An image processor which processes an image signal using a DSP (digital signal processor), wherein a shading correction process, a logarithmic transformation process, an edge emphasizing process, a density adjustment process and a binarization process of the like are performed utilizing the DSP and a look-up table outside the DSP. An image signal is input in an order of raster scanning, and each pixel data of the image signal is set to an input register of the DSP. Calculations necessary for shading correction are performed in parallel on the pixel data by a plurality of ALUs in the DSP, and a logarithmic transformation is performed on the calculation results utilizing the look-up table. Further, the logarithmically-transformed signal is input to the DSP and set to the input register for an edge emphasizing process which is performed by the plurality of ALUs. The result is again input to the look-up table for a density adjustment process and input to the DSP for binarization and subsequent output.