Hands-On Image Processing with Python

Up-sampling

As discussed briefly in Chapter 1, Getting Started with Image Processing, in order to increase the size of an image we need to up-sample the image. The challenge is that the new larger images will have some pixels that have no corresponding pixel in the original smaller image, and we need to guess those unknown pixel values. We can guess the value of an unknown pixel using the following:

• An aggregate, for example, the mean value of its nearest known one or more pixel-neighbors values
• An interpolated value using pixel-neighbors with bi-linear or cubic interpolation 

Nearest neighbor-based up-sampling may result in a poor quality output image. Let's code to verify this: 

im = Image.open("../images/clock.jpg") # the original small ...