Explain the basic concepts of Sampling and Quantization

To create a digital image Convert the continuous sensed data into digital form. This involves two processes: sampling and quantization.
  Sampling: Digitizing the coordinate values.
  Quantization: Digitizing the amplitude values.

The basic idea behind sampling and quantization is illustrated in Fig. 2.5. Figure 2.5 (a) shows a continuous image, f (x, y), that we want to convert to digital form. An image may be continuous with respect to the x   and 

y-coordinates, and also in amplitude. To convert it to digital form, we have to sample the function in both coordinates and in amplitude. Digitizing the coordinate values is called sampling. Digitizing the amplitude values is called quantization.