Dear R Community, I'm working on an R package that needs resizing of images. I try to keep dependencies of Tcl packages as little as possible, so I implemented the Image Scaling procedure in C as a Tcl extension found here http://wiki.tcl.tk/25685 . Here a temporary download link of the slightly modified source http://www.waddell.ch/RnavGraph/imagescale_adrian_85.c The file works with the Tcl version 8.5. I've added the gcc compile commands I use for Linux, OSX and Windows (minGW) at the beginning of the file. I'm struggling to dynamically load the extension under Windows 7. That is i tried to use load imgscale.dll where under Linux and OSX I use load ./imgscale[info sharedlibextension] Now my Questions: does anybody know how to deal with this C extension such that when I distribute the R-package over CRAN it will work on every OS? This includes the question why I can not load the extension in Windows. Is there an R package out there which uses a C extension for a Tcl function from which I could learn how to do this? Thanks, Adrian