1. An image reducing device that converts original image data into reduced image data with less pixels, said image reducing device comprising: a simple-averaging device that calculates a simple average of data of a plurality of pixels of each simple-averaging area of the original image data to acquire a pixel of middle image data of each simple-averaging area; and a weighted-averaging device that multiplies data of pixels of the middle image data that are adjacent to a pixel of the reduced image data by weight coefficients according to positions of the pixel of the reduced image data and the pixels of the middle image data to acquire the pixel of the reduce image data.