The version of imagemagick should be later than 7.1.1.26 because OffIfOpaque AlphaChannelOption is available after this version. Otherwise may cause compile failures.
For now, the best I can do is update the build.rs to require 7.1.1 (adding -26 or .26 doesn't work) and update the README file. Thanks for letting me know. Fixed in commit d50f01b
The version of imagemagick should be later than 7.1.1.26 because
OffIfOpaque
AlphaChannelOption is available after this version. Otherwise may cause compile failures.https://github.com/nlfiedler/magick-rust/blob/master/src/types/alpha_channel_option.rs#L37