failure

$ convert -density 300 example.eps example.png
convert-im6.q16: not authorized `example.eps’ @ error/constitute.c/ReadImage/412.
convert-im6.q16: no images defined `example.png’ @ error/convert.c/ConvertImageCommand/3258.

Just edit the file /etc/ImageMagick-6/policy.xml and modify

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<policy domain="coder" rights="none" pattern="PS" />
<policy domain="coder" rights="none" pattern="EPI" />
<policy domain="coder" rights="none" pattern="PDF" />
<policy domain="coder" rights="none" pattern="XPS" />

to

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<policy domain="coder" rights="read|write" pattern="PDF,PS" />
example.png

example.png


Reference

[1] https://askubuntu.com/questions/1081895/trouble-with-batch-conversion-of-png-to-pdf-using-convert