Vectorisation

Stages of Vectorisation

WinTopo employs a two stage vectorisation process:

Thinning of the raster image to single pixel width lines.
Extraction of vectors from the pixel lines.

Vector Extraction

NOTE: WinTopo Freeware and WinTopo Pro use different vectorisation algorithms, and so produce slightly different results. The results from WinTopo Freeware are very competent and will be suitable for many users. WinTopo Pro benefits from recent research and development, and so produces a more optimised result.

Once a raster has been thinned down to lines of single width pixels, the vectorise button can be used to extract real vectors. This also occurs as the last stage of the 1 Touch Vectorisation option.

During vectorisation a progress meter window shows how quickly the vectorisation is performing, and the number of pixels processed.

When complete, the vectors will be displayed over the top of the raster image. The vectors will be drawn in green (and blue for arcs) unless you have set the Show Line Colour option under the View menu, in which case the vectors will be shown in their actual colours.
Note: when the Show Line Colour option is used the vectors will be the same colour as the raster image, so will not show up well (if at all) against the raster. Therefore the View->Show Raster Image option is usually turned off, so that the raster is not displayed.

The quality or accuracy and number of vectors extracted can be varied by selecting options on the Vector Extraction Options window

Here are some differences between the results produced by the Freeware and Professional versions:

The Professional version extracts coloured polylines, whereas the Freeware version produces only black polylines.
The Professional version examines lines intersections and junctions to determine which polylines should continue through the junction and which should stop at it. The Freeware version stops all polylines at intersections and junctions.
The Professional version produces far less vectors and polylines than the Freeware version. Usually only ½ as many lines are produced by the Professional version, resulting in much smaller CAD/GIS output drawings.