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igd_demosaic_generator.cpp
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igd_demosaic_generator.cpp
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//
// A Halide implementation of "A Low Complexity Color Demosaicing Algorithm Based on Integrated Gradient" by
// King-Hong Chung and Yuk-Hee Chan:
//
// http://www.eie.polyu.edu.hk/~enyhchan/J-JEI-Low_complexity_color_demosaicing_algorithm_based_on_IG.pdf
//
#include <Halide.h>
#include <HalideRuntime.h>
using namespace Halide;
/*
param: Image parameters (mainly type) to compile for.
layout: see below
out_type: the type to cast to at the end
layouts: RGGB, GRBG, GBRG, BGGR
*/
namespace {
class IgdDemosaic : public Halide::Generator<IgdDemosaic> {
public:
ImageParam in_{UInt(16), 2, "input"};
Param <uint8_t> layout{"layout"};
Var x, y, c;
Func build() {
x = Var("x");
y = Var("y");
c = Var("c");
Expr alpha = 1.0f;
Func input = Func("input");
input(x, y) = cast(Float(32), in_(
clamp(x, 0, in_.width() - 1),
clamp(y, 0, in_.height() - 1)
));
//#### Horizontal ####
Func cd_horizontal = Func("cd_horizontal");
cd_horizontal(x, y) = input(x, y) - (input(x - 1, y) + input(x + 1, y)) / 2;
Func cd_gradient_horizontal_raw = Func("cd_gradient_horizontal_raw");
cd_gradient_horizontal_raw(x, y) = (
absd(cd_horizontal(x, y), cd_horizontal(x + 1, y)) +
absd(cd_horizontal(x, y), cd_horizontal(x - 1, y))) / 2.0f;
Func cd_gradient_horizontal = Func("cd_gradient_horizontal");
cd_gradient_horizontal(x, y) = (cd_gradient_horizontal_raw(x - 1, y) + cd_gradient_horizontal_raw(x, y) +
cd_gradient_horizontal_raw(x + 1, y)) / 3.0f;
Func ci_gradient_plane_horizontal = Func("ci_gradient_plane_horizontal");
ci_gradient_plane_horizontal(x, y) = absd(input(x, y), input(x + 2, y));
Func cd_gradient_plane_horizontal = Func("cd_gradient_plane_horizontal");
cd_gradient_plane_horizontal(x, y) = cd_gradient_horizontal(x + 1, y);
Func ig_horizontal = Func("ig_horizontal");
ig_horizontal(x, y) = ci_gradient_plane_horizontal(x, y) + alpha * (
2 * cd_gradient_plane_horizontal(x, y) +
cd_gradient_plane_horizontal(x, y - 1) +
cd_gradient_plane_horizontal(x, y + 1));
//#### Vertical ####
Func cd_vertical = Func("cd_vertical");
cd_vertical(x, y) = input(x, y) - (input(x, y - 1) + input(x, y + 1)) / 2;
Func cd_gradient_vertical_raw = Func("cd_gradient_vertical_raw");
cd_gradient_vertical_raw(x, y) = (
absd(cd_vertical(x, y), cd_vertical(x, y + 1)) +
absd(cd_vertical(x, y), cd_vertical(x, y - 1))) / 2.0f;
Func cd_gradient_vertical = Func("cd_gradient_vertical");
cd_gradient_vertical(x, y) = (cd_gradient_vertical_raw(x, y - 1) + cd_gradient_vertical_raw(x, y) +
cd_gradient_vertical_raw(x, y + 1)) / 3.0f;
Func ci_gradient_plane_vertical = Func("ci_gradient_plane_vertical");
ci_gradient_plane_vertical(x, y) = absd(input(x, y), input(x, y + 2));
Func cd_gradient_plane_vertical = Func("cd_gradient_plane_vertical");
cd_gradient_plane_vertical(x, y) = cd_gradient_vertical(x, y + 1);
Func ig_vertical = Func("ig_vertical");
ig_vertical(x, y) = ci_gradient_plane_vertical(x, y) + alpha * (
2 * cd_gradient_plane_vertical(x, y) +
cd_gradient_plane_vertical(x - 1, y) +
cd_gradient_plane_vertical(x + 1, y));
//#### Interpolation ####
Func green_horizontal = Func("green_horizontal");
green_horizontal(x, y) = ((input(x - 1, y) + input(x + 1, y)) / 2.0f) +
(2.0f * input(x, y) - input(x - 2, y) - input(x + 2, y)) / 4.0f;
Func green_vertical = Func("green_vertical");
green_vertical(x, y) = ((input(x, y - 1) + input(x, y + 1)) / 2.0f) +
(2.0f * input(x, y) - input(x, y - 2) - input(x, y + 2)) / 4.0f;
Func green_neither = Func("green_neither");
green_neither(x, y) = (green_horizontal(x, y) + green_vertical(x, y)) / 2.0f;
Func delta_h = Func("delta_h");
delta_h(x, y) = ig_horizontal(x, y) + ig_horizontal(x - 2, y);
Func delta_v = Func("delta_v");
delta_v(x, y) = ig_vertical(x, y) + ig_vertical(x, y - 2);
Func max_factor = Func("max_factor");
max_factor(x, y) = max(delta_h(x, y) / delta_v(x, y), delta_v(x, y) / delta_h(x, y));
float threshold = 1.7f;
Expr L = 3.0f;
Func go_to_pass1 = Func("go_to_pass1");
go_to_pass1(x, y) = select(
max_factor(x, y) == 1 or max_factor(x, y) > threshold, 1,
0
);
Func pass1 = Func("pass1");
pass1(x, y) = select(
delta_h(x, y) == delta_v(x, y), green_neither(x, y),
delta_h(x, y) > delta_v(x, y), green_vertical(x, y),
green_horizontal(x, y));
Func pmn_h = Func("pmn_h");
pmn_h(x, y) = select(
go_to_pass1(x, y) == 1, pass1(x, y) - input(x, y),
green_horizontal(x, y) - input(x, y)
);
Func pmn_v = Func("pmn_v");
pmn_v(x, y) = select(
go_to_pass1(x, y) == 1, pass1(x, y) - input(x, y),
green_vertical(x, y) - input(x, y)
);
Func pmn_d = Func("pmn_d");
pmn_d(x, y) = select(
go_to_pass1(x, y) == 1, pass1(x, y) - input(x, y),
green_neither(x, y) - input(x, y)
);
RDom tDom = RDom(-L, L + 1);
Func phi_h = Func("phi_h");
phi_h(x, y) = sum(absd(pmn_h(x, y), pmn_h(x - 2 * tDom.x, y)));
Func phi_v = Func("phi_v");
phi_v(x, y) = sum(absd(pmn_v(x, y), pmn_v(x, y - 2 * tDom.x)));
Func phi_d = Func("phi_d");
phi_d(x, y) = (
sum(absd(pmn_d(x, y), pmn_d(x - 2 * tDom.x, y))) +
sum(absd(pmn_d(x, y), pmn_d(x, y - 2 * tDom.x)))) / 2.0f;
Func smallest_phi = Func("smallest_phi");
smallest_phi(x, y) = Halide::min(phi_h(x, y), Halide::min(phi_v(x, y), phi_d(x, y)));
Func pass2 = Func("pass2");
pass2(x, y) = select(
go_to_pass1(x, y) == 1, pass1(x, y),
smallest_phi(x, y) == phi_h(x, y), green_horizontal(x, y),
smallest_phi(x, y) == phi_v(x, y), green_vertical(x, y),
green_neither(x, y)
);
// Layout definition
Func is_green = Func("is_green");
Expr xggb = (layout == 0) || (layout == 3);
is_green(x, y) = (
((x % 2 + y % 2 == 1) && xggb) ||
((x % 2 + y % 2 != 1) && !xggb)
);
Func is_red = Func("is_red");
is_red(x, y) = (
x % 2 + 2 * (y % 2) == layout
);
Func is_blue = Func("is_blue");
is_blue(x, y) = (
3 - (x % 2 + 2 * (y % 2)) == layout
);
Expr red_even = layout % 2 == 0;
Expr blue_even = !red_even;
Func green_unenhanced = Func("green_unenhanced");
green_unenhanced(x, y) = select(
is_green(x, y), input(x, y),
pass2(x, y));
Func w_e = Func("w_e");
w_e(x, y) = 1 / ig_horizontal(x, y);
Func w_w = Func("w_w");
w_w(x, y) = 1 / ig_horizontal(x - 2, y);
Func w_s = Func("w_s");
w_s(x, y) = 1 / ig_vertical(x, y);
Func w_n = Func("w_n");
w_n(x, y) = 1 / ig_vertical(x, y - 2);
Func w_se = Func("w_se");
w_se(x, y) = 1 / (ig_horizontal(x, y) + ig_vertical(x, y));
Func w_sw = Func("w_sw");
w_sw(x, y) = 1 / (ig_horizontal(x - 2, y) + ig_vertical(x, y));
Func w_ne = Func("w_ne");
w_ne(x, y) = 1 / (ig_horizontal(x, y) + ig_vertical(x, y - 2));
Func w_nw = Func("w_nw");
w_nw(x, y) = 1 / (ig_horizontal(x - 2, y) + ig_vertical(x, y - 2));
Func d_line_top = Func("d_line_top");
d_line_top(x, y) = green_unenhanced(x, y) - input(x, y);
Func d_squiggle_top = Func("d_squiggle_top");
d_squiggle_top(x, y) = (
w_e(x, y) * d_line_top(x + 2, y) +
w_w(x, y) * d_line_top(x - 2, y) +
w_s(x, y) * d_line_top(x, y + 2) +
w_n(x, y) * d_line_top(x, y - 2)) / (
w_e(x, y) + w_w(x, y) + w_s(x, y) + w_n(x, y)
);
Func d_hat_top_known = Func("d_hat_top_known");
Expr beta = Expr(0.33f);
d_hat_top_known(x, y) = beta * d_line_top(x, y) + (1.0f - beta) * d_squiggle_top(x, y);
Func d_hat_top_diagonal = Func("d_hat_top_diagonal");
d_hat_top_diagonal(x, y) = (
w_nw(x, y) * d_hat_top_known(x - 1, y - 1) +
w_ne(x, y) * d_hat_top_known(x + 1, y - 1) +
w_se(x, y) * d_hat_top_known(x + 1, y + 1) +
w_sw(x, y) * d_hat_top_known(x - 1, y + 1)) / (
w_nw(x, y) + w_ne(x, y) + w_se(x, y) + w_sw(x, y)
);
Func d_hat_top_g = Func("d_hat_top_g");
d_hat_top_g(x, y, c) = select(
// Determine whether known pixels for this colour are above or to the side
(x % 2 != c), (
w_e(x, y) * d_hat_top_diagonal(x + 1, y) +
w_w(x, y) * d_hat_top_diagonal(x - 1, y) +
w_s(x, y) * d_hat_top_known(x, y + 1) +
w_n(x, y) * d_hat_top_known(x, y - 1)
),
(
w_e(x, y) * d_hat_top_known(x + 1, y) +
w_w(x, y) * d_hat_top_known(x - 1, y) +
w_s(x, y) * d_hat_top_diagonal(x, y + 1) +
w_n(x, y) * d_hat_top_diagonal(x, y - 1)
)
) / (
w_e(x, y) + w_w(x, y) + w_s(x, y) + w_n(x, y)
);
Func green_debayer = Func("green_debayer");
green_debayer(x, y) = select(
is_green(x, y), input(x, y),
d_hat_top_known(x, y) + input(x, y));
Func red_debayer = Func("red_debayer");
red_debayer(x, y) = select(
is_red(x, y), input(x, y),
is_blue(x, y), green_debayer(x, y) - d_hat_top_diagonal(x, y),
green_debayer(x, y) - d_hat_top_g(x, y, red_even)
);
Func blue_debayer = Func("blue_debayer");
blue_debayer(x, y) = select(
is_blue(x, y), input(x, y),
is_red(x, y), green_debayer(x, y) - d_hat_top_diagonal(x, y),
green_debayer(x, y) - d_hat_top_g(x, y, blue_even)
);
Func debayer = Func("debayer");
debayer(x, y, c) = select(
c == 1, green_debayer(x, y),
c == 0, red_debayer(x, y),
blue_debayer(x, y)
);
Func output = Func("output");
output(x, y, c) = cast(UInt(16), debayer(x, y, c));
output.bound(x, 0, (in_.width() / 2) * 2);
output.bound(y, 0, (in_.height() / 2) * 2);
output.bound(c, 0, 3);
Target target = get_target();
if(!target.has_gpu_feature()) {
Var x_outer, y_outer, x_inner, y_inner, tile_index;
x_outer = Var("x_outer");
y_outer = Var("y_outer");
x_inner = Var("x_inner");
y_inner = Var("y_inner");
tile_index = Var("tile_index");
output.reorder_storage(c, x, y).reorder(c, x, y);
output.unroll(c);
output.compute_root();
output.tile(x, y, x_outer, y_outer, x_inner, y_inner, 128, 128);
output.fuse(x_outer, y_outer, tile_index);
output.parallel(tile_index);
output.vectorize(x_inner, 8);
input.compute_at(output, tile_index);
input.unroll(x, 2).unroll(y, 2);
input.vectorize(x, 16);
ig_horizontal.compute_at(output, tile_index);
ig_horizontal.vectorize(x, 8);
cd_gradient_plane_horizontal.compute_at(ig_horizontal, Var::outermost());
cd_gradient_plane_horizontal.vectorize(x, 16);
ig_vertical.compute_at(output, tile_index);
ig_vertical.vectorize(x, 8);
cd_gradient_plane_vertical.compute_at(ig_vertical, Var::outermost());
cd_gradient_plane_vertical.vectorize(x, 16);
pass2.compute_at(output, tile_index);
pass2.vectorize(x, 8);
green_horizontal.compute_at(pass2, Var::outermost());
green_vertical.compute_at(pass2, Var::outermost());
pmn_h.compute_at(pass2, Var::outermost()).vectorize(x, 8);
pmn_v.compute_at(pass2, Var::outermost()).vectorize(x, 8);
pmn_d.compute_at(pass2, Var::outermost()).vectorize(x, 8);
green_unenhanced.compute_at(output, tile_index);
green_unenhanced.vectorize(x, 8);
d_hat_top_known.compute_at(output, tile_index);
d_hat_top_known.vectorize(x, 8);
d_hat_top_diagonal.compute_at(output, tile_index);
d_hat_top_diagonal.vectorize(x, 8);
} else {
output.reorder_storage(c, x, y).reorder(c, x, y);
output.unroll(c);
//#output.unroll(x,2).unroll(y,2);
input.compute_root();
ig_horizontal.compute_root();
ig_vertical.compute_root();
pass2.compute_root();
output.compute_root();
//pmn_h.compute_at(pass2, Var::outermost());
//pmn_v.compute_at(pass2, Var::outermost());
//pmn_d.compute_at(pass2, Var::outermost());
d_hat_top_known.compute_root();
d_hat_top_known.vectorize(x, 4);
d_hat_top_known.gpu_tile(x, y, 8, 8);
input.unroll(x, 2).unroll(y, 2);
input.vectorize(x, 4);
input.gpu_tile(x, y, 8, 8);
ig_horizontal.vectorize(x, 4);
ig_horizontal.gpu_tile(x, y, 8, 8);
ig_vertical.vectorize(y, 4);
ig_vertical.gpu_tile(x, y, 8, 8);
pass2.vectorize(x, 4);
pass2.gpu_tile(x, y, 8, 8);
output.vectorize(x, 4);
output.gpu_tile(x, y, 8, 8);
}
output.print_loop_nest();
return output;
}
};
}
RegisterGenerator<IgdDemosaic> igd_demosaic{"igd_demosaic"};