Abstract: An image processing apparatus by which an excellent image can be obtained even after compression and expansion. A compression circuit (12) has a line scanning unit which divides original image data into color data groups in relation to respective pixels, a line compression unit (24) which expresses the value (y) of the color data corresponding to each pixel position in a predetermined section with a polynomial: y=ax3+bx2+cx+d wherein (x) denotes the pixel position which is a variable and a coefficient calculation unit (26) which obtains the color data values corresponding to the respective pixel positions in accordance with the received coefficients and pixel positions. The restored image data are outputted to a display apparatus, etc.