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/

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:]))

@jpdarela Thank you! Done.

@AkliDif Assuming you can find the XML file, you would have to parse it into an array and then do something like this

If all you have is an image of the colourmap, then unmap might be able to recover a matplotlib colourmap from it.