How to Transform Raster into Vector

The transformation from raster representation to vector representation is a more complex process than the other way around (that is vector to raster), because, besides extracting the objects contour, it is also required to create the spatial relations among them, such as neighborhood relationship, and pertinence between polygons, and connectivity between arcs.

The transformation process raster-vector described here is adequate only for data from models where the objects present has an area, that is polygons.

Starting from the original image, the algorithm generates a binary image that has only the boundaries among the objects present, as shown in the example below:


convert9.gif - 3275 Bytes


  1. The boundaries are constructed using the pixels: if the original image has (n x n) format, where n is the number of lines and also the number of columns, the binary image will have (2n + 1) x (2n + 1) format.
  2. When transforming the image into the binary format, the nodes are also detected.
  3. Next, the object contours are extracted (vectorized) from the binary image and smoothed to attenuate the "step effect", which is a raster representation characteristic.
  4. Finally, the polygons are built and the spatial relations (neighborhood, polygons pertinence and arc connectivity).

Before using this function, it is required to observe the thematic image aspect. The aspect is directly related to its homogeneity. The more homogeneous the image, the larger the probability of a successful vectorization.



Transforming from raster to vector:

  • activate the Database ( ) and the desired Project ( );
  • select, using the "Control Panel" the IL from the Thematic category of raster representation (image) that will have its classes represented in the vector format;
  • click on Thematic - Raster -> Vector... in the main menu;
  • in Current Infolayer: it is informed whatever was selected in the "Control Panel";
  • click on Yes in the Arc Smoothing button so the smoothing process will be executed, or click on No if the raster borders should be considered in the vector format;
  • select the Conversion Type (Total or Only Arcs). If Total is selected a topology will be created (line adjustment and polygonalization), and if Only Arcs is selected only the lines file will be created;
  • click on Apply to execute the transformation.


NOTE: Check, using the "Control Panel" , that the information layer will have a vector representation (points, lines and polygon classes).



See about vector representations and raster in the SPRING

See also:
Vector-Raster Transformation