Several daily activities utilize complex control systems. Many of these require the users, skill and time for their representation. These systems can be modeled and represented in the form of signal flow diagrams to represent the causal relationship between their components. One method used to calculate the equivalent Transfer Function (FT) of a diagram is the Mason Formula. This requires that all paths be found, and if this does not happen, the calculated final FT is incorrect. 
The objective of this work was to describe an image processing system, which is able, from a hand drawn diagram, to obtain the final transfer function more efficiently. Where from a hand-drawn signal flow diagram, a directed graph is automatically obtained, which represents the drawing with all the direct paths and loops present. The developed tool was shown to be able to help students and professionals correctly calculate the final FT for a given diagram, following the proposed conditions.