Strange lines in a shade of the object

Question

I'm trying to depict a sphere with shading

\documentclass[tikz]{standalone}

\usepackage{tikz}
\usepackage{pgfplots}
\pgfplotsset{compat=newest}

\begin{document}
    \begin{tikzpicture}[scale = 2.5]
        \def\spradius{1}
        % draws a shaded sphere
        \shade[ball color = lightgray, opacity = 0.5] (0,0,0) circle (\spradius cm);
    \end{tikzpicture}
\end{document}

After compiling I have a next pdf image

But then I run a convert to png

magick convert -density 600 -depth 24 -quality 100 .pdf .png

on this pdf and get

So those black lines become apparent.

What am I doing wrong?

It seems to be dependent of the resolution, try a much much higher density and then resample it down later — daleif, Jan 29 '20 at 12:39
I've used a resample -600, but the lines are there - you can see them in zoomin. Is it some layer in pdf that should be ignored? — dEmigOd, Jan 29 '20 at 12:53
Can you check whether the addendum in this post allows you to solve the problem? — , Jan 29 '20 at 15:14
No problem with a direct convertion to PNG with PDF-XChange. — vi pa, Jan 29 '20 at 19:37

score 1 · Answer 1 · answered Jun 26 '21 at 16:55

The point is the installed version of Ghostscript: Magick uses Ghostscript to convert PDF files into raster images. In some versions, shaded balls have this issue.

A possible solution is installing a newer version of Ghostscript before converting the PDFs. I had the same issue with Ghostscript v9.26, but after installing v9.54 (the most recent stable release at the time of writing) the lines disappeared.

I've used the following string to convert both images:

convert -density 600 -depth 24 -quality 100 .pdf .png

Strange lines in a shade of the object

1 Answers1