Abstract: A circuit is disclosed to simplify hardware of image transmission system such as a facsimile and also improve an encoding function. This circuit has a part for obtaining from a brightness change detector a brightness signal indicative of a change of brightness of binary valued data serially supplied from a data input part, and providing a detection load data to a storage part in response to generation of said detection signal. Accordingly, the storage part generates a within-line position value for said binary valued data having a change of brightness in response to the detection load data.

Abstract: An arithmetic coding method for encoding each pixel of image containing half-tones in an image processing system is provided. This method includes the steps of: initializing an encoder before encoding each line; reading a pixel of a dithered image signal; determining reference pixels being an immediately preceding pixel, and a preceding pixel by a horizontal size of a dithering matrix for the read pixel; selecting a corresponding context number according to the values of the two reference pixels and a remainder obtained by dividing a horizontal position of the read pixel by the horizontal size of the dithering matrix; identifying context information corresponding to the context number, the context information including a more probable symbol and a probability therefor; encoding the more probable symbol if it matches the read pixel value, and encoding a less probable symbol otherwise; and updating a probability estimation of the context information.