/**
We calculate the effective area for the first time
*/
void ptarray_calc_areas(EFFECTIVE_AREAS *ea, int avoid_collaps, int set_area, double trshld)
{
LWDEBUG(2, "Entered ptarray_calc_areas");
int i;
int npoints=ea->inpts->npoints;
int is3d = FLAGS_GET_Z(ea->inpts->flags);
double area;
const double *P1;
const double *P2;
const double *P3;
P1 = (double*)getPoint_internal(ea->inpts, 0);
P2 = (double*)getPoint_internal(ea->inpts, 1);
/*The first and last point shall always have the maximum effective area. We use float max to not make trouble for bbox*/
ea->initial_arealist[0].area=ea->initial_arealist[npoints-1].area=FLT_MAX;
ea->res_arealist[0]=ea->res_arealist[npoints-1]=FLT_MAX;
ea->initial_arealist[0].next=1;
ea->initial_arealist[0].prev=0;
for (i=1;i<(npoints)-1;i++)
{
ea->initial_arealist[i].next=i+1;
ea->initial_arealist[i].prev=i-1;
P3 = (double*)getPoint_internal(ea->inpts, i+1);
if(is3d)
area=triarea3d(P1, P2, P3);
else
area=triarea2d(P1, P2, P3);
LWDEBUGF(4,"Write area %lf to point %d on address %p",area,i,&(ea->initial_arealist[i].area));
ea->initial_arealist[i].area=area;
P1=P2;
P2=P3;
}
ea->initial_arealist[npoints-1].next=npoints-1;
ea->initial_arealist[npoints-1].prev=npoints-2;
for (i=1;i<(npoints)-1;i++)
{
ea->res_arealist[i]=FLT_MAX;
}
tune_areas(ea,avoid_collaps,set_area, trshld);
return ;
}
/**
* We calculate the effective area for the first time
*/
void ptarray_calc_areas( EFFECTIVE_AREAS *ea, int avoid_collaps, int set_area, double trshld )
{
//LWDEBUG( 2, "Entered ptarray_calc_areas" );
int i;
int npoints = ea->inpts.size();
double area;
QgsPointV2 P1;
QgsPointV2 P2;
QgsPointV2 P3;
P1 = ea->inpts.at( 0 );
P2 = ea->inpts.at( 1 );
// The first and last point shall always have the maximum effective area. We use float max to not make trouble for bbox
ea->initial_arealist[0].area = ea->initial_arealist[npoints - 1].area = FLT_MAX;
ea->res_arealist[0] = ea->res_arealist[npoints - 1] = FLT_MAX;
ea->initial_arealist[0].next = 1;
ea->initial_arealist[0].prev = 0;
for ( i = 1; i < ( npoints ) - 1; i++ )
{
ea->initial_arealist[i].next = i + 1;
ea->initial_arealist[i].prev = i - 1;
P3 = ea->inpts.at( i + 1 );
if ( ea->is3d )
area = triarea3d( P1, P2, P3 );
else
area = triarea2d( P1, P2, P3 );
//LWDEBUGF( 4, "Write area %lf to point %d on address %p", area, i, &( ea->initial_arealist[i].area ) );
ea->initial_arealist[i].area = area;
P1 = P2;
P2 = P3;
}
ea->initial_arealist[npoints - 1].next = npoints - 1;
ea->initial_arealist[npoints - 1].prev = npoints - 2;
for ( i = 1; i < ( npoints ) - 1; i++ )
{
ea->res_arealist[i] = FLT_MAX;
}
tune_areas( ea, avoid_collaps, set_area, trshld );
}
/**
To get the effective area, we have to check what area a point results in when all smaller areas are eliminated
*/
static void tune_areas(EFFECTIVE_AREAS *ea, int avoid_collaps, int set_area, double trshld)
{
LWDEBUG(2, "Entered tune_areas");
const double *P1;
const double *P2;
const double *P3;
double area;
int go_on=1;
double check_order_min_area = 0;
int npoints=ea->inpts->npoints;
int i;
int current, before_current, after_current;
MINHEAP tree = initiate_minheap(npoints);
int is3d = FLAGS_GET_Z(ea->inpts->flags);
/*Add all keys (index in initial_arealist) into minheap array*/
for (i=0;i<npoints;i++)
{
tree.key_array[i]=ea->initial_arealist+i;
LWDEBUGF(2, "add nr %d, with area %lf, and %lf",i,ea->initial_arealist[i].area, tree.key_array[i]->area );
}
tree.usedSize=npoints;
/*order the keys by area, small to big*/
qsort(tree.key_array, npoints, sizeof(void*), cmpfunc);
/*We have to put references to our tree in our point-list*/
for (i=0;i<npoints;i++)
{
((areanode*) tree.key_array[i])->treeindex=i;
LWDEBUGF(4,"Check ordering qsort gives, area=%lf and belong to point %d",((areanode*) tree.key_array[i])->area, tree.key_array[i]-ea->initial_arealist);
}
/*Ok, now we have a minHeap, just need to keep it*/
/*for (i=0;i<npoints-1;i++)*/
i=0;
while (go_on)
{
/*Get a reference to the point with the currently smallest effective area*/
current=minheap_pop(&tree, ea->initial_arealist)-ea->initial_arealist;
/*We have found the smallest area. That is the resulting effective area for the "current" point*/
if (i<npoints-avoid_collaps)
ea->res_arealist[current]=ea->initial_arealist[current].area;
else
ea->res_arealist[current]=FLT_MAX;
if(ea->res_arealist[current]<check_order_min_area)
lwerror("Oh no, this is a bug. For some reason the minHeap returned our points in the wrong order. Please file a ticket in PostGIS ticket system, or send a mial at the mailing list.Returned area = %lf, and last area = %lf",ea->res_arealist[current],check_order_min_area);
check_order_min_area=ea->res_arealist[current];
/*The found smallest area point is now regarded as elimnated and we have to recalculate the area the adjacent (ignoring earlier elimnated points) points gives*/
/*FInd point before and after*/
before_current=ea->initial_arealist[current].prev;
after_current=ea->initial_arealist[current].next;
P2= (double*)getPoint_internal(ea->inpts, before_current);
P3= (double*)getPoint_internal(ea->inpts, after_current);
/*Check if point before current point is the first in the point array. */
if(before_current>0)
{
P1= (double*)getPoint_internal(ea->inpts, ea->initial_arealist[before_current].prev);
if(is3d)
area=triarea3d(P1, P2, P3);
else
area=triarea2d(P1, P2, P3);
ea->initial_arealist[before_current].area = FP_MAX(area,ea->res_arealist[current]);
minheap_update(&tree, ea->initial_arealist, ea->initial_arealist[before_current].treeindex);
}
if(after_current<npoints-1)/*Check if point after current point is the last in the point array. */
{
P1=P2;
P2=P3;
P3= (double*)getPoint_internal(ea->inpts, ea->initial_arealist[after_current].next);
if(is3d)
area=triarea3d(P1, P2, P3);
else
area=triarea2d(P1, P2, P3);
ea->initial_arealist[after_current].area = FP_MAX(area,ea->res_arealist[current]);
minheap_update(&tree, ea->initial_arealist, ea->initial_arealist[after_current].treeindex);
}
/*rearrange the nodes so the eliminated point will be ingored on the next run*/
ea->initial_arealist[before_current].next = ea->initial_arealist[current].next;
ea->initial_arealist[after_current].prev = ea->initial_arealist[current].prev;
/*Check if we are finnished*/
if((!set_area && ea->res_arealist[current]>trshld) || (ea->initial_arealist[0].next==(npoints-1)))
go_on=0;
i++;
};
destroy_minheap(tree);
return;
}
