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This filter is unlikely to be widely useful; it was developed due to a specific request on It's probably most useful as a template/example/demo of a simple cross-platform filter.

It merely quantises each channel of an image into 16 values, essentially taking the most significant four bits of each pixel value and multiplying by 17 to keep the range from 0-255: output values are therefore 0*17,1*17...15*17 (255). A full colour RGB image will be reduced to a maximum of 4096 colours.

Source code is provided for building with

  • MPW (targeting MacOS) MPW runs on PowerPC and 68K Macs under Mac OS 9 or earlier, or Classic under OS X.
  • mingw32 (targeting Windows). MinGW32 can be hosted on virtually any UNIX or Linux system, or under Windows; it is open source and GNU-based.
  • Borland C++ Builder (targeting Windows).
These development systems are all freely available.

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