Image processing apparatus

Claim 2

An image processing apparatus, comprising: an input means for inputting data on an object pixel; a calculation means for calculating an average density value of a predetermined area; and a quantization means for converting the data on said object pixel into multi-level data on the basis of the average density value obtained by said calculation means.

Claim 3

An image processing apparatus according to claim 1, wherein said calculation means calculates the average density value using data consisting of a bit deleted from those of the multi-level data consisting of a plurality of bits and obtained by said quantization means.

Claim 4

An image processing apparatus according to claim 1 or claim 2, further comprising a correction means for correcting an error generated when the data on said object pixel is converted into the multi-level data.

Claim 5

An image processing apparatus according to claim 3, wherein said correction means corrects a difference between the data on said object pixel which is input and the average density value which is obtained by quantizing the data on said object pixel as the error.

Claim 6

An image processing apparatus according to claim 3, wherein said correction means corrects the error when said error is within a predetermined value.

Claim 7

An image processing apparatus according to any one of claims to 3, wherein said calculation means calculates a plurality of average density values which are to be obtained when the data on said object pixel is quantized into a plurality of multi-level data.

Claim 8

An image processing apparatus according to claim 6, wherein said quantization means calculates a plurality of thresholds from said plurality of average density values and converts the data on said object pixel into the multi-level data on the basis of said plurality of thresholds.

Claim 9

An image processing apparatus according to any one of claims 1 to 3, further comprising a recording means for recording an image on the basis of said multi-level data, and a conversion means for converting said multi-level data and thereby correcting non-linear characteristics of said recording means.

Claim 10

An image processing apparatus, comprising: an average density calculation means for calculating an average density on the basis of a plurality of re-quantized data on the pixels in the vicinity of an object pixel which have already been re-quantized so that they take at least 3 levels; a threshold calculation means for calculating a plurality of thresholds on the basis of said average density; a re-quantization means for re-quantizing multi-level image data to image data that can take at least 3 levels on the basis of said plurality of thresholds; and a conversion means for converting the re-quantized image data in accordance with non-linear characteristics of a recording means.

Claim 11

An image processing apparatus, comprising: an average density calculation means for calculating an average density on the basis of a plurality of re-quantized data on the pixels in the vicinity of an object pixel which have already been re-quantized so that they take at least 3 levels; a threshold calculation means for calculating a plurality of thresholds on the basis of said average density; a re-quantization means for re-quantizing multi-level image data to image data that can take at least 3 levels on the basis of said plurality of thresholds; and a conversion means for converting the re-quantized image data in accordance with non-linear characteristics of a recording means.

Claim 12

An image processing apparatus according to claim 9, further comprising an error diffusion means for diffusing an error generated by the re-quantization conducted by said re-quantization means to pixels which will be re-quantized later.

Claim 13

An image processing apparatus, comprising: a re-quantization means for re-quantizing multi-level image data to image data that can take at least 3 levels on the basis of a plurality of re-quantized data on the pixels in the vicinity of an object pixel which have already been re-quantized; and a recording signal output means for non-linearly converting the re-quantized image data in accordance with density characteristics of an image recording means connected to said re-quantizing means and for outputting it to said image recording means.

Claim 14

An image processing apparatus, comprising: a re-quantization means for re-quantizing multi-level image data to image data that can take at least 3 levels on the basis of a plurality of re-quantized data on the pixels in the vicinity of an object pixel which have already been re-quantized; and a recording signal output means for non-linearly converting the re-quantized image data in accordance with density characteristics of an image recording means connected to said re-quantizing means and for outputting it to said image recording means.

Claim 15

An image processing apparatus according to claim 11, wherein said re-quantizing means includes an error diffusion means for diffusing an error caused by the re-quantization to pixels which will be re-quantized later.

Claim 16

An image processing method or apparatus in which the value of an optical characteristic of a pixel is determined, and the characteristic of the pixel is quantized, to a selected one of more than two available levels, using the determined value of the said characteristic and a threshold value.

Claim 17

An image processing method or apparatus in which the value of an optical characteristic of a pixel is determined, and the characteristic of the pixel is quantized, to a selected one of more than two available levels, using the determined value of the said characteristic and a threshold value.

Claim 18

An image processing method or apparatus in which the value of an optical characteristic of a pixel is determined, and the characteristic of the pixel is quantized using the determined value of the said characteristic, a correction value, and a threshold value, and an error arising from the quantization is used in the generation of the correction value for use in quantization of another nearby pixel.

Claim 19

An image processing method or apparatus in which the value of an optical characteristic of a pixel is determined, and the characteristic of the pixel is quantized using the determined value of the said characteristic, a correction value, and a threshold value, and an error arising from the quantization is used in the generation of the correction value for use in quantization of another nearby pixel.

Claim 20

An image processing method or apparatus according to claim 13 or claim 14 in which the threshold value is derived from the value of the characteristic of other nearby pixels.

Claim 21

An image processing method or apparatus according to claim 15 in which in deriving the threshold value, the value of the characteristic of other nearby pixels is specified to a smaller number of digits than the number of digits in the quantized value.