The Edge Detect - Advanced... function is available on the Image menu, or by clicking the toolbar button. (This option is not available on the Freeware version)
This option finds the edges of solid features in the image. It has the effect of hollowing out the solid shapes, leaving just their outlines, whilst leaving the linear features unchanged.
Use the slider to select the size of object to hollow out. Only objects this size or larger will be affected. When you click the Process button WinTopo will search the image for solid features and leave only their edges, filling their centres with light coloured pixels.
The Advanced Edge Detection function is useful for when you want to vectorise the outlines of solid shapes, rather than get vectors representing the centreline of the solids.
The Advanced Edge Detection is also very useful for decreasing the thinning time of large rasters. An image will often have one or two large solid features (for instance a logo in a drawing title box). A large solid feature can take a lot of thinning to find its centreline, and in a large raster the processing time can become significant. In such cases, first doing Advanced Edge Detection to hollow out the solids can decrease the processing time hugely.