Python Image Processing Cookbook

How to do it...

Execute the following steps to implement image compression using wavelets:

1. First, read the input image and convert it into grayscale:

im = mahotas.imread('images/cameraman.png', as_grey=True)im = im.astype(np.uint8)print(im.shape)# (256,256)f = np.mean(im==0)print("Fraction of zeros in original image: {}".format(f))# Fraction of zeros in original image: 0.0021514892578125

2. Try a baseline compression method using simple down-sampling (by saving every other pixel) and saving only the high-order bits:

im1 = im[::2,::2].copy()im1 = im1 / 8im1 = im1.astype(np.uint8)f1 = np.mean(im1==0)print("Fraction of zeros in original image (after division \        by 8): {}".format(f1))# Fraction of zeros in original image (after division by 8): ...