1. An image reducing apparatus comprising: an orthogonal transform coefficient deciding device for deciding orthogonal transform coefficients, which are used to generate a reduced image, in accordance with a reduction ratio from among orthogonal transform coefficients that constitute a complete orthogonally transformed block, wherein the complete orthogonally transformed block is obtained by orthogonally transforming a complete image block having a predetermined plurality of pixels, from among a plurality of orthogonally transformed blocks each composed of a plurality of orthogonal transform coefficients that are the result of orthogonally transforming each image block of a plurality of image blocks that form one frame of an original image, each image block being composed of a plurality of pixels; a first reduced image block generating device for executing inverse orthogonal transformation processing using the orthogonal transform coefficients decided by said orthogonal transform coefficient deciding device, thereby generating a first reduced image block; a padded image block restoring device for applying inverse orthogonal transformation processing to a padded orthogonally transformed block obtained by orthogonally transforming a padded image block that is the result of adding padding data to a deficient image block, which does not possess the predetermined plurality of pixels, among the plurality of orthogonally transformed blocks in such a manner that the deficient image block will have the predetermined plurality of pixels, thereby restoring the padded image block; a modified image block generating device for generating a modified image block obtained by replacing the padding data, which is included in the padded image block restored by said padded image block restoring device, with data that is the result of copying original image data included in the padded image block; a second reduced image block generating device for generating a second reduced image block by reducing the modified image block, which has been generated by said modified image block generating device, in accordance with the reduction ratio; and a reduced image generating device for generating a reduced image, which conforms to the reduction ratio, from the first reduced image block generated by said first reduced image block generating device and the second reduced image block generated by said second reduced image block generating device.