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<html><head><title>.SHP File API</title></head><body><h1>.SHP File API</h1>The .SHP API uses a SHPHandle to represent an open .shp/.shx file pair.The contents of the SHPHandle are visible (see shapefile.h) but shouldbe ignored by the application. It is intended that all information beaccessed by the API functions. <p><!--------------------------------------------------------------------------><h2>Shape Types</h2>Shapes have types associated with them. The following is a list of thedifferent shapetypes supported by Shapefiles. At this time all shapes ina Shapefile must be of the same type (with the exception of NULL shapes). <p><pre> #define SHPT_NULL 0 2D Shape Types (pre ArcView 3.x): #define SHPT_POINT 1 Points #define SHPT_ARC 3 Arcs (Polylines, possible in parts) #define SHPT_POLYGON 5 Polygons (possible in parts) #define SHPT_MULTIPOINT 8 MultiPoint (related points) 3D Shape Types (may include "measure" values for vertices): #define SHPT_POINTZ 11 #define SHPT_ARCZ 13 #define SHPT_POLYGONZ 15 #define SHPT_MULTIPOINTZ 18 2D + Measure Types: #define SHPT_POINTM 21 #define SHPT_ARCM 23 #define SHPT_POLYGONM 25 #define SHPT_MULTIPOINTM 28 Complex (TIN-like) with Z, and Measure: #define SHPT_MULTIPATCH 31</pre><!--------------------------------------------------------------------------><h2>SHPObject</h2>An individual shape is represented by the SHPObject structure. SHPObject'screated with SHPCreateObject(), SHPCreateSimpleObject(), or SHPReadObject()should be disposed of with SHPDestroyObject().<p><pre> typedef struct { int nSHPType; Shape Type (SHPT_* - see list above) int nShapeId; Shape Number (-1 is unknown/unassigned) int nParts; # of Parts (0 implies single part with no info) int *panPartStart; Start Vertex of part int *panPartType; Part Type (SHPP_RING if not SHPT_MULTIPATCH) int nVertices; Vertex list double *padfX; double *padfY; double *padfZ; (all zero if not provided) double *padfM; (all zero if not provided) double dfXMin; Bounds in X, Y, Z and M dimensions double dfYMin; double dfZMin; double dfMMin; double dfXMax; double dfYMax; double dfZMax; double dfMMax; } SHPObject;</pre><!--------------------------------------------------------------------------><h2>SHPOpen()</h2><pre>SHPHandle SHPOpen( const char * pszShapeFile, const char * pszAccess ); pszShapeFile: The name of the layer to access. This can be the name of either the .shp or the .shx file or can just be the path plus the basename of the pair. pszAccess: The fopen() style access string. At this time only "rb" (read-only binary) and "rb+" (read/write binary) should be used.</pre> The SHPOpen() function should be used to establish access to the two files for accessing vertices (.shp and .shx). Note that both files have to be in the indicated directory, and must have the expected extensions in lower case. The returned SHPHandle is passed to other access functions, and SHPClose() should be invoked to recover resources, and flush changes to disk when complete.<p><!--------------------------------------------------------------------------><h2>SHPGetInfo()</h2><pre>void SHPGetInfo( SHPHandle hSHP, int * pnEntities, int * pnShapeType, double * padfMinBound, double * padfMaxBound ); hSHP: The handle previously returned by SHPOpen() or SHPCreate(). pnEntities: A pointer to an integer into which the number of entities/structures should be placed. May be NULL. pnShapetype: A pointer to an integer into which the shapetype of this file should be placed. Shapefiles may contain either SHPT_POINT, SHPT_ARC, SHPT_POLYGON or SHPT_MULTIPOINT entities. This may be NULL. padfMinBound: The X, Y, Z and M minimum values will be placed into this four entry array. This may be NULL. padfMaxBound: The X, Y, Z and M maximum values will be placed into this four entry array. This may be NULL.</pre> The SHPGetInfo() function retrieves various information about shapefile as a whole. The bounds are read from the file header, and may be inaccurate if the file was improperly generated. <p> <!--------------------------------------------------------------------------><h2>SHPReadObject()</h2><pre>SHPObject *SHPReadObject( SHPHandle hSHP, int iShape ); hSHP: The handle previously returned by SHPOpen() or SHPCreate(). iShape: The entity number of the shape to read. Entity numbers are between 0 and nEntities-1 (as returned by SHPGetInfo()).</pre> The SHPReadObject() call is used to read a single structure, or entity from the shapefile. See the definition of the SHPObject structure for detailed information on fields of a SHPObject. SHPObject's returned from SHPReadObject() should be deallocated with SHPDestroyShape(). SHPReadObject() will return NULL if an illegal iShape value is requested.<p> Note that the bounds placed into the SHPObject are those read from the file, and may not be correct. For points the bounds are generated from the single point since bounds aren't normally provided for point types.<p> Generally the shapes returned will be of the type of the file as a whole. However, any file may also contain type SHPT_NULL shapes which will have no geometry. Generally speaking applications should skip rather than preserve them, as they usually represented interactively deleted shapes.<p><!--------------------------------------------------------------------------><h2>SHPClose()</h2><pre>void SHPClose( SHPHandle hSHP ); hSHP: The handle previously returned by SHPOpen() or SHPCreate().</pre> The SHPClose() function will close the .shp and .shx files, and flush all outstanding header information to the files. It will also recover resources associated with the handle. After this call the hSHP handle cannot be used again.<p><!--------------------------------------------------------------------------><h2>SHPCreate()</h2><pre>SHPHandle SHPCreate( const char * pszShapeFile, int nShapeType ); pszShapeFile: The name of the layer to access. This can be the name of either the .shp or the .shx file or can just be the path plus the basename of the pair. nShapeType: The type of shapes to be stored in the newly created file. It may be either SHPT_POINT, SHPT_ARC, SHPT_POLYGON or SHPT_MULTIPOINT.</pre> The SHPCreate() function will create a new .shp and .shx file of the desired type.<p><!--------------------------------------------------------------------------><h2>SHPCreateSimpleObject()</h2><pre>SHPObject * SHPCreateSimpleObject( int nSHPType, int nVertices, double *padfX, double * padfY, double *padfZ, ); nSHPType: The SHPT_ type of the object to be created, such as SHPT_POINT, or SHPT_POLYGON. nVertices: The number of vertices being passed in padfX, padfY, and padfZ. padfX: An array of nVertices X coordinates of the vertices for this object. padfY: An array of nVertices Y coordinates of the vertices for this object. padfZ: An array of nVertices Z coordinates of the vertices for this object. This may be NULL in which case they are all assumed to be zero.</pre> The SHPCreateSimpleObject() allows for the convenient creation of simple objects. This is normally used so that the SHPObject can be passed to SHPWriteObject() to write it to the file. The simple object creation API assumes an M (measure) value of zero for each vertex. For complex objects (such as polygons) it is assumed that there is only one part, and that it is of the default type (SHPP_RING). <p> Use the SHPCreateObject() function for more sophisticated objects. The SHPDestroyObject() function should be used to free resources associated with an object allocated with SHPCreateSimpleObject(). <p> This function computes a bounding box for the SHPObject from the given vertices.<p><!--------------------------------------------------------------------------><h2>SHPCreateObject()</h2><pre>SHPObject * SHPCreateObject( int nSHPType, int iShape, int nParts, int * panPartStart, int * panPartType, int nVertices, double *padfX, double * padfY, double *padfZ, double *padfM ); nSHPType: The SHPT_ type of the object to be created, such as SHPT_POINT, or SHPT_POLYGON. iShape: The shapeid to be recorded with this shape. nParts: The number of parts for this object. If this is zero for ARC, or POLYGON type objects, a single zero valued part will be created internally. panPartStart: The list of zero based start vertices for the rings (parts) in this object. The first should always be zero. This may be NULL if nParts is 0. panPartType: The type of each of the parts. This is only meaningful for MULTIPATCH files. For all other cases this may be NULL, and will be assumed to be SHPP_RING. nVertices: The number of vertices being passed in padfX, padfY, and padfZ. padfX: An array of nVertices X coordinates of the vertices for this object. padfY: An array of nVertices Y coordinates of the vertices for this object. padfZ: An array of nVertices Z coordinates of the vertices for this object. This may be NULL in which case they are all assumed to be zero. padfM: An array of nVertices M (measure values) of the vertices for this object. This may be NULL in which case they are all assumed to be zero.</pre> The SHPCreateSimpleObject() allows for the creation of objects (shapes). This is normally used so that the SHPObject can be passed to SHPWriteObject() to write it to the file. <p> The SHPDestroyObject() function should be used to free resources associated with an object allocated with SHPCreateObject(). <p> This function computes a bounding box for the SHPObject from the given vertices.<p><!--------------------------------------------------------------------------><h2>SHPComputeExtents()</h2><pre>void SHPComputeExtents( SHPObject * psObject ); psObject: An existing shape object to be updated in place.</pre> This function will recompute the extents of this shape, replacing the existing values of the dfXMin, dfYMin, dfZMin, dfMMin, dfXMax, dfYMax, dfZMax, and dfMMax values based on the current set of vertices for the shape. This function is automatically called by SHPCreateObject() but if the vertices of an existing object are altered it should be called again to fix up the extents.<p><!--------------------------------------------------------------------------><h2>SHPWriteObject()</h2><pre>int SHPWriteObject( SHPHandle hSHP, int iShape, SHPObject *psObject ); hSHP: The handle previously returned by SHPOpen("r+") or SHPCreate(). iShape: The entity number of the shape to write. A value of -1 should be used for new shapes. psObject: The shape to write to the file. This should have been created with SHPCreateObject(), or SHPCreateSimpleObject().</pre> The SHPWriteObject() call is used to write a single structure, or entity to the shapefile. See the definition of the SHPObject structure for detailed information on fields of a SHPObject. The return value is the entity number of the written shape. <p><!--------------------------------------------------------------------------><h2>SHPDestroyObject()</h2><pre>void SHPDestroyObject( SHPObject *psObject ); psObject: The object to deallocate.</pre> This function should be used to deallocate the resources associated with a SHPObject when it is no longer needed, including those created with SHPCreateSimpleObject(), SHPCreateObject() and returned from SHPReadObject(). <p></body></html>⌨️ 快捷键说明
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