Color radar image using a color table

scwx-qt/gl/radar.frag

@@ -3,7 +3,7 @@
 // Lower the default precision to medium
 precision mediump float;
 
-uniform sampler2D uTexture;
+uniform sampler1D uTexture;
 
 flat in uint dataMoment;
 
@@ -11,16 +11,7 @@ layout (location = 0) out vec4 fragColor;
 
 void main()
 {
-   if (dataMoment < 126u)
+   float texCoord = float(dataMoment - 2u) / 253.0f; // TODO: Scale properly
-   {
+
-      fragColor = vec4(0.0f, 0.5f, 0.0f, 0.9f);
+   fragColor = texture(uTexture, texCoord);
-   }
-   else if (dataMoment < 156u)
-   {
-      fragColor = vec4(1.0f, 0.75f, 0.0f, 0.9f);
-   }
-   else
-   {
-      fragColor = vec4(1.0f, 0.0f, 0.0f, 0.9f);
-   }
 }

scwx-qt/source/scwx/qt/map/map_widget.cpp

@@ -106,6 +106,14 @@ void MapWidget::AddLayers()
 
    radarView->Initialize();
 
+   QString colorTableFile = qgetenv("COLOR_TABLE");
+   if (!colorTableFile.isEmpty())
+   {
+      std::shared_ptr<common::ColorTable> colorTable =
+         common::ColorTable::Load(colorTableFile.toUtf8().constData());
+      radarView->LoadColorTable(colorTable);
+   }
+
    // QMapboxGL::addCustomLayer will take ownership of the QScopedPointer
    QScopedPointer<QMapbox::CustomLayerHostInterface> pHost(
       new RadarLayer(radarView, p->gl_));

scwx-qt/source/scwx/qt/map/radar_layer.cpp

@@ -36,6 +36,7 @@ public:
        uMapScreenCoordLocation_(GL_INVALID_INDEX),
        vbo_ {GL_INVALID_INDEX},
        vao_ {GL_INVALID_INDEX},
+       texture_ {GL_INVALID_INDEX},
        numVertices_ {0}
    {
    }
@@ -49,6 +50,7 @@ public:
    GLint                 uMapScreenCoordLocation_;
    std::array<GLuint, 2> vbo_;
    GLuint                vao_;
+   GLuint                texture_;
 
    GLsizeiptr numVertices_;
 };
@@ -143,6 +145,11 @@ void RadarLayer::initialize()
    gl.glEnableVertexAttribArray(1);
 
    p->numVertices_ = vertices.size() / 2;
+
+   // Create color table
+   gl.glGenTextures(1, &p->texture_);
+   UpdateColorTable();
+   gl.glTexParameteri(GL_TEXTURE_1D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
 }
 
 void RadarLayer::render(const QMapbox::CustomLayerRenderParameters& params)
@@ -170,6 +177,8 @@ void RadarLayer::render(const QMapbox::CustomLayerRenderParameters& params)
    gl.glUniformMatrix4fv(
       p->uMVPMatrixLocation_, 1, GL_FALSE, glm::value_ptr(uMVPMatrix));
 
+   gl.glActiveTexture(GL_TEXTURE0);
+   gl.glBindTexture(GL_TEXTURE_1D, p->texture_);
    gl.glBindVertexArray(p->vao_);
    gl.glDrawArrays(GL_TRIANGLES, 0, p->numVertices_);
 }
@@ -186,6 +195,27 @@ void RadarLayer::deinitialize()
    p->uMVPMatrixLocation_ = GL_INVALID_INDEX;
    p->vao_                = GL_INVALID_INDEX;
    p->vbo_                = {GL_INVALID_INDEX};
+   p->texture_            = GL_INVALID_INDEX;
+}
+
+void RadarLayer::UpdateColorTable()
+{
+   OpenGLFunctions& gl = p->gl_;
+
+   const std::vector<boost::gil::rgba8_pixel_t>& colorTable =
+      p->radarView_->color_table();
+
+   gl.glActiveTexture(GL_TEXTURE0);
+   gl.glBindTexture(GL_TEXTURE_1D, p->texture_);
+   gl.glTexImage1D(GL_TEXTURE_1D,
+                   0,
+                   GL_RGBA,
+                   (GLsizei) colorTable.size(),
+                   0,
+                   GL_RGBA,
+                   GL_UNSIGNED_BYTE,
+                   colorTable.data());
+   gl.glGenerateMipmap(GL_TEXTURE_1D);
 }
 
 static glm::vec2

scwx-qt/source/scwx/qt/map/radar_layer.hpp

@@ -28,6 +28,8 @@ public:
    void render(const QMapbox::CustomLayerRenderParameters&) override final;
    void deinitialize() override final;
 
+   void UpdateColorTable();
+
 private:
    std::unique_ptr<RadarLayerImpl> p;
 };

scwx-qt/source/scwx/qt/view/radar_view.cpp

@@ -2,6 +2,7 @@
 #include <scwx/common/constants.hpp>
 
 #include <boost/log/trivial.hpp>
+#include <boost/range/irange.hpp>
 #include <boost/timer/timer.hpp>
 
 namespace scwx
@@ -21,7 +22,11 @@ class RadarViewImpl
 public:
    explicit RadarViewImpl(std::shared_ptr<manager::RadarManager> radarManager,
                           std::shared_ptr<QMapboxGL>             map) :
-       radarManager_(radarManager), map_(map)
+       radarManager_(radarManager),
+       map_(map),
+       colorTable_ {boost::gil::rgba8_pixel_t(0, 128, 0, 255),
+                    boost::gil::rgba8_pixel_t(255, 192, 0, 255),
+                    boost::gil::rgba8_pixel_t(255, 0, 0, 255)}
    {
    }
    ~RadarViewImpl() = default;
@@ -32,6 +37,8 @@ public:
    std::vector<float>    vertices_;
    std::vector<uint8_t>  dataMoments8_;
    std::vector<uint16_t> dataMoments16_;
+
+   std::vector<boost::gil::rgba8_pixel_t> colorTable_;
 };
 
 RadarView::RadarView(std::shared_ptr<manager::RadarManager> radarManager,
@@ -69,6 +76,11 @@ const std::vector<float>& RadarView::vertices() const
    return p->vertices_;
 }
 
+const std::vector<boost::gil::rgba8_pixel_t>& RadarView::color_table() const
+{
+   return p->colorTable_;
+}
+
 void RadarView::Initialize()
 {
    BOOST_LOG_TRIVIAL(debug) << logPrefix_ << "Initialize()";
@@ -297,6 +309,26 @@ void RadarView::Initialize()
       << logPrefix_ << "Vertices calculated in " << timer.format(6, "%ws");
 }
 
+void RadarView::LoadColorTable(std::shared_ptr<common::ColorTable> colorTable)
+{
+   // TODO: Make size, offset and scale dynamic
+   const float offset = 66.0f;
+   const float scale  = 2.0f;
+
+   std::vector<boost::gil::rgba8_pixel_t>& lut = p->colorTable_;
+   lut.resize(254);
+
+   auto dataRange = boost::irange<uint16_t>(2, 255);
+
+   std::for_each(std::execution::par_unseq,
+                 dataRange.begin(),
+                 dataRange.end(),
+                 [&](uint16_t i) {
+                    float f                     = (i - offset) / scale;
+                    lut[i - *dataRange.begin()] = colorTable->Color(f);
+                 });
+}
+
 } // namespace view
 } // namespace qt
 } // namespace scwx

scwx-qt/source/scwx/qt/view/radar_view.hpp

@@ -1,5 +1,6 @@
 #pragma once
 
+#include <scwx/common/color_table.hpp>
 #include <scwx/qt/manager/radar_manager.hpp>
 
 #include <memory>
@@ -35,7 +36,10 @@ public:
    const std::vector<uint16_t>& data_moments16() const;
    const std::vector<float>&    vertices() const;
 
+   const std::vector<boost::gil::rgba8_pixel_t>& color_table() const;
+
    void Initialize();
+   void LoadColorTable(std::shared_ptr<common::ColorTable> colorTable);
 
 private:
    std::unique_ptr<RadarViewImpl> p;