Before a macro can process any input data and produce output data, it has to declare the input and output ports so that Impresario knows which type of input data the macro expects and which output data it creates. Input and output ports are declared in the macro’s constructor with the help of the following two methods which are implemented in the macro’s base class MacroBase:

template<typename T>
bool addInput(const std::wstring& name, 
              const std::wstring& description);

template<typename T>
bool addOutput(const std::wstring& name, 
               const std::wstring& description);

Both methods have the same arguments. With the template argument of these methods you define the type of the input or output port to be created. This can be any type.

The first argument name is the port’s name. This name is displayed in Impresario as soon as the mouse cursor is hovered over the port in the process graph editor.

The second argument description is a short description of the port.

The methods return true in case the port was successfully added to the macro, falseotherwise.

Note: Internally input and output ports are appended to separate vectors so that they are indexed in the order of definition. These indices start counting from zero. This is important to remember when you have to access the ports later on for processing.

Example

In the following code the example macro for edge detection is enhanced with one input and one output port of type lti::channel8. This type is part of the LTI Lib 2 image processing library and defined in the library’s appropriate include file.

#include "cannyedge.h"
#include "ltiChannel8.h"

LtiCannyEdge::LtiCannyEdge() : MacroBase{} {
  // set up macro description
  setName(L"lti::cannyEdges");
  setCreator(L"Lars Libuda");
  setGroup(L"Image Processing");
  setDescription(L"Detects edges in a lti::channel8");
  addInput<lti::channel8>(L"Input image",
           L"8-bit grey scale image for edge detection");
  addOutput<lti::channel8>(L"Output image",
            L"8-bit grey scale image with detected edges");
  // more code to come...
}

Please continue with section Setting up macro parameters.