Abstract: A digital data false alteration detection program causes a computer to execute (a) a step (S1) of dividing digital data into a plurality of smaller block data, (b) a step (S2) of extracting noise inherent to a digital data acquisition device for each of the small block data, (c) a step (S3) of calculating correlation of the noise between adjacent small block data, and (d) a step (S4) of detecting small block data having noise correlation lower than a level predetermined for the surrounding small block data, as falsely altered data.

Abstract: In a method for improving the color reproducibility of printed matter to be produced by a printing press in proof print produced by a proof press, a look-up table containing converted values of image data over the entire color space with respect to the proof press is created, the look-up table is corrected based on the color of a printing paper for the printing press and a paper exposed area factor in the proofing, and proof print is created by the use of the corrected look-up table.

Abstract: An original reference value table containing converted values of image data on the entire color space is made based on known look-up tables of a printer and a correction printer, and a reference value table is wholly or partly corrected adequately so that the results of printing performed by the correction printer by referring to the original reference value table may be similar to the results of printing performed by the printer while the mutual non-linearity of converted values held in the reference value table is maintained, thus making a reference value table with an improved precision of color reproduction.