add a line to the README, and avoid creating string

README.md

@@ -11,8 +11,10 @@ Quickstart, based on the [PROJ docs](https://proj.org/development/quickstart.htm
 using Proj
 
 # Proj.jl implements the CoordinateTransformations.jl API.
-# A Proj.Transformation needs the source and target coordinate reference systems.
+# A Proj.Transformation needs the source and target coordinate reference systems (CRS),
+# or a single pipeline.
 trans = Proj.Transformation("EPSG:4326", "+proj=utm +zone=32 +datum=WGS84")
+# The CRS can be a string or the CRS type, which also interfaces with GeoFormatTypes.jl.
 
 # Once created, you can call this object to transform points.
 # The result will be a tuple of Float64s, of length 2, 3 or 4 depending on the input length.

src/crs.jl

@@ -127,8 +127,9 @@ function GFT.ProjJSON(crs::CRS; ctx::Ptr{PJ_CONTEXT} = C_NULL)
 end
 
 function GFT.EPSG(crs::CRS)
-    code = proj_get_id_code(crs)
-    return GFT.EPSG("EPSG:" * code)
+    str = proj_get_id_code(crs)
+    code = parse(Int, str)
+    return GFT.EPSG(code)
 end
 
 Base.convert(T::Type{<:GFT.CoordinateReferenceSystemFormat}, crs::CRS) = T(crs)