import numpy as np
import matplotlib.pyplot as plt
from mpl_toolkits.axes_grid1.axes_divider import HBoxDivider
import mpl_toolkits.axes_grid1.axes_size as Size

def make_heights_equal(fig, rect, ax1, ax2, pad):
    # pad in inches
    
    h1, v1 = Size.AxesX(ax1), Size.AxesY(ax1)
    h2, v2 = Size.AxesX(ax2), Size.AxesY(ax2)

    pad_v = Size.Scaled(1)
    pad_h = Size.Fixed(pad)

    my_divider = HBoxDivider(fig, rect,
                             horizontal=[h1, pad_h, h2],
                             vertical=[v1, pad_v, v2])


    ax1.set_axes_locator(my_divider.new_locator(0))
    ax2.set_axes_locator(my_divider.new_locator(2))

    
if __name__ == "__main__":

    fig1 = plt.figure()

    arr1 = np.arange(20).reshape((4,5))
    arr2 = np.arange(20).reshape((5,4))

    ax1 = plt.subplot(121)
    ax2 = plt.subplot(122)

    ax1.imshow(arr1, interpolation="nearest")
    ax2.imshow(arr2, interpolation="nearest")

    rect = 111 # subplot param for combined axes
    make_heights_equal(fig1, rect, ax1, ax2, pad=0.5) # pad in inches
    
    for ax in [ax1, ax2]:
        ax.locator_params(nbins=4)

    # annotate
    ax3 = plt.axes([0.5, 0.5, 0.001, 0.001], frameon=False)
    ax3.xaxis.set_visible(False)
    ax3.yaxis.set_visible(False)
    ax3.annotate("Location of two axes are adjusted\n so that they have equal heights\n while maintaining their aspect ratios", (0.5, 0.5),
                 xycoords="axes fraction", va="center", ha="center",
                 bbox=dict(boxstyle="round, pad=1", fc="w"))

    plt.show()