Image manipulation

As explained in previous chapters, an image in the digital domain, such as on a computer, is made up of a grid-like structure with each grid cell termed a pixel. These pixels store a value representing information about the image. For a simple grayscale image, these pixels store an integer with range [0, 255]. Changing these pixel values also changes the image. One of the basic image manipulation techniques is modifying pixel values.

Let's start by displaying what is inside an image at pixel level. For simplicity, we will do analysis on a grayscale image:

# read an image 
img = cv2.imread('gray_flower.png')

The earlier code reads a grayscale image from a file, in this case the image is in PNG format. We can also convert from one type of image color format to another. In this case, to convert a colored image to grayscale, OpenCV provides functions...