cmap = mpc.get_cmap(name)
    rgba = [str(int(round(255*v, 0))) for v in cmap(value)]
    return rgba    


def qgis_xml(name):
    params = {'name': name}
    params['color1'] = ','.join(get_rgba(name, 0.0))
    params['color2'] = ','.join(get_rgba(name, 1.0))
    stops = []
    for v in range(4, 100, 4):
        v /= 100
        s = f'{v};'
        s += ','.join(get_rgba(name, v))
        stops.append(s)
    params['stops'] = ':'.join(stops)
    return CRAMP.format(**params)


def mpl2qgis(names):
    cramps = '\n'.join(qgis_xml(name) for name in names)
    return XML.format(cramps)


if __name__ == '__main__':
    with open('colourmaps.xml', 'w') as f:
        f.write(mpl2qgis(sys.argv[1:]))