I used libtiff in Delphi before and I want to port this app to Mac with Lazarus. Does someone know how to build the libtiff directly from the c source (http://www.libtiff.org/) and use it in Lazarus?
Jus
You have a number of options. If libtiff is all you need, you can download the source archive, extract it and build it with the usual unix chain of build commands, i.e. "./configure", "make" and "sudo make install". For further informations check for the files README and INSTALL. libtiff is quite a straight forward thing. You may have to pass the path to the library to the linker.
The other option is using a package manager, ie. fink, macports or homebrew. If you are going to use other tools and C libraries, i would recommend to use one of them, because they check for dependencies, apply patches as needed by some of the trickier packages and provide clean uninstalls. However, they cannot be mixed and used at the same time. My personal preference is fink and i maintain the fpc and lazarus packages, but as long as it comes to simple packages like libtiff, all of them do a pretty good job.
Michael Schindler