root/apps/glsl/halide_ycc_glsl_generator.cpp

DEFINITIONS

1. build

#include "Halide.h"

namespace {

class RgbToYcc : public Halide::Generator<RgbToYcc> {
public:
    ImageParam input8{UInt(8), 3, "input8"};
    Func build() {
        assert(get_target().has_feature(Target::OpenGL));
        Func out("out");
        Var x("x"), y("y"), c("c");

        // The algorithm
        Func input("input");
        input(x, y, c) = cast<float>(input8(x, y, c)) / 255.0f;

        Func Y("Y"), Cb("Cb"), Cr("Cr");
        Y(x,y) = 16.f/255.f + (0.257f * input(x, y, 0) +
                               0.504f * input(x, y, 1) +
                               0.098f * input(x, y, 2));
        Cb(x,y) = 128.f/255.f + (0.439f * input(x, y, 0) +
                                 -0.368f * input(x, y, 1) +
                                 -0.071f * input(x, y, 2));
        Cr(x,y) = 128.f/255.f + (-0.148f * input(x, y, 0) +
                                 -0.291f * input(x, y, 1) +
                                 0.439f * input(x, y, 2));
        out(x, y, c) = cast<uint8_t>(select(c == 0, Y(x,y),
                                            c == 1, Cb(x,y),
                                            c == 2, Cr(x,y),
                                            0.0f) * 255.f);

        // Schedule for GLSL
        input8.dim(2).set_bounds(0, 3);
        out.bound(c, 0, 3);
        out.glsl(x, y, c);

        return out;
    }
};

Halide::RegisterGenerator<RgbToYcc> register_me{"halide_ycc_glsl"};

}  // namespace