/**********************************************************************
* OGRIntersectPointPolygon()
*
* Instead of using ring orientation we count the number of parts the
* point falls in. If odd the point is in the polygon, if 0 or even
* then the point is in a hole or completely outside.
*
* Returns TRUE is point is inside polygon, FALSE otherwise
*
* Adapted version of msIntersectPointPolygon() from MapServer's mapsearch.c
**********************************************************************/
GBool OGRIntersectPointPolygon(OGRPoint *poPoint, OGRPolygon *poPoly)
{
GBool status = FALSE;
for( int i = 0; i<OGR_NUM_RINGS(poPoly); i++ )
{
if (OGRPointInRing(poPoint, OGR_GET_RING(poPoly, i)))
{
/* ok, the point is in a line */
status = !status;
}
}
return status;
}
int OGRGetCentroid(OGRPolygon *poPoly, OGRPoint *poCentroid)
{
int i,j;
double cent_weight_x=0.0, cent_weight_y=0.0;
double len, total_len=0;
for(i=0; i<OGR_NUM_RINGS(poPoly); i++)
{
double x1, y1, x2, y2;
OGRLinearRing *poRing = OGR_GET_RING(poPoly, i);
x2 = poRing->getX(0);
y2 = poRing->getY(0);
for(j=1; j<poRing->getNumPoints(); j++)
{
x1 = x2;
y1 = y2;
x2 = poRing->getX(j);
y2 = poRing->getY(j);
len = sqrt( pow((x2-x1),2) + pow((y2-y1),2) );
cent_weight_x += len * ((x1 + x2)/2.0);
cent_weight_y += len * ((y1 + y2)/2.0);
total_len += len;
}
}
if(total_len == 0)
return(OGRERR_FAILURE);
poCentroid->setX( cent_weight_x / total_len );
poCentroid->setY( cent_weight_y / total_len );
return OGRERR_NONE;
}
int OGRPolygonLabelPoint(OGRPolygon *poPoly, OGRPoint *poLabelPoint)
{
double slope;
OGRRawPoint point1, point2;
int i, j, k, nfound;
double x, y, *xintersect, temp;
double hi_y, lo_y;
int wrong_order, n;
double len, max_len=0;
double skip;
OGREnvelope oEnv;
if (poPoly == NULL)
return OGRERR_FAILURE;
poPoly->getEnvelope(&oEnv);
poLabelPoint->setX((oEnv.MaxX + oEnv.MinX)/2.0);
poLabelPoint->setY((oEnv.MaxY + oEnv.MinY)/2.0);
//if(get_centroid(p, lp, &miny, &maxy) == -1) return(-1);
if(OGRIntersectPointPolygon(poLabelPoint, poPoly) == TRUE) /* cool, done */
return OGRERR_NONE;
/* do it the hard way - scanline */
skip = (oEnv.MaxY - oEnv.MinY)/NUM_SCANLINES;
n=0;
for(j=0; j<OGR_NUM_RINGS(poPoly); j++)
{
/* count total number of points */
n += OGR_GET_RING(poPoly, j)->getNumPoints();
}
xintersect = (double *)calloc(n, sizeof(double));
if (xintersect == NULL)
return OGRERR_FAILURE;
for(k=1; k<=NUM_SCANLINES; k++)
{
/* sample the shape in the y direction */
y = oEnv.MaxY - k*skip;
/* need to find a y that won't intersect any vertices exactly */
hi_y = y - 1; /* first initializing lo_y, hi_y to be any 2 pnts on either side of lp->y */
lo_y = y + 1;
for(j=0; j<OGR_NUM_RINGS(poPoly); j++)
{
OGRLinearRing *poRing = OGR_GET_RING(poPoly,j);
if((lo_y < y) && (hi_y >= y))
break; /* already initialized */
for(i=0; i < poRing->getNumPoints(); i++)
{
if((lo_y < y) && (hi_y >= y))
break; /* already initialized */
if(poRing->getY(i) < y)
lo_y = poRing->getY(i);
if(poRing->getY(i) >= y)
hi_y = poRing->getY(i);
}
}
n=0;
for(j=0; j<OGR_NUM_RINGS(poPoly); j++)
{
OGRLinearRing *poRing = OGR_GET_RING(poPoly,j);
for(i=0; i < poRing->getNumPoints(); i++)
{
if((poRing->getY(i) < y) &&
((y - poRing->getY(i)) < (y - lo_y)))
lo_y = poRing->getY(i);
if((poRing->getY(i) >= y) &&
((poRing->getY(i) - y) < (hi_y - y)))
hi_y = poRing->getY(i);
}
}
if(lo_y == hi_y)
return OGRERR_FAILURE;
else
y = (hi_y + lo_y)/2.0;
nfound = 0;
for(j=0; j<OGR_NUM_RINGS(poPoly); j++) /* for each line */
{
OGRLinearRing *poRing = OGR_GET_RING(poPoly,j);
point1.x = poRing->getX(poRing->getNumPoints()-1);
point1.y = poRing->getY(poRing->getNumPoints()-1);
for(i=0; i < poRing->getNumPoints(); i++)
{
point2.x = poRing->getX(i);
point2.y = poRing->getY(i);
if(EDGE_CHECK(point1.y, y, point2.y) == CLIP_MIDDLE)
{
if(point1.y == point2.y)
continue; /* ignore horizontal edges */
else
slope = (point2.x - point1.x) / (point2.y - point1.y);
x = point1.x + (y - point1.y)*slope;
xintersect[nfound++] = x;
} /* End of checking this edge */
point1 = point2; /* Go on to next edge */
}
} /* Finished the scanline */
/* First, sort the intersections */
do
{
wrong_order = 0;
for(i=0; i < nfound-1; i++)
{
if(xintersect[i] > xintersect[i+1])
{
wrong_order = 1;
SWAP(xintersect[i], xintersect[i+1], temp);
}
}
} while(wrong_order);
/* Great, now find longest span */
point1.y = point2.y = y;
for(i=0; i < nfound; i += 2)
{
point1.x = xintersect[i];
point2.x = xintersect[i+1];
/* len = length(point1, point2); */
len = ABS((point2.x - point1.x));
if(len > max_len)
{
max_len = len;
poLabelPoint->setX( (point1.x + point2.x)/2 );
poLabelPoint->setY( y );
}
}
}
free(xintersect);
/* __TODO__ Bug 673
* There seem to be some polygons for which the label is returned
* completely outside of the polygon's MBR and this messes the
* file bounds, etc.
* Until we find the source of the problem, we'll at least validate
* the label point to make sure that it overlaps the polygon MBR.
*/
if( poLabelPoint->getX() < oEnv.MinX
|| poLabelPoint->getY() < oEnv.MinY
|| poLabelPoint->getX() > oEnv.MaxX
|| poLabelPoint->getY() > oEnv.MaxY )
{
// Reset label coordinates to center of MBR, just in case
poLabelPoint->setX((oEnv.MaxX + oEnv.MinX)/2.0);
poLabelPoint->setY((oEnv.MaxY + oEnv.MinY)/2.0);
// And return an error
return OGRERR_FAILURE;
}
if(max_len > 0)
return OGRERR_NONE;
else
return OGRERR_FAILURE;
}