using 2d colormap for line plots

The package can be used to generate 2d colormaps to color lines in a line plot, as follows: (see also https://github.com/trygvrad/colorstamps/tree/main/examples/color_for_line_plots.ipynb)

Example:

import numpy as np
import matplotlib.pyplot as plt
import colorstamps

# intensities: array of shape (l,l,n)
# omega: array of shape (l,l)
# phi: array of shape (l,l)
# phase: array of shape (n)

# here l = 5, and n is 41

var_0 = np.array(omega)
var_1 = np.array(phi)
l = phi.shape[0]
rgb, stamp = colorstamps.apply_stamp(var_0, var_1, 'abyss', l = l,
           vmin_0 = np.min(var_0) - 0.5*(np.max(var_0)-np.min(var_0))/l,
           vmax_0 = np.max(var_0) + 0.5*(np.max(var_0)-np.min(var_0))/l,
           vmin_1 = np.min(var_1) - 0.5*(np.max(var_1)-np.min(var_1))/l,
           vmax_1 = np.max(var_1) + 0.5*(np.max(var_1)-np.min(var_1))/l,
         )


fig, ax = plt.subplots(dpi = 300)
for i, row in enumerate(intensities):
    for j, intensity in enumerate(row):
            ax.plot(phase, intensity/np.max(intensity), color = rgb[i,j])

ax.set_xticks(phase[::10])
ax.set_xticklabels(phase[::10]%360)
ax.set_ylabel('Amplitude')
ax.set_xlabel('Phase')
ax.set_xlim((0,360))
overlaid_ax = stamp.overlay_ax(ax, lower_left_corner = [0.15,0.25], width = 0.2)
overlaid_ax.set_xlabel(r'$\phi$')
overlaid_ax.set_ylabel(r'$\omega$')