To create a digital image, we need to convert the continuous sensed data into digital form.
This process includes 2 processes:
- Sampling: Digitizing the co-ordinate value is called sampling.
- Quantization: Digitizing the amplitude value is called quantization.
To convert a continuous image f(x, y) into digital form, we have to sample the function in both co-ordinates and amplitude.
Difference between Image Sampling and Quantization:
| Sampling |
Quantization |
| Digitization of co-ordinate values. |
Digitization of amplitude values. |
| x-axis(time) - discretized. |
x-axis(time) - continuous. |
| y-axis(amplitude) - continuous. |
y-axis(amplitude) - discretized. |
| Sampling is done prior to the quantization process. |
Quantizatin is done after the sampling process. |
| It determines the spatial resolution of the digitized images. |
It determines the number of grey levels in the digitized images. |
| It reduces c.c. to a series of tent poles over a time. |
It reduces c.c. to a continuous series of stair steps. |
| A single amplitude value is selected from different values of the time interval to represent it. |
Values representing the time intervals are rounded off to create a defined set of possible amplitude values. |
