[postgis-users] AsSvg

Darren Houston dhouston at beyondcompliance.ca
Wed Sep 8 08:47:31 PDT 2004


Hello all,

I use SVG and PostGIS in my web mapping applications. This e-mail is my 
advocate for including a function such as AsSvg into PostGIS, even for the 
purpose of expanding SVG usage on the web.

Thank you,

Darren H.

On September 8, 2004 08:10 am, Randy George wrote:
> Hi,
>
> 	I also would be glad to see assvg a native part of PostGIS. I
> currently have to translate results from wkt to/from svg and would welcome
> a more efficient approach.
>
> Thanks
> Randy
>
> -----Original Message-----
> From: postgis-users-bounces at postgis.refractions.net
> [mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of TECHER
> Jean David
> Sent: Wednesday, September 08, 2004 6:20 AM
> To: PostGIS Users Discussion
> Subject: RE: [postgis-users] AsSvg
>
> Hi Klaus
>
> Happy to see you... :-)
>
> I think it could be a great new if assvg was a native part of PostGIS
>
> TECHER JEAN DAVID
> - Responsable Informatique 01MAP -
> e-mail:davidtecher at yahoo.fr
> Tel: 06 85 37 36 75
> Site PostGIS: http://techer.pascal.free.fr/postgis/index.htm
>
> > -----Message d'origine-----
> > De : postgis-users-bounces at postgis.refractions.net
> > [mailto:postgis-users-bounces at postgis.refractions.net]De la part de
> > Olivier Courtin
> > Envoye : mercredi 8 septembre 2004 13:57
> > A : postgis-users at postgis.refractions.net
> > Cc : klaus at svg.cc
> > Objet : [postgis-users] AsSvg
> >
> >
> > Hi,
> >
> > I currently use PostGIS with AsSvg for several month (mostly web carto
> > usage).
> > Current AsSvg projet from klaus Foerster is available here :
> > <http://svg.cc/pg/assvg/>
> >
> > And i find a bit pity following things :
> > 1) AsSvg is not a native part of PostGIS (even if SVG output is in
> > PostGIS TODO)
> > 2) AsSvg output use double for decimal part (useless for most web carto
> > application)
> >
> >
> > For the second point, i've decided to add a new optional parameter in
> > AsSvg prototype to handle decimal precision (now default is 0 decimal).
> > I've also correct some very little things, like to avoid gcc to warn on
> > compiletime and so on...
> >
> > For the first point nevertheless, i don't know why AsSvg never add been
> > included directly in PostGIS source... Is there a real reason ?
> > I've found nothing on this ml archive...
> > It will be IMHO a great thing... :)
> >
> >
> > (Following code seems to work fine with PostGIS 0.8.1 or 0.8.2, not
> > tested with current CVS)
> >
> >
> >
> > =============== assvg.c.in ========================================
> >
> >
> >
> >
> > /**
> >  * SVG features
> >  */
> >
> > PG_FUNCTION_INFO_V1(assvg_geometry);
> > Datum assvg_geometry(PG_FUNCTION_ARGS)
> > {
> > 	GEOMETRY 	*geom1 = (GEOMETRY *)
> > 				PG_DETOAST_DATUM(PG_GETARG_DATUM(0));
> > 	char	   	*wkt;
> > 	char	   	*result;
> > 	int	   	len;
> > 	int32           svgrel;
> > 	int32		precision;
> >
> >
> > 	// check for relative path notation
> > 	if ( ! PG_ARGISNULL(1) )
> > 		svgrel = PG_GETARG_INT32(1);
> > 	else
> > 		svgrel = 0;
> >
> > 	if ( ! PG_ARGISNULL(2) )
> > 		precision = PG_GETARG_INT32(2);
> > 	else
> > 		precision = 0;
> >
> > 	wkt = geometry_to_svg(geom1, svgrel, precision);
> >
> > 	len = strlen(wkt) + 5;
> >
> > 	result= palloc(len);
> > 	*((int *) result) = len;
> >
> > 	memcpy(result +4, wkt, len-4);
> >
> > 	pfree(wkt);
> >
> > 	PG_RETURN_CSTRING(result);
> > }
> >
> >
> > //takes a GEOMETRY and returns a SVG representation
> > char *geometry_to_svg(GEOMETRY  *geometry, int svgrel, int precision)
> > {
> > 	char		*result;
> > 	int		t,u;
> > 	int32		*offsets;
> > 	char		*obj;
> > 	POINT3D	*pts;
> > 	POLYGON3D	*polygon;
> > 	LINE3D	*line;
> > 	POINT3D	*point;
> >
> > 	int		pt_off,size;
> > 	bool		first_sub_obj = TRUE;
> > 	int		mem_size,npts;
> >
> > 	size = 30;	//just enough to put in object type
> > 	//try to limit number of repalloc()s
> > 	result = (char *) palloc(30); mem_size= 30;
> >
> > 	// TODO BBox, from where is it called?...
> > 	if (geometry->type == BBOXONLYTYPE)
> > 	{
> > 		if (svgrel == 1)
> > 		{
> > 			// 5 double digits+ "Mhvhz"+ spaces +null
> > 			mem_size = MAX_DIGS_DOUBLE*5+5+6+1;
> > 			pfree(result);
> > 			result = (char *) palloc(mem_size);
> >
> > 			sprintf(result, "M %.*f %.*f h%.*f v%.*f h%.*f z",
> > 				precision,
> > 				geometry->bvol.LLB.x,
> > 				precision,
> > 				geometry->bvol.URT.y*-1,
> > 				precision,
> > 				(geometry->bvol.URT.x
> > 				 - geometry->bvol.LLB.x),
> > 				precision,
> > 				(geometry->bvol.URT.y
> > 				 - geometry->bvol.LLB.y),
> > 				precision,
> > 				(geometry->bvol.URT.x
> > 				 - geometry->bvol.LLB.x)*-1);
> > 		}
> > 		else
> > 		{
> > 			mem_size = MAX_DIGS_DOUBLE*4+3+1;
> > 			pfree(result);
> > 			result = (char *) palloc(mem_size);
> > 			// 4 double digits + 3 spaces +null
> >
> > 			sprintf(result, "%.*f %.*f %.*f %.*f",
> > 				precision,
> > 				geometry->bvol.LLB.x,
> > 				precision,
> > 				geometry->bvol.URT.y*-1,
> > 				precision,
> > 				(geometry->bvol.URT.x -
> > geometry->bvol.LLB.x),
> > 				precision,
> > 				(geometry->bvol.URT.y -
> > geometry->bvol.LLB.y)
> > 				);
> > 		}
> > 		return result;
> > 	}
> >
> > 	// no more warnings on compiletime
> > 	sprintf(result,"%s", "");
> >
> > 	if (geometry->type == COLLECTIONTYPE)
> > 	{
> > 		sprintf(result, "GEOMETRYCOLLECTION not yet supported");
> > 		return result;
> > 	}
> >
> > 	//where are the objects?
> > 	offsets = (int32 *) ( ((char *) &(geometry->objType[0] ))
> > 			+ sizeof(int32) * geometry->nobjs ) ;
> >
> > 	for(t=0;t<geometry->nobjs; t++)  //for each object
> > 	{
> > 		obj = (char *) geometry +offsets[t] ;
> >
> > 		if (geometry->objType[t] == 1)   //POINT
> > 		{
> > 			point = (POINT3D *) obj;
> > 			size +=MAX_DIGS_DOUBLE*3 + 2 +10  ;
> > 			//make memory bigger
> > 			result = repalloc(result, size );
> >
> > 			if (!(first_sub_obj))
> > 			{
> > 				// next circle ...
> > 				strcat(result,",");
> > 			}
> > 			else
> > 			{
> > 				first_sub_obj = FALSE;
> > 			}
> > 			if (svgrel == 1)
> > 			{
> > 				//render circle
> > 				print_svg_coords(result, point, precision);
> > 			}
> > 			else
> > 			{
> > 				//render circle
> > 				print_svg_circle(result, point, precision);
> > 			}
> >
> > 		}
> > 		if (geometry->objType[t] == 2)	//LINESTRING
> > 		{
> > 			line = (LINE3D *) obj;
> >
> > 			size +=(MAX_DIGS_DOUBLE*3+5)*line->npoints +12+3;
> > 			result = repalloc(result, size );
> >
> > 			// start path with moveto
> > 			strcat(result, "M ");
> >
> > 			if (svgrel == 1)
> > 				print_svg_path_rel(
> > 						result,
> > 						&line->points[0],
> > 						line->npoints,
> > 						precision
> > 						);
> > 			else
> > 				print_svg_path_abs(
> > 						result,
> > 						&line->points[0],
> > 						line->npoints,
> > 						precision
> > 						);
> >
> > 			strcat(result," ");
> > 		}
> > 		if (geometry->objType[t] == 3)	//POLYGON
> > 		{
> > 			polygon = (POLYGON3D *) obj;
> > 			pt_off = 0;	//where is the first point
> > in this ring?
> >
> > 			//where are the points
> > 			pts = (POINT3D *)
> > 				((char
> > *)&(polygon->npoints[polygon->nrings]));
> > 			pts = (POINT3D *) MAXALIGN(pts);
> >
> > 			npts = 0;
> > 			for (u=0; u< polygon->nrings ; u++)
> > 				npts += polygon->npoints[u];
> >
> > 			size += (MAX_DIGS_DOUBLE*3+3)
> > 				* npts + 5* polygon->nrings;
> > 			result = repalloc(result, size );
> >
> > 			for (u=0; u< polygon->nrings ; u++)  //for each ring
> > 			{
> > 				strcat(result,"M ");	//begin ring
> > 				if (svgrel == 1)
> > 					print_svg_path_rel(result,
> > 							&pts[pt_off] ,
> > 							polygon->npoints[u],
> > 							precision);
> > 				else
> > 					print_svg_path_abs(result,
> > 							&pts[pt_off],
> > 							polygon->npoints[u],
> > 							precision);
> >
> > 				//where is first point of next ring?
> > 				pt_off = pt_off + polygon->npoints[u];
> > 				strcat(result," ");	//end ring
> > 			}
> > 		}
> > 	}
> > 	return(result);
> > }
> >
> >
> > void print_svg_coords(char *result, POINT3D *pt, int precision)
> > {
> > 	char	temp[MAX_DIGS_DOUBLE*3 +12];
> >
> > 	if ( (pt == NULL) || (result == NULL) )
> > 		return;
> >
> > 	sprintf(temp, "x=\"%.*f\" y=\"%.*f\"",
> > 			precision, pt->x,
> > 			precision, pt->y*-1);
> > 	strcat(result,temp);
> > }
> >
> >
> > void print_svg_circle(char *result, POINT3D *pt, int precision)
> > {
> > 	char	temp[MAX_DIGS_DOUBLE*3 +12];
> >
> > 	if ( (pt == NULL) || (result == NULL) )
> > 		return;
> >
> > 	sprintf(temp, "cx=\"%.*f\" cy=\"%.*f\"",
> > 			precision, pt->x,
> > 			precision, pt->y*-1);
> > 	strcat(result,temp);
> > }
> >
> >
> > void print_svg_path_abs(char *result, POINT3D *pt ,int npoints, int
> > precision){
> > 	int	u;
> >
> > 	result += strlen(result);
> > 	for (u=0;u<npoints;u++)
> > 	{
> > 		if (u != 0)
> > 		{
> > 			result[0] = ' ';
> > 			result++;
> > 		}
> > 		result+= sprintf(result,"%.*f %.*f",
> > 				precision, pt[u].x,
> > 				precision, pt[u].y*-1);
> > 	}
> > }
> >
> >
> > void print_svg_path_rel(char *result, POINT3D *pt ,int npoints, int
> > precision){
> > 	int	u;
> >
> > 	result += strlen(result);
> > 	for (u=0;u<npoints;u++)
> > 	{
> > 		if (u == 0)
> > 		{
> > 			result+= sprintf(result,"%.*f %.*f l",
> > 					precision, pt[u].x,
> > 					precision, pt[u].y*-1);
> > 		}
> > 		else
> > 		{
> > 			result+= sprintf(result," %.*f %.*f",
> > 					precision, (pt[u].x-pt[u-1].x),
> > 					precision, (pt[u].y-pt[u-1].y)*-1);
> > 		}
> > 	}
> > }
> >
> >
> >
> >
> >
> > =========================== assvg.h.in ================================
> >
> > Datum assvg_geometry(PG_FUNCTION_ARGS);
> > char *geometry_to_svg(GEOMETRY  *geometry, int svgrel, int precision);
> > void print_svg_coords(char *result, POINT3D *pt, int precision);
> > void print_svg_circle(char *result, POINT3D *pt, int precision);
> > void print_svg_path_abs(char *result, POINT3D *pt ,int npoints, int
> > precision); void print_svg_path_rel(char *result, POINT3D *pt ,int
> > npoints, int precision);
> >
> >
> > =========================== assvg.sql.in ==============================
> >
> > CREATE FUNCTION assvg(geometry)
> > 	RETURNS TEXT
> > 	AS '@MODULE_FILENAME@','assvg_geometry'
> > 	LANGUAGE 'c'  with (isstrict);
> >
> > CREATE FUNCTION assvg(geometry,int4)
> > 	RETURNS TEXT
> > 	AS '@MODULE_FILENAME@','assvg_geometry'
> > 	LANGUAGE 'c'  with (isstrict);
> >
> > CREATE FUNCTION assvg(geometry,int4,int4)
> > 	RETURNS TEXT
> > 	AS '@MODULE_FILENAME@','assvg_geometry'
> > 	LANGUAGE 'c'  with (isstrict);
> >
> >
> > =====================================================================
> >
> > HTH :)
> >
> > --
> > Ol
> >
> > _______________________________________________
> > postgis-users mailing list
> > postgis-users at postgis.refractions.net
> > http://postgis.refractions.net/mailman/listinfo/postgis-users
>
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