Changes between Version 1 and Version 2 of LayerAlgebra

Timestamp:

Aug 6, 2012, 6:35:37 AM (12 years ago)

Author:

Ari Jolma

Comment:

--

LayerAlgebra

@@ -1 +1 @@
 = GDAL Layer Algebra =
 
-This page describes in detail the GDAL layer algebra.
+This page describes the GDAL layer algebra in detail and gives examples.
 
 == Common ideas ==
 
+The GDAL layer algebra is implemented as methods in the OGRLayer class. The C API is similar to the methods except that the object itself is the first argument and that the layer pointers are validated. In the Swig bindings these are again methods in Layer class.
+
+Each method works on the object itself (the "input" layer) and a second operand (the "method" layer) and produces a result layer. The result layer needs to exist when calling any of these methods (this may not be the case in bindings languages).
+
+The schema of the result layer can be user-defined (the layer definition of the result layer has one or more fields) or it can be created by the method. If created, it will be either the schema of the input layer or the combined schema of input and method layers, depending on the method.
+
+Each method may accept additional options.
+
+A progress callback function can be used with each method.
+
+The methods return an error code and set an error context if an error occurs or the execution is interrupted. This may have been converted into an exception in bindings languages.
+
 == Intersection ==
+
+An intersection is a set of features, which represent the common areas of two layers.
+
+[[Image(Intersection.jpg)]]
 
 == Union ==
 
-== SymDifference ==
+== !SymDifference ==
 
 == Identity ==