composite.py

""" 
Test how to composite matrices with 'where' 
Test generator builds random incrementing matrices
The compositor takes output from this generator and performs the compositing.
Display an image map of the matrices
"""

import numpy as np
from matplotlib import pyplot as pl

def screen_generator(n, size):
    """ 
    Generates a matrix with 1's in randomly selected positions.
    At each iteration of the generator, the matrix is scalar
    multiplied by the current step sequence number. This results
    in a matrix with the current step number in random positions.
    """
    for i in range(n):
        yield np.random.binomial(1, .5, (size,size)) * (i+1)
        
def compositor(gen):
    """ 
    Produces a generator that overlays each screen 
    """
    composite = 0              # Keeps aggregation of composites
    for screen in gen: 
        # Take the values that are nonzero from screen and 
        # keep them in position. For all other values, take 
        # What is stored in composite.
        composite = np.where(screen > 0, screen, composite)
        yield composite

# Test and display
g = screen_generator(10, 20)
c = compositor(g)

pl.set_cmap('viridis')
for image in c:
    pl.imshow(next(c))