Why Edge Detection Is A Non-trivial Task
To illustrate why edge detection is not a trivial task, consider the problem of detecting edges in the following one-dimensional signal. Here, we may intuitively say that there should be an edge between the 4th and 5th pixels.
| 5 | 7 | 6 | 4 | 152 | 148 | 149 |
If the intensity difference were smaller between the 4th and the 5th pixels and if the intensity differences between the adjacent neighboring pixels were higher, it would not be as easy to say that there should be an edge in the corresponding region. Moreover, one could argue that this case is one in which there are several edges.
| 5 | 7 | 6 | 41 | 113 | 148 | 149 |
Hence, to firmly state a specific threshold on how large the intensity change between two neighbouring pixels must be for us to say that there should be an edge between these pixels is not always simple. Indeed, this is one of the reasons why edge detection may be a non-trivial problem unless the objects in the scene are particularly simple and the illumination conditions can be well controlled (see for example, the edges extracted from the image with the girl above).
Read more about this topic: Edge Detection
Famous quotes containing the words edge and/or task:
“The stroke of the whip maketh marks in the flesh: but the stroke of the tongue breaketh the bones. Many have fallen by the edge of the sword: but not so many as have fallen by the tongue.”
—Ecclesiasticus Apocrypha. Ecclesiasticus, 28:17-8.
“Three million of such stones would be needed before the work was done. Three million stones of an average weight of 5,000 pounds, every stone cut precisely to fit into its destined place in the great pyramid. From the quarries they pulled the stones across the desert to the banks of the Nile. Never in the history of the world had so great a task been performed. Their faith gave them strength, and their joy gave them song.”
—William Faulkner (1897–1962)