Add LookupTable class

#470

library/phx/resources/types/lookup_table.cpp

+//------------------------------------------------------------------------------
+// Project Phoenix
+//
+// Copyright (c) 2017-2018 RWTH Aachen University, Germany,
+// Virtual Reality & Immersive Visualization Group.
+//------------------------------------------------------------------------------
+//                                 License
+//
+// Licensed under the 3-Clause BSD License (the "License");
+// you may not use this file except in compliance with the License.
+// See the file LICENSE for the full text.
+// You may obtain a copy of the License at
+//
+//     https://opensource.org/licenses/BSD-3-Clause
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//------------------------------------------------------------------------------
+
+#include "phx/resources/types/lookup_table.hpp"
+
+#include <memory>
+
+namespace phx {
+LookupTable::LookupTable(const TransferFunction& transfer_function,
+                         int num_colors)
+    : min_key_(transfer_function.GetEntries().front().scalar),
+      max_key_(transfer_function.GetEntries().back().scalar),
+      transfer_function_(transfer_function) {
+  Generate(num_colors);
+}
+
+void LookupTable::Generate(int num_colors) {
+  float step = (max_key_ - min_key_) / (num_colors - 1);
+  for (auto i = 0; i < num_colors; ++i) {
+    lookup_table_.push_back(
+        transfer_function_.Interpolate(min_key_ + i * step));
+  }
+}
+glm::vec4 LookupTable::GetColor(int index) const {
+  return lookup_table_.at(index);
+}
+
+std::size_t LookupTable::GetIndex(float key) const {
+  return static_cast<std::size_t>(
+      std::round((GetSize() - 1) * ((key - min_key_) / (max_key_ - min_key_))));
+}
+
+std::size_t LookupTable::GetSize() const { return lookup_table_.size(); }
+
+std::unique_ptr<gl::texture_1d> LookupTable::GetTexture1D() const {
+  auto lookup_texture = std::make_unique<gl::texture_1d>();
+  lookup_texture->set_storage(0, GL_RGBA,
+                              static_cast<GLsizei>(lookup_table_.size()));
+  lookup_texture->set_sub_image(0, 0,
+                                static_cast<GLsizei>(lookup_table_.size()),
+                                GL_RGBA8, GL_FLOAT, lookup_table_.data());
+  return lookup_texture;
+}
+
+}  // namespace phx

library/phx/resources/types/lookup_table.hpp

+//------------------------------------------------------------------------------
+// Project Phoenix
+//
+// Copyright (c) 2017-2018 RWTH Aachen University, Germany,
+// Virtual Reality & Immersive Visualization Group.
+//------------------------------------------------------------------------------
+//                                 License
+//
+// Licensed under the 3-Clause BSD License (the "License");
+// you may not use this file except in compliance with the License.
+// See the file LICENSE for the full text.
+// You may obtain a copy of the License at
+//
+//     https://opensource.org/licenses/BSD-3-Clause
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//------------------------------------------------------------------------------
+
+#ifndef LIBRARY_PHX_RESOURCES_TYPES_LOOKUP_TABLE_HPP_
+#define LIBRARY_PHX_RESOURCES_TYPES_LOOKUP_TABLE_HPP_
+
+#include <memory>
+#include <vector>
+
+#include "phx/resources/types/shader_source.hpp"
+#include "phx/resources/types/transfer_function.hpp"
+#include "phx/suppress_warnings.hpp"
+
+SUPPRESS_WARNINGS_BEGIN
+#include "gl/texture.hpp"
+#include "glm/detail/type_vec4.hpp"
+SUPPRESS_WARNINGS_END
+
+namespace phx {
+
+class PHOENIX_EXPORT LookupTable {
+ public:
+  LookupTable(const TransferFunction& transfer_function, int num_colors);
+  LookupTable(const LookupTable&) = default;
+  LookupTable(LookupTable&&) = default;
+  ~LookupTable() = default;
+
+  std::size_t GetIndex(float key) const;
+  glm::vec4 GetColor(int index) const;
+  std::size_t GetSize() const;
+
+  std::unique_ptr<gl::texture_1d> GetTexture1D() const;
+
+ private:
+  void Generate(int num_colors);
+
+  float min_key_;
+  float max_key_;
+  std::vector<glm::vec4> lookup_table_;
+  const TransferFunction transfer_function_;
+};
+}  // namespace phx
+
+#endif  // LIBRARY_PHX_RESOURCES_TYPES_LOOKUP_TABLE_HPP_

tests/src/test_lookup_table.cpp

+//------------------------------------------------------------------------------
+// Project Phoenix
+//
+// Copyright (c) 2017-2018 RWTH Aachen University, Germany,
+// Virtual Reality & Immersive Visualization Group.
+//------------------------------------------------------------------------------
+//                                 License
+//
+// Licensed under the 3-Clause BSD License (the "License");
+// you may not use this file except in compliance with the License.
+// See the file LICENSE for the full text.
+// You may obtain a copy of the License at
+//
+//     https://opensource.org/licenses/BSD-3-Clause
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//------------------------------------------------------------------------------
+
+#include "phx/resources/types/lookup_table.hpp"
+#include "phx/resources/types/transfer_function.hpp"
+
+#include "catch/catch.hpp"
+
+SCENARIO("Creating and accesing a Lookup Table", "[phx][phx::LookupTable]") {
+  GIVEN("A test transfer function") {
+    phx::TransferFunction transfer_function;
+    glm::vec4 red_color{1.0f, 0.0f, 0.0f, 0.0f};
+    glm::vec4 black_color{0.0f, 0.0f, 0.0f, 0.0f};
+    transfer_function.SetEntries({{0.0f, red_color}, {1.0f, black_color}});
+
+    WHEN("We create Lookup Table from the given Transfer function") {
+      phx::LookupTable lut(transfer_function, 11);
+
+      THEN("The Lookup Table is generated correctly") {
+        REQUIRE(lut.GetColor(0) == red_color);
+        REQUIRE(lut.GetColor(2) == glm::vec4(0.8f, 0.0f, 0.0f, 0.0f));
+        REQUIRE(lut.GetColor(5) == glm::vec4(0.5f, 0.0f, 0.0f, 0.0f));
+        REQUIRE(lut.GetColor(7) == glm::vec4(0.3f, 0.0f, 0.0f, 0.0f));
+        REQUIRE(lut.GetColor(10) == black_color);
+      }
+
+      THEN("Keys can be converted indices") {
+        REQUIRE(lut.GetIndex(0.0f) == 0);
+        REQUIRE(lut.GetIndex(1.0f) == 10);
+        REQUIRE(lut.GetIndex(0.56f) == 6);
+      }
+    }
+
+    WHEN("We ask for a nearest neighbor interpolated Lookup Table") {
+      transfer_function.SetMode(
+          phx::TransferFunction::InterpolationMode::NEAREST_NEIGHBOR);
+      phx::LookupTable lut(transfer_function, 11);
+      THEN("The Lookuptable is generated correctly") {
+        REQUIRE(lut.GetColor(0) == red_color);
+        REQUIRE(lut.GetColor(2) == red_color);
+        REQUIRE(lut.GetColor(5) == black_color);
+        REQUIRE(lut.GetColor(7) == black_color);
+        REQUIRE(lut.GetColor(10) == black_color);
+      }
+    }
+  }
+}