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#include <mbgl/geometry/dem_pyramid.hpp>
namespace mbgl {
void DEMPyramid::buildLevels() {
while (true) {
auto& prev = levels.back();
const int32_t width = std::ceil(prev.width / 2);
const int32_t height = std::ceil(prev.height / 2);
const int32_t border = std::max<int32_t>(std::ceil(prev.border / 2), 1);
if (width == 1 || height == 1) {
break;
}
Level next(width, height, border);
prev.resample(next);
levels.emplace_back(std::move(next));
}
// Build remaining two levels. They aren't actually used in rendering, but we
// need them for OpenGL's mipmapping feature.
levels.emplace_back(2, 2, 0);
levels.emplace_back(1, 1, 0);
}
DEMPyramid::Level::Level(int32_t width_, int32_t height_, size_t border_)
: width(width_),
height(height_),
border(border_),
stride(width + 2 * border),
image({ static_cast<uint32_t>(width + 2 * border),
static_cast<uint32_t>(height + 2 * border) }) {
assert(width > 0);
assert(height > 0);
std::memset(image.data.get(), 0, image.bytes());
}
void DEMPyramid::Level::resample(Level& target) {
for (int32_t y = 0; y < target.height; y++) {
const int32_t fy = y * 2;
for (int32_t x = 0; x < target.width; x++) {
const int32_t fx = x * 2;
target.set(x, y, (get(fx, fy) + get(fx + 1, fy) + get(fx, fy + 1) + get(fx + 1, fy + 1)) / 4);
}
}
}
} // namespace mbgl
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