Image-Pixelator is a project mainly written in C++, it's free.
Blockify an image. Takes an image, and uses openCV to give all pixels in large regions of the image the value of the average pixel value of the region.
Image Pixelator Brandon Lucia 2011
This is a simple program that uses OpenCV to "blockify" an image. The idea is that a specified number of regions of the image are averaged, and a new image outputted, composed of the averaged regions computed.