Information embedding apparatus and information embedding method for adding information to document image by embedding information therein, information detecting apparatus and information detecting method

1. An information embedding apparatus comprising:

an embedding pattern storing portion for storing a plurality of types of embedding dot patterns;

an embedding pattern reading portion for reading said embedding dot pattern indicating an information to be embedded in a background of a document image from said embedding pattern storing portion; and

an embedding compositing portion for compositing said embedding dot pattern read by said embedding pattern reading portion with the background of said document image in a document image data generated based on a document data and outputting said document image data composited with said embedding dot pattern, wherein

said embedding dot pattern includes a data dot placed at a position in accordance with said information to be embedded, a position dot placed at a position for instructing a reference position used for identifying the position of said data dot, and an assisting dot placed at a position for assisting the instruction of the reference position by said position dot.

2. The information embedding apparatus according to claim 1 , further comprising:

an additional pattern storing portion for storing a plurality of types of additional dot patterns indicating dot patterns different from said embedding dot patterns;

an additional pattern reading portion for reading said additional dot pattern indicating the information to be added to the background of said document image from said additional pattern storing portion; and

an addition compositing portion for compositing said additional dot pattern read by said additional pattern reading portion with the background of said document image in said document image data generated based on said document data and outputting said document image data composited with the additional dot pattern.

3. The information embedding apparatus according to claim 2 , wherein

said different additional patterns corresponding to a plurality of different values are stored in said additional pattern storing portion, and

said additional pattern reading portion reads said information to be added as an element value and reads the additional dot pattern corresponding to the read element value from said additional pattern storing portion.

4. The information embedding apparatus according to claim 2 , wherein a dot density is different in each of said plurality of types of said additional dot patterns.

5. The information embedding apparatus according to claim 4 , wherein said additional dot pattern includes an independent dot.

6. The information embedding apparatus according to claim 1 , wherein

the different embedding dot patterns corresponding to a plurality of different values are stored in said embedding pattern storing portion,

said embedding pattern reading portion includes an embedding data forming portion for converting said information to be embedded into a bit sequence indicating the information, and

said embedding pattern reading portion reads said embedding dot pattern corresponding to a value of each bit in said bit sequence converted by said embedding data forming portion from said embedding pattern storing portion.

7. The information embedding apparatus according to claim 1 , further comprising an addition compositing portion for compositing an additional dot pattern indicating a dot pattern different from said embedding dot pattern with the background of said document image in said document image data generated based on said document data for outputting said document image data composited with the additional dot pattern, wherein

said addition compositing portion compares a threshold value previously set in each element in a threshold pattern presented by a two-dimensional element matrix having a same size as that of the background of said document image to a corresponding element value in the background, and outputs the corresponding element value to said document image data composited with said embedding dot pattern in accordance with a result of the comparison.

8. The information embedding apparatus according to claim 1 , wherein

said embedding dot pattern indicates a unit pattern having a plurality of predetermined elements two-dimensionally arranged, and

the embedding compositing portion adjacently places a plurality of said embedding dot patterns read by said embedding pattern reading portion in the background of said document image.

9. An information embedding method comprising the steps of:

reading an embedding dot pattern indicating information to be embedded in a background of a document image from an embedding pattern storing portion in which a plurality of types of the embedding dot patterns are stored: and

compositing said embedding dot pattern read in said step of reading the embedding pattern with the background of said document image in a document image data generated based on a document data and outputting said document image data composited with said embedding dot pattern, wherein

said embedding dot pattern includes a data dot placed at a position in accordance with said information to be embedded, a position dot placed at a position for instructing a reference position used for identifying the position of said data dot, and an assisting dot placed at a position for assisting the instruction of said reference position by said position dot.

10. The information embedding method according to claim 9 , wherein

said embedding dot pattern indicates a unit pattern having a plurality of predetermined elements two-dimensionally arranged, and

the plurality of embedding dot patterns read in said step of reading the embedding pattern are adjacently placed in the background of said document image in the embedding compositing step.