void convert(mapnik::grid::data_type const & grid, image_type & image) const
{
for (std::size_t y = 0; y < grid.height(); ++y)
{
mapnik::grid::value_type const * grid_row = grid.get_row(y);
image_type::pixel_type * image_row = image.get_row(y);
for (std::size_t x = 0; x < grid.width(); ++x)
{
mapnik::grid::value_type val = grid_row[x];
if (val == mapnik::grid::base_mask)
{
image_row[x] = 0;
continue;
}
if (val < 0)
{
throw std::runtime_error("grid renderer: feature id is negative.");
}
val *= 100;
if (val > 0x00ffffff)
{
throw std::runtime_error("grid renderer: feature id is too high.");
}
image_row[x] = val | 0xff000000;
}
}
}
static inline void scale_grid(mapnik::grid::data_type & target,
const mapnik::grid::data_type & source,
double x_off_f, double y_off_f)
{
int source_width=source.width();
int source_height=source.height();
int target_width=target.width();
int target_height=target.height();
if (source_width<1 || source_height<1 ||
target_width<1 || target_height<1) return;
int x=0,y=0,xs=0,ys=0;
int tw2 = target_width/2;
int th2 = target_height/2;
int offs_x = rint((source_width-target_width-x_off_f*2*source_width)/2);
int offs_y = rint((source_height-target_height-y_off_f*2*source_height)/2);
unsigned yprt(0);
unsigned yprt1(0);
unsigned xprt(0);
unsigned xprt1(0);
//no scaling or subpixel offset
if (target_height == source_height && target_width == source_width && offs_x == 0 && offs_y == 0){
for (y=0;y<target_height;++y)
target.setRow(y,source.getRow(y),target_width);
return;
}
for (y=0;y<target_height;++y)
{
ys = (y*source_height+offs_y)/target_height;
int ys1 = ys+1;
if (ys1>=source_height)
ys1--;
if (ys<0)
ys=ys1=0;
if (source_height/2<target_height)
yprt = (y*source_height+offs_y)%target_height;
else
yprt = th2;
yprt1 = target_height-yprt;
for (x=0;x<target_width;++x)
{
xs = (x*source_width+offs_x)/target_width;
if (source_width/2<target_width)
xprt = (x*source_width+offs_x)%target_width;
else
xprt = tw2;
xprt1 = target_width-xprt;
int xs1 = xs+1;
if (xs1>=source_width)
xs1--;
if (xs<0)
xs=xs1=0;
mapnik::grid::value_type a = source(xs,ys);
mapnik::grid::value_type b = source(xs1,ys);
mapnik::grid::value_type c = source(xs,ys1);
mapnik::grid::value_type d = source(xs1,ys1);
if ((a > 0) && (b > 0))
target(x,y) = b;
else if ((c > 0) && (d > 0))
target(x,y) = d;
else
target(x,y) = a;
}
}
}