Abstract: An image sensing element for providing a series of voltage signals corresponding to a two-dimensional image, a two-dimensional analog DCT (discrete cosine transform) circuit for performing a two-dimensional DCT on the voltage signal series from the image sensing element in pixel blocks, and a quantization circuit for quantizing a result of the DCT are provided. The two-dimensional analog DCT circuit is formed of a row of analog sum-of-products arithmetic units for one-dimensional DCT and an analog memory array for matrix transposition. The quantization circuit converts a voltage representing a result of the DCT carried out by the two-dimensional analog DCT circuit into a digital value according to a given quantization coefficient Q=2.sup.N .multidot.S(1.ltoreq.S<2) wherein a voltage S.multidot.Vref that is S times greater than a fixed voltage Vref serves as a reference voltage, and performs a process of right-shifting the digital value N bits in order to provide a quantized digital value.