1. An apparatus for providing a bilevel image signal corresponding to multilevel image data obtained from an original image, said apparatus comprising: a) matrix register means for reading an original image for each area containing a predetermined number of pixels of the original image, and for extracting multilevel image data corresponding to said pixels of said read area, said pixels including a target pixel and neighboring pixels surrounding the target pixel; b) averaging means for calculating the average of multilevel image data of: (A) the target pixel, and (B) neighboring pixels excluding a specific neighboring pixel located below and to the right of the target pixel, extracted by said matrix register means for each area of the original image; c) binarization means for providing a bilevel image signal corresponding to the multilevel image data of the target pixel by using the average of the multilevel image data from the averaging means as a threshold value of binarization; and d) area detecting means for detecting whether or not the target pixel of the read area is in a uniform density area of the original image, based on whether or not the differences in multilevel image data between the target pixel and the respective neighboring pixels are smaller than a given reference value, and for supplying the result of the area detection for each pixel; wherein said binarization means provides: A) a bilevel image signal corresponding to the multilevel image data of the target pixel by using a fixed threshold value, when the target pixel is detected to be in a uniform-density area, and B) a bilevel image signal corresponding to the multilevel image data of the target pixel by using the average of the multilevel image data from the averaging means as the threshold value, when the target pixel is detected not to be in a uniform-density area.