Images with Python

image_example.py

from matplotlib import pyplot as plt # the standard python plotting library
# installation instructions here: https://github.com/matplotlib/matplotlib
import numpy as np # math library for data-handling

# DEMO on random matrix to show how filtering based on pixel intensity works. How to make an image. 
n = 20
I = np.random.random((n, n))
I[I>0.5] = 1 # highpass filter in two lines of code.
I[I<0.5] = 0 

colormap = plt.cm.gray # any of these: https://matplotlib.org/users/colormaps.html
plt.imshow(I, cmap=colormap) # plot in Black and White
# this line below tells matplotlib "I'm done constructing my image (titles, labels, etc.), now show me it." sometimes unecessary. depends on how you're interacting with python
plt.show() 

# HOW TO LOAD A FILE
filename = 'myfile.png'
I = plt.imread(filename) # this is how to load an image
plt.imshow(I) 
plt.title('Original Image'); plt.ylabel('px'); plt.xlabel('px');
plt.show()



# CONVERT image to grayscale
def rgb2gray(rgb):
    r, g, b = rgb[:,:,0], rgb[:,:,1], rgb[:,:,2]
    gray = 0.2989 * r + 0.5870 * g + 0.1140 * b
    return gray

G = rgb2gray(I)
# OPTIONAL - CROPPING
# G = G[375:1175,330:950] # overwrite image with cropped version
plt.imshow(G)
plt.show()