[Tex/LaTex] Center a text above and under an arrow in a tikz picture

tikz-arrowstikz-pgf

I am trying to draw a flow diagram and I am having some trouble getting the details right. For now, my code looks like this:

% Define block styles
\tikzstyle{block} = [rectangle, draw, fill=red!40, 
    text width=6em, text centered, rounded corners, minimum height=3em]
\tikzstyle{arrow} = [draw, -latex']

\begin{figure}[!h]
\centering
\begin{tikzpicture}[node distance = 5cm, auto]
    % Place nodes
    \draw ++(0,0) node [block] (signal) {Señal temporal};
    \draw ++(4,0) node [block] (FFT)  {Transformada rápida de Fourier};
    \draw ++(9,0) node [block] (MSF)  {Mapeo a escala de Mel};
    \draw ++(13.5,-1.5) node [block] (Log)  {Logaritmo de la potencia};
    \draw ++(9,-3) node [block] (DCT) {Transformada Coseno Discreta};
    \draw ++(4,-3) node [block] (MFCC) {Descriptores MFCC};

    % Draw edges
    \path [arrow] (signal) -- (FFT);
    \path [arrow] (FFT) -- node {espectro} (MSF) ;
    \draw[arrow] (MSF.east) -- node [above] {espectro} node [below] {de Mel} ++(1.5,0)   -|  (Log.north);    
    \draw[arrow] (Log.south) --  ++(0,-0.86)   --  (DCT.east);    
    \path [arrow] (DCT) -- (MFCC) ;
    
   
\end{tikzpicture}
\caption[MFCC]{Diagrama en bloques del cálculo de las MFCC para un frame.}
\label{MFCC}
\end{figure}

Which outputs this:

How my tikz picture looks like

In the first line, all the way up to the right there is a text above and under the arrow "espectro de Mel" I would like this to be centered to the right like this:

What I would like to accomplish

Of course, I can accomplish this easily with an image editor but I think this can by done with code.

Thank you for your answers, and I will gladly receive any suggestions regarding the rest of the image as well.

Best Answer

Some comments:

  • tikzset{stylename/.style={}} is recommended over \tikzstyle.
  • Nodes are positioned relative to each other, using the syntax of the positioning library.

  • The right-down line is drawn with (node1) -| (node2), and in this case pos=0.25 will be halfway between the first node and the corner.

    In your original code you have (MSF.east) -- <nodes are here> ++(1.5,0) -| (Log.north), so the nodes are placed halfway between the right edge of MSF and a point 1.5 units right of MSF. Then the line continues horizontally until it reaches the x-coordinate of Log.north, where it turns and goes down to Log.

  • While it still works, the arrows library is deprecated in favour of arrows.meta. Making that switch requires a small change in the specification of the arrow tip.

enter image description here

\documentclass[12pt]{article}
\usepackage[utf8]{inputenc}
\usepackage{tikz}
\tikzset{
     block/.style={rectangle, draw, fill=red!40, text width=6em,
                   text centered, rounded corners, minimum height=3em},
     arrow/.style={-{Stealth[]}}
     }
\usetikzlibrary{positioning,arrows.meta}
\begin{document}
\begin{tikzpicture}
    \node [block] (signal) {Señal temporal};
    \node [block,right=of signal] (FFT)  {Transformada rápida de Fourier};
    \node [block,right=2cm of FFT] (MSF)  {Mapeo a escala de Mel};
    \node [block,below right=0.2cm and 1cm of MSF] (Log)  {Logaritmo de la potencia};
    \node [block,below left=0.2cm and 1cm of Log] (DCT) {Transformada Coseno Discreta};
    \node [block,left=2cm of DCT] (MFCC) {Descriptores MFCC};


    % Draw edges
    \draw [arrow] (signal) -- (FFT);
    \draw [arrow] (FFT) -- node [above] {espectro} (MSF);
    \draw[arrow] (MSF)  -|  (Log) node [above,pos=0.25] {espectro} node [below,pos=0.25] {de Mel}   ;  
    \draw[arrow] (Log.south) |-  (DCT.east);  
    \draw [arrow] (DCT) -- (MFCC) ;
\end{tikzpicture}
\end{document}
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