Image processing apparatus utilizing pixel values of peripheral pixels adjacent the subject pixel

An image processing apparatus for lossless compression of images, comprising:

• first generator for measuring the pixel values of three peripheral pixels adjacent to a subject pixel, and generating a first prediction signal from the measuring result;
• second generator for generating a second prediction signal which represents the average value of the maximum and the minimum out of the measured values of the three peripheral pixels;
• calculator for calculating a prediction error signal on the basis of the first prediction signal generated by said first generator and the pixel value of said subject pixel;
• comparator for comparing the first prediction signal generated by said first generator with the second prediction signal generated by said second generator;
• inverter for inverting, on the basis of the comparison result obtained from said comparator, the polarity of the prediction error signal calculated by said calculator;
• and
• invertercode word allocator for allocating a code word in accordance with the prediction error signal inverted in polarity by said inverter.