# Trying to Write on image

I was trying to edit a diagram and add a dimension line , as you see in the attached image,but I could not reach the arrows appropriate to draw the same arrow, if it's possible to do that in Latex , I have no Idea how to, could someone help me ? I am reading these links : here and here but still I don't get it how I can draw a straight line and ...

I have tried for the code so far I can not draw the arrow with two heads, it appears only one head in one end of the middle like beside which you see the letter f , I still don't know how to write the letter beside the line:

\documentclass[11pt,a4paper,twoside,openright]{report}
\usepackage{tikz}
\usetikzlibrary{calc,intersections,through,backgrounds}
\begin{document}
\begin{tikzpicture}[--, thick]
\draw  (-10,0) -- (-9,1);
\draw  (-9,1) -- (-7.5,1);
\draw  (-7.5,1) -- (-6.5,0);
\draw  (-6.5,0) -- (-5.5,-1);
\draw  (-5.5,-1)-- (-4,-1);
\draw  (-4,-1)-- (-3,0);
%dimensions
\draw  [|<->|] (-8.25,0) -- (-8.25,1);
\draw  [|<->|] (-10,-0.5) -- (-6.5,-0.5);
\begin{scope}[dash pattern=on 2pt off 3pt on 4pt off 4pt];
\draw[dashed] (-6.5pt,0pt) -- (-6.5pt,-1pt);
\end{scope}
\begin{scope}[ultra thick]
\draw [->] (-10.5,0) -- (-1.5,0);
\draw [->] (-10,-1.5) -- (-10,1.5);
\end{scope}
\end{tikzpicture}
\end{document}

• The Format is .jpg – Farzad64 Apr 5 '15 at 13:41
• I think it must be hard from within LaTeX. If you only have a few simple diagrams like the one you posted, probably you should reproduce it with one of the LaTeX graphics packages. – Bernard Apr 5 '15 at 13:46
• What is the code you're using to try and draw on the existing diagram? – darthbith Apr 5 '15 at 14:21
• Please show us how you tried to apply the strategies in one of the links you posted and explain the problem you are having applying them in this case. For example, the answers here have seemed clear to me and I've applied the ideas successfully to other cases. So it would be helpful for me to understand what exactly you are having trouble with. As has been said before, this is not a do-my-work-for-me site. People are happy to help, but you need to make an effort to learn some basics, too. – cfr Apr 5 '15 at 15:46
• You haven't posted anything you've tried. Drawing a straight line is pretty much the single simplest thing you can do with TiKZ. But you haven't given us anything: not the code to include the picture, not the straight line, not any kind of arrow. You said the problem was that you couldn't get the same kind of arrow. Post the one you've got and somebody can easily suggest a more appropriate arrow tip from arrows.meta, for example. Every task is different, of course. But, the point is: it is your task. Not ours. Don't expect this site to do everything for you. – cfr Apr 5 '15 at 17:58

This demonstrates how to add labels to lines and how to get the dashed line in the right place. Note that (6.5pt,0.5pt) is not generally the same as (6.5,0.5)! I've also simplified your path specification a bit and removed the non-working option to tikzpicture.

• midway puts the label halfway, which is wanted for the f and c.
• pos=.95 puts the label 95% of the way to the end point, which is wanted for the labels on the axes.
• left and below specify the relative position of the label with respect to the line.

## Code

\documentclass[tikz,border=10pt]{standalone}
\begin{document}
\begin{tikzpicture}[thick]
\draw  (-10,0) -- (-9,1)  -- (-7.5,1) -- (-6.5,0)  -- (-5.5,-1) -- (-4,-1) -- (-3,0);
%dimensions
\draw  [<->] (-8.25,0) -- (-8.25,1) node [midway, right] {$f$};
\draw  [<->] (-10,-0.5) -- (-6.5,-0.5) node [midway, below] {$c$};
\draw [dashed] (-6.5,0) -- (-6.5,-.75);
\begin{scope}[ultra thick]
\draw [->] (-10.5,0) -- (-1.5,0) node [pos=.95, below] {$x$};
\draw [->] (-10,-1.5) -- (-10,1.5) node [pos=.95, left] {$y$};
\end{scope}
\end{tikzpicture}
\end{document}


JPEG is a quite worse format for drawings. Therefore it is better to redraw the image. The following example uses TikZ. The function is strictly drawn using the parameters f, c, α (\fHeight, \cWidth, \alphaAngle).

\documentclass{article}
%\usepackage{graphicx}
\usepackage{tikz}
\usetikzlibrary{arrows.meta}
\usetikzlibrary{bending}
\pagestyle{empty}

\begin{document}
\setlength{\unitlength}{.5mm}
\begin{tikzpicture}[
x=\unitlength,
y=\unitlength,
>=Triangle,
]
\def\fHeight{17}
\def\cWidth{50}
\def\alphaAngle{45}
% Image as background as help for redrawing
% \node[
%   inner sep=0pt,
%   above right,
% ] at (-16.25, -20.75)
%   {\includegraphics[width=150\unitlength]{QpYZE.jpg}}
% ;

% Coordinate axes
\begin{scope}[
thick,
->,
]
\draw (-9, 0) -- (125, 0) node[below left, xshift=-.5em] {$x$};
\draw (0, -20) -- (0, 30) node[below left, yshift=-.25em] {$z$};
\end{scope}

% Function
\pgfmathsetmacro{\xf}{\fHeight * cot(\alphaAngle)}
\draw[
semithick,
]
(0, 0)
-- (\xf, \fHeight) coordinate (A)
-- (\cWidth - \xf, \fHeight) coordinate (B)
-- (\cWidth + \xf, -\fHeight)
-- (2*\cWidth - \xf, -\fHeight)
-- (2*\cWidth, 0)
;

% Annotations
\begin{scope}[
thin,
<->,
shorten <=.4pt,
]
\draw[shorten >=.3pt]
(\cWidth/2, 0) -- node[right] {$f$} ++(0, \fHeight)
;
\draw[shorten >=.2pt]
(0, -6) -- node[below] (c) {$c$} ++(\cWidth, 0)
;
\draw[shorten <=.2pt, shorten >=.2pt]
(\xf, \fHeight + 4) -- node[above] (cp) {$c_p$}
(\cWidth - \xf, \fHeight + 4)
;
(\alphaRadius, 0) arc[start angle=0, end angle=\alphaAngle]
;
\node at (\alphaAngle/2:.65*\alphaRadius) {$\alpha$};
\end{scope}

% Help lines
\draw[thin, densely dashed]
(\cWidth, 0) -- (\cWidth, 0 |- c.south)
(A) -- (A |- cp.north)
(B) -- (B |- cp.north)
;
\end{tikzpicture}
\end{document}