add static method to FrameBufferObject to read out current contents of the default frame buffer

include/ACGL/OpenGL/Objects/FrameBufferObject.hh

@@ -217,6 +217,10 @@ public:
     //! get a list of attachment locations and names that can be used to set up a ShaderProgram
     SharedLocationMappings getAttachmentLocations() const;
 
+    //! returns the current contents of the default FrameBuffer
+    //! the format of the returned TextureData will be GL_RGB, the type will be GL_UNSIGNED_INT
+    static SharedTextureData getImageData(GLsizei _width, GLsizei _height, GLint _x = 0, GLint _y = 0, GLenum _readBuffer = GL_INVALID_ENUM);
+
     // =================================================================================================== \/
     // ============================================================================================ FIELDS \/
     // =================================================================================================== \/

src/ACGL/OpenGL/Objects/FrameBufferObject.cc

@@ -204,3 +204,25 @@ SharedLocationMappings FrameBufferObject::getAttachmentLocations() const
 
     return locationMap;
 }
+
+SharedTextureData FrameBufferObject::getImageData(GLsizei _width, GLsizei _height, GLint _x, GLint _y, GLenum _readBuffer)
+{
+    GLubyte* frameBufferData = new GLubyte[_width * _height * 3];
+
+    glBindFramebuffer(GL_FRAMEBUFFER, 0);
+    if(_readBuffer != GL_INVALID_ENUM)
+        glReadBuffer(_readBuffer);
+
+    glReadPixels(_x, _y, _width, _height, GL_RGB, GL_UNSIGNED_BYTE, frameBufferData);
+
+    SharedTextureData texData = SharedTextureData(new TextureData());
+    texData->setWidth(_width);
+    texData->setHeight(_height);
+    texData->setFormat(GL_RGB);
+    texData->setType(GL_UNSIGNED_BYTE);
+    texData->setData(frameBufferData); // frameBufferData memory will be managed by texData
+
+    openGLRareError();
+
+    return texData;
+}