Image Coding
Since a digital image has a finite number of gray levels, we may see it as being made up of a number of steps or plateaus, with the gray levels being the plateau heights.
Knowledge of the heights, locations and shapes of the plateaus is equivalent to knowledge of the image.
The left-most-looking rule for tracing a contour:
- Look at the element to the left relative to the direction of entry; if this has the same value move to it;
- else look at the element straight ahead ...
- else look right ...else look back …
Freeman's chain code may be used to encode the directions of movement in tracing the contour.