[gdal-dev] Open source API to convert raster to polygons?

[Chris Barker]

Ricardo Scachetti Pereira wrote:
>    What I really need is some API or software library (preferably in C 
> or C++) that I could use to convert ESRI Arc/Info Grids (the binary 
> kind) to a Shapefile of polygons.

Well, no, that doesn't answer the question at all. Polygons and Raster 
data are completely different concepts. Raster data is one or more 
values at a bunch of points on a grid -- what do you want your polygons 
to represent? I can think of two fairly obvious possibilities:

1) There are polygons visually represented in the raster -- maybe is was 
actually created by rendering polygons in the first place (like a map 
with boundaries or something). In this case, you're looking for line 
tracing or edge-detection tools.

2) Your raster represent some continuous field, like elevation n a DEM . 
In this case, you might want to contour the data, and get the contours 
as polygons. If this is the case, look for contouring code.

There are probably an infinite number of other ways one might want to 
extract polygons from raster data -- we need to know what you're trying 
to do to help any more.

-Chris


-- 
Christopher Barker, Ph.D.
Oceanographer

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