Loss-less compression of still images at enhanced speed

A method of compressing a stream of pixel data relative a two-dimensional object, pixels of which are scanned by rows from a source device to a receiver device, includes defining an extended context window to include a pair of pixels following a last encoded pixel on the row being scanned and the respective triplets of neighboring pixels belonging to the preceding row. The method includes defining a first distinct context array of pixels of the extended context window for the pixel of the pair immediately following the last encoded pixel, and a second context array of pixels of the extended context window for the other pixel of the pair. An extended context value relative to each pixel of the pair is calculated, and the extended context value relative to a first pixel immediately following the last encoded pixel is compared with an extended threshold. If the extended context value is less than the extended threshold, then encoding the first and second pixels of the pair, and if the extended context value relative to the first pixel of the pair exceeds the extended threshold, then carrying out simultaneously a parallel processing and encoding of both pixels according to an encoding routine.