In most cases, major variations in intensity in an image correspond to edges of objects. You can often extract objects in an image by detecting these variations through a process called segmentation. In GIMP, you can do this using the edge detection tools.
Technically, the edges in an image are any areas where the intensity presents a strong local variation. Edge detection is a fundamental part of extracting information from an image during preprocessing. Often, the discovered edges are then fed to a shape recognition system. Shape recognition has applications in robotics, medical image analysis, video surveillance, and other fields.
Figure 7-64. After a strong Gaussian blur
Figure 7-65. The Edge-Detect ...