Mumbai University > Electronics > Sem 7 > Digital image processing

Marks: 5M

Year: May 2013

There are three basic types of discontinuities in the grey level i.e points, lines and edges. The easiest way is to use spatial masks which have properties to detect these discontinuities.

Point Detection: Points, lines and edges are all high frequency components and hence need masks which are basically high pass. Hence the masks that present the point, line and edge detection have the properties of a high mask mainly, the sum of the coefficients of the mask has to be equal to 0 in all the cases.

Line Detection: In an image, lines can be in any direction and the detecting lines need different masks.

All the masks have sum equal to zero and hence all of them are high pass masks. The first mask respond strongly to lines that are oriented horizontally. The second mask respond at the angle +450, the third mask respond strongly to the vertical lines and the last mask strongly to the lines at an angle of -450.

Edge Detection: More than isolated points and lines, it is the detection of the edges that form an important part of image segmentation. An edge can be defined as a set of connected pixels that form a boundary between two disjoint regions.

Here the set of pixels that separate the black region from the grey region is called an edge. The line profile of such an edge is shown along with the edge.