DSP is used extensively in image processing. For example as an in class project, lets remove the dithering patterns of dots in this image of Donald Duck.
These dots occur in the printing process used in newspapers in the past as a way to shade the picture without fine pixel or color control. The process was developed in the early nineteenth century by Ben Day, and is called the [Ben Day process].(https://en.wikipedia.org/wiki/Ben_Day_process)
import numpy as np
import matplotlib.pyplot as plt
import matplotlib
im = plt.imread("Donald_Duck.png")
im.shape
print(im.shape)
def plti(im, h=8, **kwargs):
"""
Helper function to plot an image.
"""
y = im.shape[0]
x = im.shape[1]
w = (y/x) * h
plt.figure(figsize=(w,h))
plt.imshow(im, interpolation="none", **kwargs)
plt.axis('off')
plt.show()
plti(im)
im1 = im[10:im.shape[0]-10, 10:im.shape[1]-10]
def rgb2gray(rgb):
return np.dot(rgb[...,:3], [0.2989, 0.5870, 0.1140])
gray_im = rgb2gray(im1)
plt.gray() # Means all further plots will be gray scale.
plti(gray_im)
Hint: See this web page if you have no ideas, but first please think about it and look at the image closely to see if you can figure it out yourself.