This package is part of Img, and refers to the libz support library needed by some of the image formats (like png). For easier handling by the package system, for wrapping, etc. the sources of libz were stub-sified and wrapped into a Tcl package, which was given the name zlibtcl to distinguish it from the unmodified libz.

In 8.6, largely superseded by the built-in zlib command (and its concomitant C API).

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