A simple way to detect imagemagick converter, avoid to use magick package(issue #85)
Using magick by default. We can use magick in any OS with imagemagick version > 7.0
When the program cannot find magick, then it will try to find convert (imagemagick version < 7.0)
2.1 if program find convert, then it will use convert in lieu of magick
2.2 if program cannot find convert, the program will stop runnig and report the error message.
A simple way to detect imagemagick converter, avoid to use magick package(issue #85)