/*
** Calculate the approximate scale based on a few parameters. Note that this assumes the scale is
** the same in the x direction as in the y direction, so run msAdjustExtent(...) first.
*/
int msCalculateScale(rectObj extent, int units, int width, int height, double resolution, double *scale)
{
double md, gd, center_y;
/* if((extent.maxx == extent.minx) || (extent.maxy == extent.miny)) */
if(!MS_VALID_EXTENT(extent)) {
msSetError(MS_MISCERR, "Invalid image extent, minx=%lf, miny=%lf, maxx=%lf, maxy=%lf.", "msCalculateScale()", extent.minx, extent.miny, extent.maxx, extent.maxy);
return(MS_FAILURE);
}
if((width <= 0) || (height <= 0)) {
msSetError(MS_MISCERR, "Invalid image width or height.", "msCalculateScale()");
return(MS_FAILURE);
}
switch (units) {
case(MS_DD):
case(MS_METERS):
case(MS_KILOMETERS):
case(MS_MILES):
case(MS_NAUTICALMILES):
case(MS_INCHES):
case(MS_FEET):
center_y = (extent.miny+extent.maxy)/2.0;
md = (width-1)/(resolution*msInchesPerUnit(units, center_y)); /* remember, we use a pixel-center to pixel-center extent, hence the width-1 */
gd = extent.maxx - extent.minx;
*scale = gd/md;
break;
default:
*scale = -1; /* this is not an error */
break;
}
return(MS_SUCCESS);
}
int msMapSetExtent( mapObj *map,
double minx, double miny, double maxx, double maxy)
{
map->extent.minx = minx;
map->extent.miny = miny;
map->extent.maxx = maxx;
map->extent.maxy = maxy;
if (!MS_VALID_EXTENT(map->extent)) {
msSetError(MS_MISCERR, "Given map extent is invalid. Check that it " \
"is in the form: minx, miny, maxx, maxy", "setExtent()");
return MS_FAILURE;
}
map->cellsize = msAdjustExtent(&(map->extent), map->width,
map->height);
/* if the map size is also set, recompute scale, ignore errors? */
if( map->width != -1 || map->height != -1 )
msCalculateScale(map->extent, map->units, map->width, map->height,
map->resolution, &(map->scaledenom));
return msMapComputeGeotransform( map );
}
