Getting data out of a data frame heatplot (not x nor y columns)

Question

I want to get a profile of intensity out of a dataframe heat map but the data is not only in a row or column, for example:

import numpy as np 
from pandas import DataFrame
import matplotlib.pyplot as plt

index = ['1', '2', '3', '4', '5']
columns = ['A', 'B', 'C', 'D']
df = DataFrame(abs(np.random.randn(5, 4)), index=index, columns=columns)

plt.pcolor(df)
plt.yticks(np.arange(0.5, len(df.index), 1), df.index)
plt.xticks(np.arange(0.5, len(df.columns), 1), df.columns)
plt.show()

Is there a way to plot a profile from A2 to D4 (for example), maybe even doing some interpolation to get bit more smooth data.

Any ideas?