How to change the linewidth of hatch in matplotlib?

Question

Is there a way to increase the width of hatch in matplotlib?

For example, the following code by specifying linewidth only changes the width of the edge. I

Answer 1

If you use pdf and have sudo rights you can change it in backend_pdf.py. There is a line

self.output(0.1, Op.setlinewidth)

Usually it is located in /usr/lib/pymodules/python2.7/matplotlib/backends/backend_pdf.py .

Also someone wrote a hack to do this from your script (still need sudo rights to execute). Solution from here: http://micol.tistory.com/358

import os
import re
import matplotlib

def setHatchThickness(value):
libpath = matplotlib.__path__[0]
backend_pdf = libpath + "/backends/backend_pdf.py"
with open(backend_pdf, "r") as r:
    code = r.read()
    code = re.sub(r'self\.output\((\d+\.\d+|\d+)\,\ Op\.setlinewidth\)',
                   "self.output(%s, Op.setlinewidth)" % str(value), code)
    with open('/tmp/hatch.tmp', "w") as w:
        w.write(code)
    print backend_pdf
    os.system('sudo mv /tmp/hatch.tmp %s' % backend_pdf)


setHatchThickness(1.0)

Answer 2

There is a solution which is very hacky, but allows you to do what you want without changing matplotlib internal files: you can monkey patch the writeHatches of PdfFile like so:

# make sure you have the correct imports,
# they may differ depending on the matplotlib version
import matplotlib.backends.backend_pdf
from matplotlib.externals import six
from matplotlib.backends.backend_pdf import Name, Op
from matplotlib.transforms import Affine2D

def setCustomHatchWidth(customWidth):

     def _writeHatches(self):
        COPY CODE FROM matplotlib.__path__[0] + "/backends/backend_pdf.py" HERE
        change the line 
            self.output(0.1, Op.setlinewidth)
        to 
            self.output(customWidth, Op.setlinewidth)

    matplotlib.backends.backend_pdf.PdfFile.writeHatches = _writeHatches

You can then do

setCustomWidth(2)

before saving you figure as pdf.

Answer 3

I have a workaround that may help some. I use this when making my final plots for reports. The width of the hatch is affected by the dpi setting in

plt.savefig('pic',dpi=300)

The following figure is done at 80 DPI

Then again at 400 DPI

I fully understand that this may introduce other issues, but I figured it is worth the mention.

Answer 4

As of matplotlib version 2.0, you can directly change the linewidth parameter, as follows:

import matplotlib as mpl
mpl.rcParams['hatch.linewidth'] = 0.1  # previous pdf hatch linewidth
mpl.rcParams['hatch.linewidth'] = 1.0  # previous svg hatch linewidth

This seems a better workaround than what folks have above. You can check the matplotlib version by:

import matplotlib as mpl
print(mpl.__version__) # should be 2.x.y