make_any_blind_raster
Prototype
template<class Raster>
any_blind_raster make_any_blind_raster(Raster raster)
Description
Creates an any_blind_raster that wraps around a raster. This is a form of type_erasure as the value_type of a RasterView is known at compile time, but the value_type of an any_blind_raster is only known at run-time.
Definition
<pronto/raster/any_blind_raster.h> (open in Github)
Requirements on types
Raster implements the RasterView concept.
Preconditions
The value type of the input Raster is one of any_blind_raster supported types: bool, short, unsigned int, int, unsigned short, unsigned char, float, double
Complexity
O(1)
Example of use
//example_any_blind_raster.cpp
#include <pronto/raster/any_blind_raster.h>
#include <pronto/raster/io.h>
#include <pronto/raster/plot_raster.h>
#include <pronto/raster/transform_raster_view.h>
namespace pr = pronto::raster;
// the following function shows how any_blind_raster is used to decide
// at runtime which value_type to use
template<class Raster>
pr::any_blind_raster optionally_take_square_root(Raster raster, bool take_root)
{
using input_value_type = typename pr::traits<Raster>::value_type;
if (take_root) {
// value type will be return type of sqrt<input_value_type>
auto square_rooted = pr::transform(std::sqrt<input_value_type>, raster);
return pr::make_any_blind_raster(square_rooted);
}
else {
// value_type will be traits<Raster>::value_type
return pr::make_any_blind_raster(raster);
}
}
int main()
{
auto raster = pr::create_temp<int>( 3, 4, GDT_Byte);
auto i = 0;
for (auto&& v : raster) {
i = (i + 3) % 7;
v = i;
}
pr::any_blind_raster a = optionally_take_square_root(raster, false);
pr::any_blind_raster b = optionally_take_square_root(raster, true);
plot_raster(a);
plot_raster(b);
return 0;
}
Output:
Rows: 3, Cols: 4, Value type: int
3 6 2 5
1 4 0 3
6 2 5 1
Rows: 3, Cols: 4, Value type: double
1.73205 2.44949 1.41421 2.23607
1 2 0 1.73205
2.44949 1.41421 2.23607 1
Notes
Accessing the values in an any_blind raster is slower than accessing values in the original raster (factor ~2).