#390 Protractor image using tikz package in LaTeX

I converted pdf to png using program ImageMagick with the following parameters:

bat script:

magick -density 400 -quality 100 -colorspace sRGB ex390.pdf ex390.png

LaTeX script:

\documentclass{standalone}
\usepackage{tikz}
\usepackage{ifthen}
\usepackage{intcalc}
\begin{document}
	\begin{tikzpicture}
		\draw (6,0) arc [radius=6, start angle=0, end angle=180] -- (-6,-0.5) -- (6,-0.5) -- cycle;
		\foreach \i in {0,10,...,180}{
			\draw[red] (\i:5.2) -- (\i:6);
			\node[red, rotate=-90+\i] at (\i:5) {\i};
			\node[rotate=90-\i] at (180-\i:4.5) {\i};
			\draw (\i:1) -- (\i:3);
		}
		\foreach \i in {0,1,...,180}{
			\ifthenelse{\intcalcMod{\i}{10}=0}{
				}{
				\ifthenelse{\intcalcMod{\i}{10}=5}{
					\draw[blue] (\i:5.4) -- (\i:6);
				}{
					\draw (\i:5.6) -- (\i:6);
				}	
			}
		}
		\draw[->, line width=1] (0,0) -- (4,0);
		\draw[->, line width=1] (0,0) -- (0,4);
		\draw[->, line width=1] (0,0) -- (-4,0);
		\filldraw[fill=white] (0,0) circle [radius=0.2] node {+};
	\end{tikzpicture}
\end{document}