tkz-base : un quatrième exemple

\documentclass[]{scrartcl} 
\usepackage[utf8]{inputenc} 
\usepackage[upright]{fourier}
\usepackage[usenames,dvipsnames]{xcolor}
\usepackage{amsmath,tkz-fct}
\usepackage[frenchb]{babel}   
\definecolor{fondpaille}{cmyk}{0,0,0.1,0}
\tkzSetUpColors[background=fondpaille,text=Maroon] 

\begin{document}
  
\begin{tikzpicture}[scale=2]
 \tkzInit[xmin=0,xmax=4,ymin=-1,ymax=2]
 \tkzAxeY[label=$f(x)$]
 \tkzDefPoint(1,0){a}
 \tkzFct[id=ln,domain=0.15:4,color=blue]{log(x)}
 \tkzArea[top color=red!80,bottom color=gray!20,domain=1:2.718]
 \tkzText[style={draw},color= blue](2,-0.8){$f(x)=\ln(x)$}
 \tkzText[color= red](2.718,-0.2){$\text{e}$}  
 \tkzAxeX
 \tkzDefPoint(2.718,1){b} 
 \tkzDrawPoints(a,b)
 \tkzPointShowCoord(b)
 \tkzText[draw](3.5,0.3){$\displaystyle 
     \mathcal{A}=\int_1^{\text{e}}\ln(x) dx$}
 \tkzText(2,0.2){$\mathcal{A}$}   
\end{tikzpicture}

\end{document}