Solved by refering to the link:
https://issues.sonatype.org/browse/MVNCENTRAL-463
candrews Craig Andrews added a comment - 06/16/14 07:30 PM
https://jira.codehaus.org/browse/MAVENUPLOAD-2350 explains that com.jhlabs:imaging was renamed to com.jhlabs:filters, and that is in
Maven Central.
So I suppose everyone could exclude the com.jhlabs:imaging from jcaptcha and depend on com.jhlabs:filters:2.0.235-1 instead.
Of course, it would be better if someone would upload a new version of com.octo.captcha:jcaptcha with that dependency changed.