EP0395404A2 — Image processing apparatus

Claim 1

Independent Claim 95 words

Image processing apparatus which divides the image into the 1st and 2nd regions and executes quantization region by region, said apparatus comprising: input means to input the data of objective pixel; calculating means to obtain the average density value in the specified region; and quantization means to quantize the data of the said objective pixel based on the average density value obtained by the said calculation means, wherein the said quantization means quantize the data of the objective pixel in such way that a continuity is secured between the said 1st and the 2nd regions.

Claim 2

Dependent Claim 95 words

Image processing apparatus which divides the image into the 1st and 2nd regions and executes quantization region by region, said apparatus comprising: input means to input the data of objective pixel; calculating means to obtain the average density value in the specified region; and quantization means to quantize the data of the said objective pixel based on the average density value obtained by the said calculation means, wherein the said quantization means quantize the data of the objective pixel in such way that a continuity is secured between the said 1st and the 2nd regions.

Claim 3

Dependent Claim 62 words

An apparatus according to claim 1, wherein the said quantization means, when quantizing the data of the pixel in the 2nd region, overlappingly reads the data of the said 1st region and binarizes the data of the objective pixel based on the average density value obtained from the multi-level data of the 1st region and the binary data of the 2nd region.

Claim 4

Dependent Claim 75 words

An apparatus according to claim 1, wherein a memory to store the binary data obtained by binarizing the pixel in the said 1st region is provided and the said quantization means, at the quantization of the data of the pixel in the 2nd region, binarizes the data of the objective pixel based on the average density value obtained from the binary data stored in the said memory and the binary data in the 2nd region.

Claim 5

Dependent Claim 60 words

An apparatus according to claim 1, wherein the said quantization means is provided with the means to execute correction by adding the error generating at the quantization on to the pixel not processed yet and the memory means to temporarily store the said error in order to add it to the pixel in the region succeeding the region being processed.

Claim 6

Dependent Claim 52 words

An apparatus according to claim 1, wherein the said calculation means calculates the average density m₁ in the specified region when the data of the objective pixel are quantized into 1 and the average density value m₂ in the specified region when the data of the objective pixel are quantized to 0.

Claim 7

Dependent Claim 26 words

An apparatus according to claim 5, wherein the said calculation means calculates the average density value in the specified region by using the specified weight mask.

Claim 8

Dependent Claim 26 words

An apparatus according to claim 5, wherein the said quantization means binarizes the data of the objective pixel by using (m₁ + m₂)/2 as the threshold.

Claim 9

Dependent Claim 39 words

An apparatus according to claim 1, wherein the said input means input the data obtained by adding the error data having generated at the quantization of the pixel preceding the objective pixel on to the data of objective pixel.

Claim 10

Dependent Claim 30 words

An apparatus according to claim 1, wherein the said calculating means calculate the average value m from the data of the specified region already quantized which precedes the objective pixel.

Claim 11

Dependent Claim 36 words

An apparatus according to claim 9, wherein the said calculating means comprises a read only memory (ROM) which uses the said quantized data in the specified region as address and outputs the average density value m.

Claim 12

Dependent Claim 28 words

An apparatus according to claim 9, wherein the said quantization means binarizes the data of the objective pixel by using the said average density value m as threshold.

Claim 13

Dependent Claim 81 words

An image processing apparatus which binarizes the multi-level image data by the average value based on the binary data of the specified range having been already binarized, said apparatus comprising: discriminating means to judge that there is no binary data at least at a part of the said specified range; and multiple-level data replacing means which replaces the pixel having been judged to have no binary data for the value obtained by normalizing the multiple-level data by the said discriminating means.

Claim 14

Dependent Claim 81 words

An image processing apparatus which binarizes the multi-level image data by the average value based on the binary data of the specified range having been already binarized, said apparatus comprising: discriminating means to judge that there is no binary data at least at a part of the said specified range; and multiple-level data replacing means which replaces the pixel having been judged to have no binary data for the value obtained by normalizing the multiple-level data by the said discriminating means.

Claim 15

Dependent Claim 40 words

An apparatus according to claim 12, wherein the said apparatus is further provided with the error diffusion means to diffuse the error produced by the said binarization and the error propagation means to propagate the said error between different scans.

Claim 16

Dependent Claim 103 words

Image processing apparatus comprising: input means to input the data of the objective pixel; calculation means to obtain the average density value in the specified region proceding the objective pixel which has been already binarized; binarization means to binarize the data of the said objective pixel based on the output of the said calculation means; correction means to correct the error generating at the binarization of the said objective pixel; and data preserving means to preserve the output of the said binarization means or the output of the said binarization means and the output of the said correction means for a specified period.

Claim 17

Dependent Claim 103 words

Image processing apparatus comprising: input means to input the data of the objective pixel; calculation means to obtain the average density value in the specified region proceding the objective pixel which has been already binarized; binarization means to binarize the data of the said objective pixel based on the output of the said calculation means; correction means to correct the error generating at the binarization of the said objective pixel; and data preserving means to preserve the output of the said binarization means or the output of the said binarization means and the output of the said correction means for a specified period.

Claim 18

Dependent Claim 54 words

An apparatus according to claim 14, wherein the said calculation means and binarization means execute calculation of the average density value and binarization of the pixel in the region succeeding the 1st region using the output of binarization means preserved in the said data preservation means, after completion of binarization of the 1st region.

Image processing apparatus

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