Lodepng is a png codec without external dependencies. It has a high-level simple procedural interface for encoding and decoding and exposes a low level interface primarily for editing purposes. It was originally ported from the C++ version written by Lode Vandevenne.
Lodepng can be downloaded via dsss: dsss net install lodepng -doc, this will also install the documentation. Lodepng should work with both GDC and DMD (the 1.x branch) as well as Phobos and Tango. (Tested with gdc-tango, dmd-tango and dmd-phobos on linux)
The documentation is also browsable online: