Write interpolator class (but dont integrate it)

src/interpolator.cpp

@@ -0,0 +1,90 @@
+/*  Python-rgbcx Texture Compression Library
+    Copyright (C) 2021 Andrew Cassidy <drewcassidy@me.com>
+    Partially derived from rgbcx.h written by Richard Geldreich <richgel99@gmail.com>
+    and licenced under the public domain
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Affero General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU Affero General Public License for more details.
+
+    You should have received a copy of the GNU Affero General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "interpolator.h"
+
+#include <cassert>
+
+// region InterpolatorIdeal implementation
+int rgbcx::InterpolatorIdeal::Interpolate5(int v0, int v1) { return Interpolate5or6(v0, v1); }
+int rgbcx::InterpolatorIdeal::Interpolate6(int v0, int v1) { return Interpolate5or6(v0, v1); }
+int rgbcx::InterpolatorIdeal::InterpolateHalf5(int v0, int v1) { return InterpolateHalf5or6(v0, v1); }
+int rgbcx::InterpolatorIdeal::InterpolateHalf6(int v0, int v1) { return InterpolateHalf5or6(v0, v1); }
+
+int rgbcx::InterpolatorIdeal::Interpolate5or6(int v0, int v1) {
+    assert(v0 < 256 && v1 < 256);
+    return (v0 * 2 + v1) / 3;
+}
+
+int rgbcx::InterpolatorIdeal::InterpolateHalf5or6(int v0, int v1) {
+    assert(v0 < 256 && v1 < 256);
+    return (v0 + v1) / 2;
+}
+// endregion
+
+// region InterpolatorIdealRound implementation
+int rgbcx::InterpolatorIdealRound::Interpolate5(int v0, int v1) { return Interpolate5or6Round(v0, v1); }
+int rgbcx::InterpolatorIdealRound::Interpolate6(int v0, int v1) { return Interpolate5or6Round(v0, v1); }
+
+int rgbcx::InterpolatorIdealRound::Interpolate5or6Round(int v0, int v1) {
+    assert(v0 < 256 && v1 < 256);
+    return (v0 * 2 + v1 + 1) / 3;
+}
+// endregion
+
+// region InterpolatorNvidia implementation
+int rgbcx::InterpolatorNvidia::Interpolate5(int v0, int v1) {
+    assert(v0 < 32 && v1 < 32);
+    return ((2 * v0 + v1) * 22) / 8;
+}
+
+int rgbcx::InterpolatorNvidia::Interpolate6(int v0, int v1) {
+    assert(v0 < 256 && v1 < 256);
+    const int gdiff = v1 - v0;
+    return (256 * v0 + (gdiff / 4) + 128 + gdiff * 80) / 256;
+}
+
+int rgbcx::InterpolatorNvidia::InterpolateHalf5(int v0, int v1) {
+    assert(v0 < 32 && v1 < 32);
+    return ((v0 + v1) * 33) / 8;
+}
+
+int rgbcx::InterpolatorNvidia::InterpolateHalf6(int v0, int v1) {
+    assert(v0 < 256 && v1 < 256);
+    const int gdiff = v1 - v0;
+    return (256 * v0 + gdiff / 4 + 128 + gdiff * 128) / 256;
+}
+// endregion
+
+// region InterpolatorAMD implementation
+int rgbcx::InterpolatorAMD::Interpolate5(int v0, int v1) { return Interpolate5or6(v0, v1); }
+int rgbcx::InterpolatorAMD::Interpolate6(int v0, int v1) { return Interpolate5or6(v0, v1); }
+int rgbcx::InterpolatorAMD::InterpolateHalf5(int v0, int v1) { return InterpolateHalf5or6(v0, v1); }
+int rgbcx::InterpolatorAMD::InterpolateHalf6(int v0, int v1) { return InterpolateHalf5or6(v0, v1); }
+
+int rgbcx::InterpolatorAMD::Interpolate5or6(int v0, int v1) {
+    assert(v0 < 256 && v1 < 256);
+    return (v0 * 43 + v1 * 21 + 32) >> 6;
+}
+
+int rgbcx::InterpolatorAMD::InterpolateHalf5or6(int v0, int v1) {
+    assert(v0 < 256 && v1 < 256);
+    return (v0 + v1 + 1) >> 1;
+}
+// endregion

src/interpolator.h

@@ -0,0 +1,73 @@
+/*  Python-rgbcx Texture Compression Library
+    Copyright (C) 2021 Andrew Cassidy <drewcassidy@me.com>
+    Partially derived from rgbcx.h written by Richard Geldreich <richgel99@gmail.com>
+    and licenced under the public domain
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Affero General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU Affero General Public License for more details.
+
+    You should have received a copy of the GNU Affero General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+namespace rgbcx {
+
+class Interpolator {
+   public:
+    virtual int Interpolate5(int v0, int v1) = 0;
+    virtual int Interpolate6(int v0, int v1) = 0;
+    virtual int InterpolateHalf5(int v0, int v1) = 0;
+    virtual int InterpolateHalf6(int v0, int v1) = 0;
+    virtual ~Interpolator() noexcept = default;
+};
+
+class InterpolatorIdeal : public Interpolator {
+   public:
+    virtual int Interpolate5(int v0, int v1);
+    virtual int Interpolate6(int v0, int v1);
+    virtual int InterpolateHalf5(int v0, int v1);
+    virtual int InterpolateHalf6(int v0, int v1);
+
+   private:
+    int Interpolate5or6(int v0, int v1);
+    int InterpolateHalf5or6(int v0, int v1);
+};
+
+class InterpolatorIdealRound : public InterpolatorIdeal {
+   public:
+    virtual int Interpolate5(int v0, int v1);
+    virtual int Interpolate6(int v0, int v1);
+
+   private:
+    int Interpolate5or6Round(int v0, int v1);
+};
+
+class InterpolatorNvidia : public Interpolator {
+   public:
+    virtual int Interpolate5(int v0, int v1);
+    virtual int Interpolate6(int v0, int v1);
+    virtual int InterpolateHalf5(int v0, int v1);
+    virtual int InterpolateHalf6(int v0, int v1);
+};
+
+class InterpolatorAMD : public Interpolator {
+   public:
+    virtual int Interpolate5(int v0, int v1);
+    virtual int Interpolate6(int v0, int v1);
+    virtual int InterpolateHalf5(int v0, int v1);
+    virtual int InterpolateHalf6(int v0, int v1);
+
+   private:
+    int Interpolate5or6(int v0, int v1);
+    int InterpolateHalf5or6(int v0, int v1);
+};
+}  // namespace rgbcx