Image data processing method and apparatus therefor

Claim 2

An image data processing method for processing first image data obtained by optically reading the image of an original having gradation thereby to obtain second image data correctly reflecting said gradation of said original, said image data processing method comprising the steps of: (a) preparing a reference density plane having a known optical density; (b) reading the optical density of said reference density plane with a photoelectric converter while detecting an output level of said photoelectric converter to obtain a reference level data expressing said output level; (c) reading said image of said original by said photoelectric converter thereby to obtain the first image data; and (d) removing a background component from said first image data on the basis of said reference level data, thereby to obtain the second image data, said background component being outputted from said photoelectric converter independently of said image of said original.

Claim 3

An image data processing method in accordance with claim 1, wherein step (d) includes the step of obtaining a difference between said first image data and said reference level data whereby said background components included in both of said first image data and said reference level data cancel each other.

Claim 4

An image data processing method in accordance with claim 2, wherein said reference density plane includes a white reference density plane and a black reference density plane respectively having known optical density, said reference level data include white reference level data and black reference level data, step (b) includes the steps of: (b-1) reading the optical density of said white reference density plane by said photoelectric converter to obtain said white reference level data; and (b-2) reading the optical density of said black density reference plane by said phtoelectric converter to obtain said black reference level data, and step (d) includes the steps of: (d-j) obtaining a first difference between said first image data and said black reference level data; (d-2) obtaining a second difference between said white reference level data and said black reference level data; and (d-3) dividing said first difference by said second difference.

Claim 5

An image data processing method in accordance with claim 3, wherein said background component is removed from said first image data through a shading correction of said first image.

Claim 6

An image data processing method in accordance with claim 4, wherein said first image data are converted into data having positive/negative sign in said shading correction.

Claim 7

6: An image data procesing method in accordance with claim 1, wherein step (b) includes the steps of: (b-1) obtaining a value of a background parameter expressing the intensity of said background component on the basis of said reference level data; (b-2) modifying a previously given image correction curve by an amount in accordance with said value of said . background parameter to obtain a modified image correction curve, and (b-3) removing said background component from said first image data by correcting said first image data in accordance with said modified image correction curve.

Claim 8

An image data procesing method in accordance with claim 6, wherein said image correction curve is a gradation correction curve, and said image correcting includes gradation correcting.

Claim 9

An image data processing method in accordance with claim 7, wherein said value of said background parameter is employed in common for each original.

Claim 10

An image data processing method in accodance with claim 7, wherein said value of said background parameter is independently obtained for each original.

Claim 11

An image data processing apparatus for processing first image data obtained by optically reading the image of an original having gradation thereby to obtain second image data correctly reflecting said gradation of said original, said image data processing apparatus comprising: (a) a reference density plane having a known optical density; (b) photoelectric conversion means for reading said optical density of said reference density plane and said image of said original; (c) memory means for storing reference level data obtained by reading said optical density of said reference density plane by said photoelectric conversion means; (d) shading correction means for receiving the first image data obtained by reading said image of said original by said photoelectric conversion means for performing shading correction on said first image data, said shading correction means having: (d-1) read means for reading said reference level data from said memory means; and (d-2) arithmetic means for obtaining a difference between said first image data and said reference level data to output a signal responsive to said difference; and (e) means for generating the second image data on the basis of the output signal from said shading correction means.

Claim 12

An image data processing apparatus for processing first image data obtained by optically reading the image of an original having gradation thereby to obtain second image data correctly reflecting said gradation of said original, said image data processing apparatus comprising: (a) a reference density plane having a known optical density; (b) photoelectric conversion means for reading said optical density of said reference density plane and said image of said original; (c) memory means for storing reference level data obtained by reading said optical density of said reference density plane by said photoelectric conversion means; (d) shading correction means for receiving the first image data obtained by reading said image of said original by said photoelectric conversion means for performing shading correction on said first image data, said shading correction means having: (d-1) read means for reading said reference level data from said memory means; and (d-2) arithmetic means for obtaining a difference between said first image data and said reference level data to output a signal responsive to said difference; and (e) means for generating the second image data on the basis of the output signal from said shading correction means.

Claim 13

An image data processing appratus in accordance with claim 10, wherein said reference density plane includes a white reference density plane and a black reference density plane respectively having known optical density, said reference level data include white reference level data and black reference density level, said arithmetic means includes: first subtraction means for obtaining a first difference between said black reference level data and said first image data, second subtraction means for obtaining a second difference between said white reference level data and said black reference level data; dividing means for dividing said first difference by said second difference to provide a difference ratio signal, and means for generating said second image data in response to said difference ratio signal.

Claim 14

An image data processing aparatus in accordance with claim 11, wherein said first image data are converted into data having positive/negative sign in said shading correction means.

Claim 15

An image data processing apparatus for processing first image data obtained by optically reading the image of an original having gradation thereby to obtain second image data. correctly reflecting said gradation of said original, said image data processing apparatus comprising: (a) photoelectric conversion means for reading said image of said original; (b) memory means for previously storing the value of a background parameter expressing the intensity of a background component outputted from said photoelectric conversion means independently of said image of said original; and (c) background correction means for performing background correction on the first image data obtained by reading said image of said original by said photoelectric conversion means in response to said value of said background parameter read from said memory means thereby to obtain the second image data.

Claim 16

An image data processing apparatus for processing first image data obtained by optically reading the image of an original having gradation thereby to obtain second image data. correctly reflecting said gradation of said original, said image data processing apparatus comprising: (a) photoelectric conversion means for reading said image of said original; (b) memory means for previously storing the value of a background parameter expressing the intensity of a background component outputted from said photoelectric conversion means independently of said image of said original; and (c) background correction means for performing background correction on the first image data obtained by reading said image of said original by said photoelectric conversion means in response to said value of said background parameter read from said memory means thereby to obtain the second image data.

Claim 17

An. image data processing apparatus in accordance with claim 13, wherein said background correction means also serves as gradation correction means for performing a gradation correction on said first image data, said background correction means having: (c-1) storage means for storing first. gradation correction data previously prepared for a case of an absence of said background component, (c-2) arithmetic means for obtaining second gradation correction data for a case of a presence of said background component on the basis of said first gradation correction data read from said strage means and said value of said background parameter read from said memory means; and (c-3) a look-up table memory for storing said second gradation correction data for performing said background correction and said gradation correction on said first image data.