Specify some region and align text in that space

Question

I want to use package datatool for putting different names in one specified space of one image. Here for everyone's convenience I've formed a tikzpicture instead of image. Please see this minimal code.

\begin{filecontents}{abcd.csv}
a, b, c
Niranjan, Tambe, Vikas
Sushant, Devalekar, Shankar
Pranav, Patwardhan, Sachin
\end{filecontents}

\documentclass{article}
\usepackage{datatool}
\usepackage{tikz}
\DTLloaddb{abc}{abcd.csv}

\begin{document}
\DTLforeach{abc}{\firstname=a,\surname=b,\father=c}{\begin{tikzpicture}
\draw (-3,0) node[above]{\firstname{} \father{} \surname{} \\} -- (3,0);
\end{tikzpicture}\\
}
\end{document}

If we look at the output, I've got the names above the line. Now I want to do further things, which I don't know how to do. I want every name at the center of that line. Please note that optional arguments of node like [near end] are not useful for me right now as I want to implement all of this on an .jpg image. For now let's assume that the tikz code presented is frozen and we can't change it. It is here just for the sake of convenience and to avoid uploading a file. I want something which will allow me to specify some portion of the document and apply regular LaTeX commands on it. Please suggest me how to make LaTeX apply some commands like centering or center environment "only" on the specified portion of the document.

Answer 1

I'm not sure if I understand the question. But you can set coordinates in a tikzpicture and use them later to place your text:

\begin{filecontents}{abcd.csv}
a, b, c
Niranjan, Tambe, Vikas
Sushant, Devalekar, Shankar
Pranav, Patwardhan, Sachin
\end{filecontents}

\documentclass{article}
\usepackage{datatool}
\usepackage{tikz}
\usetikzlibrary{calc}
\DTLloaddb{abc}{abcd.csv}

\begin{document}
\begin{tikzpicture}[remember picture]
\draw (-3,0)coordinate(a1)  -- (3,0)coordinate(b1);
\draw (-2,1)coordinate(a2)  -- (4,1)coordinate(b2);
\draw (-1,2)coordinate(a3)  -- (4,2)coordinate(b3);
\end{tikzpicture}

\DTLforeach{abc}{\firstname=a,\surname=b,\father=c}{%
 \begin{tikzpicture}[remember picture, overlay]
  \node[above] at ($(a\number\value{DTLrowi})!0.5!(b\number\value{DTLrowi})$)
   {\firstname{} \father{} \surname{}};
 \end{tikzpicture}}
\end{document}

You can place with tikz an (invisible) grid over the images and then use the coordinates like in my example to add the text. See e.g. Simplest way to overlay a text + rectangle label an image? and Drawing on an image with TikZ.