Abstract: A barcode-embedding area is obtained in a color image based on expression possibility by the juxtaposed additive color mixture and possibility of reading of pixels separately by a barcode reader (S11), a color image in the barcode-embedding area is expressed by the juxtaposed additive color mixture, and color images for the code area and the background area, which are readable by the barcode reader, are created (S12, S13), a color-image-superimposed barcode image is created by using the color images for the code area and the background area, and the same color-image-superimposed barcode image is embedded in the barcode-embedding area (S14), and the color-image-superimposed barcode image and the original color image are corrected if necessary (S15, S16).

Abstract: First, a set of seed images that tally with each other are prepared (S101). Next, a set of threshold matrices are created from the set of seed images (S102). Next, a plurality of tally images are created from an input gray-scale image by using the set of threshold matrices (S103). The tally images are combined, whereby the confidential image is decoded.

Abstract: A barcode-embedding area is obtained in a color image based on expression possibility by the juxtaposed additive color mixture and possibility of reading of pixels separately by a barcode reader (S11), a color image in the barcode-embedding area is expressed by the juxtaposed additive color mixture, and color images for the code area and the background area, which are readable by the barcode reader, are created (S12, S13), a color-image-superimposed barcode image is created by using the color images for the code area and the background area, and the same color-image-superimposed barcode image is embedded in the barcode-embedding area (S14), and the color-image-superimposed barcode image and the original color image are corrected if necessary (S15, S16).

Abstract: A second tally image generating means 20 that outputs a pixel value B1m,n of a second tally image B1 includes a decoding-time peripheral luminance value calculating section composed of a decoded pixel value calculating means 28 and a peripheral luminance value calculating means 29. The decoding-time peripheral luminance value calculating means 29 calculates a luminance value dm,n around a currently processed pixel. A confidential-image embedding means 26 calculates a pixel value B1m,n of a second tally image B1 by use of a temporarily determined pixel value B1tm,n, a luminance value Sm,n of a confidential image S, a pixel value B0m,n of a first tally image B0 and the peripheral luminance value dm,n.

Abstract: First, a set of seed images that tally with each other are prepared (S101). Next, a set of threshold matrices are created from the set of seed images (S102) Next, a plurality of tally images are created from an input gray-scale image by using the set of threshold matrices (S103). The tally images are combined, whereby the confidential image is decoded.