J An image scanning device for scanning both sides of a document with a simple memory structure and an image data outputting device for separating image data of each side from image data on both sides

摘要

The present invention relates to an image scanning apparatus for effectively compressing and encrypting image data obtained by scanning both sides of a document (2) by using a conventional line memory storing three lines. The image data output value of the first scanner 3 and the image data output values of the second scanner 4 are alternately outputted from the switching unit 5 on the basis of each line. The line memory 8 stores three consecutive lines of image data output information from the switching unit 5. The three lines include the current line including the current line, the immediately preceding line, and the second immediately preceding line preceding the immediately preceding line, and the current line is encrypted. The reference pixels are extracted from the current line of the line memory 8 and the pixels included in the line immediately preceding the second line. The pixel value of the current pixel is encrypted by using the predicted pixel value of the current pixel as a variable so as to output the encrypted image data corresponding to both sides of the original 2. [ The prediction of the pixel value is performed by inquiring reference pixels.