For image quantization, is it necessary to sample image?

1. Why is sampling done before quantization?
2. What is necessity of quantization in image processing?
3. Why is sampling and quantization required to convert?

Why is sampling done before quantization?

The sampling rate determines the spatial resolution of the digitized image, while the quantization level determines the number of grey levels in the digitized image. A magnitude of the sampled image is expressed as a digital value in image processing.

What is necessity of quantization in image processing?

Color quantization reduces the number of colors used in an image; this is important for displaying images on devices that support a limited number of colors and for efficiently compressing certain kinds of images.

Why is sampling and quantization required to convert?

We use sampling and quantization to change the continuous analog image into quantized integral values that will represent each pixel and ultimately form the digital image.