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cl-ewkb

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资源说明：Common Lisp PostGIS EWKB data model and encoder/decoder

cl-ewkb is a geospatial library, based on cl-wkb, that implements the OGC Well-Known Binary geographic geometry data model with PostGIS 3d, 4d extensions, and provides WKB and EWKB encoding and decoding functionality. cl-wkb author is J.P. Larocue.
Library also provide module cl-wkb, which has CLOS-based API like http://enroutesystems.com/software/cl-wkb/ with PostGIS extensions.

Depends on:
 ieee-floats
 flexi-streams

PostGIS extension WKB is described in postgis-1.5/doc/ZMSgeoms.txt
All extensions are supported: 3dz, 3dm, 4d, embedded SRID.

Exported structs

point-primitive x y
pointz-primitive x y z
pointm-primitive x y m
pointzm-primitive x y z m
point-primtive structs contain coordinates (2d, 3d, 4d)


linear-ring points-primitive
linear-ring struct contains array of point-primitive

geometry type srid
geometry parent struct for other types and also contains "GEOMETRYCOLLECTION"

point type srid point-primitive
line-string type srid points-primitive
polygon type srid linear-rings
multi-point type srid points
multi-line-string type srid line-strings
multi-polygon type srid polygons
geometry-collection type srid geometries

Exported functions

(decode octets)
Decode from wkb sequence
(decode-from stream)
Decode from wkb stream

Functions for encoding:

(encode object endianness)
Encode object to vector

(encode-to object stream endianness)
Encode object to stream with endianness

Example:

Getting data from postgresql and decode it:

(decode (caar (postmodern:query (:select (:ST_AsEWKB "SRID=4326;LINESTRING(0 0 1 2, 1 1 2 3, 2 2 3 4)")))))

Result:

#(CL-EWKB::GISGEOMETRY 3758096386 4326
  #(CL-EWKB::LINEAR-RING
    #(#(CL-EWKB::POINT-PRIMITIVE 0.0d0 0.0d0 CL-EWKB::POINTZ-PRIMITIVE 1.0d0
        CL-EWKB::POINTZM-PRIMITIVE 2.0d0)
      #(CL-EWKB::POINT-PRIMITIVE 1.0d0 1.0d0 CL-EWKB::POINTZ-PRIMITIVE 2.0d0
        CL-EWKB::POINTZM-PRIMITIVE 3.0d0)
      #(CL-EWKB::POINT-PRIMITIVE 2.0d0 2.0d0 CL-EWKB::POINTZ-PRIMITIVE 3.0d0
        CL-EWKB::POINTZM-PRIMITIVE 4.0d0)))
  CL-EWKB::LINESTRING)


Drawing data with opengl (using cl-opengl):

Draw pointXX-primitive

(defun draw-point-primitive (point)
    (cond
        ((point-primitive-p point)
            (gl:vertex
                (point-primitive-x point)
                (point-primitive-y point)))
        ((pointz-primitive-p point)
            (gl:vertex
                (point-primitive-x point)
                (point-primitive-y point)
                (pointz-primitive-z point)))
        ((pointm-primitive-p point)
            (gl:vertex
                (point-primitive-x point)
                (point-primitive-y point)
                0.0
                (pointm-primitive-m point)))
        ((pointzm-primitive-p point)
            (gl:vertex
                (point-primitive-x point)
                (point-primitive-y point)
                (pointz-primitive-z point)
                (pointzm-primitive-m point)))))

Drawing objects

(defun draw-point (point)
    (gl:with-primitives :points
        (draw-point-primitive (point-primitive point))))

(defun draw-points (line-string)
    (gl:with-primitives :line-strip
        (map 'nil (lambda (point) (draw-point-primitive point))
             (line-string-points-primitive line-string))))


General drawing function

(defun draw-gisobject (object)
    (cond
        ((point-p object) (draw-point object))
        ((line-string-p object) (draw-points object))))

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