add convertTextureData function

include/ACGL/OpenGL/Data/TextureData.hh

@@ -143,6 +143,11 @@ private:
 
 ACGL_SMARTPOINTER_TYPEDEFS(TextureData)
 
+//! Converts the texture data in _from to the target format and type given in
+//! _to. Overwrites width, height, and depth in _to. Old texture data is removed
+//! and new memory is allocated.
+void convertTextureData(const SharedTextureData& _from, const SharedTextureData& _to);
+
 } // OpenGL
 } // ACGL
 

src/ACGL/OpenGL/Data/TextureData.cc

@@ -7,8 +7,8 @@
 #include <ACGL/OpenGL/Data/TextureData.hh>
 #include <ACGL/Utils/Memory.hh>
 
-using namespace ACGL;
-using namespace ACGL::OpenGL;
+namespace ACGL {
+namespace OpenGL {
 
 GLsizei  TextureData::getPackAlignment() const
 {
@@ -304,3 +304,74 @@ void TextureData::setTexel( glm::uvec2 _texCoord, glm::vec4 _color )
     }
 }
 
+float grayscaleMixdown(float _r, float _g, float _b)
+{
+    return 0.299f * _r + 0.587f * _g + 0.114f * _b;
+}
+
+glm::vec4 convertTexelNumChannels(glm::vec4 _texel, GLsizei _from, GLsizei _to)
+{
+    if (_from == _to) {
+        return _texel;
+    }
+    else if (_from == 1) {
+        switch (_to) {
+            case 2: return {_texel.r, 1.0, 0.0, 0.0};
+            case 3: return {_texel.r, _texel.r, _texel.r, 0.0};
+            case 4: return {_texel.r, _texel.r, _texel.r, 1.0};
+        }
+    }
+    else if (_from == 2) {
+        switch (_to) {
+            case 1: return {_texel.r, 0.0, 0.0, 0.0};
+            case 3: return {_texel.r, _texel.r, _texel.r, _texel.g};
+            case 4: return {_texel.r, _texel.r, _texel.r, _texel.g};
+        }
+    }
+    else if (_from == 3) {
+        switch (_to) {
+            case 1: return {grayscaleMixdown(_texel.r, _texel.g, _texel.b), 0.0, 0.0, 0.0};
+            case 2: return {grayscaleMixdown(_texel.r, _texel.g, _texel.b), 1.0, 0.0, 0.0};
+            case 4: return {_texel.r, _texel.r, _texel.r, 1.0};
+        }
+    }
+    else if (_from == 4) {
+        switch (_to) {
+            case 1: return {grayscaleMixdown(_texel.r, _texel.g, _texel.b), 0.0, 0.0, 0.0};
+            case 2: return {grayscaleMixdown(_texel.r, _texel.g, _texel.b), 1.0, 0.0, 0.0};
+            case 3: return {_texel.r, _texel.r, _texel.r, 0.0};
+        }
+    }
+    return _texel;
+}
+
+void convertTextureData(const SharedTextureData& _from, const SharedTextureData& _to)
+{
+    assert(_from);
+    assert(_to);
+    if (!_from->getData()) {
+        ACGL::Utils::error() << "Cannot convert TextureData: source TextureData contains no data" << std::endl;
+        return;
+    }
+
+    // Setup target texture dimensions
+    _to->setWidth(_from->getWidth());
+    _to->setHeight(_from->getHeight());
+    _to->setDepth(_from->getDepth());
+
+    // Allocate new memory
+    _to->deleteData();
+    GLubyte* data = new GLubyte[_to->getSizeInBytes()];
+    _to->setData(data);
+
+    // Transfer pixels
+    for (GLsizei y = 0; y < _to->getHeight(); ++y) {
+        for (GLsizei x = 0; x < _to->getWidth(); ++x) {
+            auto texel = convertTexelNumChannels(_from->getTexel({x, y}), _from->getNumberOfChannels(), _to->getNumberOfChannels());
+            _to->setTexel({x, y}, texel);
+        }
+    }
+}
+
+} // namespace OpenGL
+} // namespace ACGL