Image processing system and its smoothing method for correcting color fog and backlight of a digital image

• US 6,097,836 A
• Filed: 07/22/1997
• Issued: 08/01/2000
• Est. Priority Date: 07/22/1996
• Status: Expired due to Term

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Inoue, Akira
• Primary Examiner(s): Nguyen, Madeleine Anh-Vinh
• Application Number:
  US08/898,132
• Time in Patent Office: 1,106 Days
• Field of Search: 358/518, 358/519, 358/520, 358/521, 358/523, 358/524, 358/525, 358/534, 358/1.9, 358/1.1, 358/1.3, 358/1.16, 382/162, 382/163, 382/165, 382/167
• US Class Current: 382/165
• CPC Class Codes: G06T 2207/10024 Color image
• CPC Class Codes: G06T 5/40 using histogram techniques
• CPC Class Codes: G06T 5/92 based on global image properties

Abstract

An image processing system including a correction pattern storing unit for storing correction patterns set corresponding to kinds of color fogs, a correction pattern selecting unit for selecting a correction pattern suitable for correction of input image, a correction amount storing unit for storing a correction amount indicative of an appropriate degree of correction on color fog, a tone curve generating unit for generating a tone curve of RGB based on a selected correction pattern and a correction amount stored in the correction amount storing unit, and an LUT converting unit for performing table conversion on image data of input image according to a generated tone curve to conduct color conversion processing of all the pixels of image data.

Claims

1. An image processing system which conducts necessary correction processing on digital image data, comprising:

correction pattern storing means for storing correction patterns set corresponding to kinds of color fogs;

correction pattern selecting means for selecting said correction pattern suitable for correction of an input image among said correction patterns stored in said correction pattern storing means through the operation of an operator;

correction amount storing means for storing a correction amount indicative of an appropriate degree of correction on color fog;

tone curve generating means for generating a tone curve of RGB based on said correction pattern selected by said correction pattern selecting means and said correction amount stored in said correction amount storing means; and

LUT converting means for performing table conversion on image data of said input image based on said tone curve generated by said tone curve generating means to conduct color conversion processing of all the pixels of image data, and

wherein said tone curve generating means comprises;

highlight control amount calculating means for calculating a control amount of a highlight region in each component of RGB based on said correction pattern and said correction amount,

half tone control amount calculating means for calculating a control amount of a half tone region in each component of RGB based on said correction pattern and said correction amount,

shadow control amount calculating means for calculating a control amount of a shadow region in each component of RGB based on said correction pattern and said correction amount,

tone curve calculating means for calculating said tone curve of each component of RGB based on the three kinds of control amounts calculated by said three kinds of control amount calculating means,

a straight line generating means for use in the tone curve calculating processing by said tone curve calculating means to conduct straight line interpolation between a control point in a high brightness region and a control point in a low brightness region, and

a curve generating means for use in the tone curve calculating processing by said tone curve calculating means to conduct curve interpolation for smoothly interpolating between a control point in a half tone region and starting points on the high brightness side and the low brightness side.

2. Digital image data correcting method in an image processing system which conducts necessary correction processing on digital image data, comprising the steps of:

among correction patterns set corresponding to kinds of color fogs, selecting said correction pattern suitable for correction of an input image by the operation of an operator;

obtaining a correction amount indicative of an appropriate degree of correction on color fog;

generating a tone curve of RGB based on said correction pattern selected at said correction pattern selecting step and said correction amount obtained at said correction amount obtaining step; and

performing table conversion on image data of said input image according to said tone curve generated at said tone curve generating step to conduct color conversion of all pixels of the image data, and

wherein said tone curve generating step comprises the steps of;

calculating a control amount of a highlight region in each component of RGB based on said correction pattern and said correction amount,

calculating a control amount of a half tone region in each component of RGB based on said correction pattern and said correction amount,

calculating a control amount of a shadow region in each component of RGB based on said correction pattern and said correction amount,

calculating said tone curve of each component of RGB based on the three kinds of control amounts calculated at each said steps, wherein

at the time of calculating a tone curve, said tone curve calculating step performing

a straight line generating module for conducting straight line interpolation between a control point in a high brightness region and a control point in a low brightness region, and

a curve generating module for conducting curve interpolation for smoothly interpolating between a control point in a half tone region and starting points on the high brightness side and on the low brightness side.

3. A computer readable memory which stores an image processing program for controlling an image processing system which conducts necessary correction processing on digital image data, said image processing program comprising the steps of:

among correction patterns set corresponding to kinds of color fogs, selecting said correction pattern suitable for correction of an input image by the operation of an operator;

obtaining a correction amount indicative of an appropriate degree of correction on color fog,

generating a tone curve of RGB based on said correction pattern selected at said correction pattern selecting step and said correction amount obtained at said correction amount obtaining step; and

performing table conversion on image data of said input image according to said tone curve generated at said tone curve generating step to conduct color conversion of all pixels of the image data,

and wherein said tone curve generating step of said image processing program comprises the steps of;

calculating a control amount of a highlight region in each component of RGB based on said correction pattern and said correction amount,

calculating a control amount of a half tone region in each component of RGB based on said correction pattern and said correction amount,

calculating a control amount of a shadow region in each component of RGB based on said correction pattern and said correction amount,

calculating said tone curve of each component of RGB based on the three kinds of control amounts calculated at each said steps, wherein

at the time of calculating a tone curve, said tone curve calculating step performing

a straight line generating module for conducting straight line interpolation between a control point in a high brightness region and a control point in a low brightness region, and

a curve generating module for conducting curve interpolation for smoothly interpolating between a control point in a half tone region and starting points on the high brightness side and on the low brightness side.

4. An image processing system which conducts necessary correction processing on digital image data, comprising:

correction pattern storing means for storing correction patterns set corresponding to kinds of color fogs;

correction pattern selecting means for selecting said correction pattern suitable for correction of an input image among said correction patterns stored in said correction pattern storing means through the operation of an operator;

correction amount storing means for storing a correction amount indicative of an appropriate degree of correction on color fog;

tone curve generating means for generating a tone curve of RGB based on said correction pattern selected by said correction pattern selecting means and said correction amount stored in said correction amount storing means; and

LUT converting means for performing table conversion on image data of said input image based on said tone curve generated by said tone curve generating means to conduct color conversion processing of all the pixels of image data, and

wherein said tone curve generating means comprises;

tone curve calculating means for calculating said tone curve of each component of RGB,

a straight line generating means for use in the tone curve calculating processing by said tone curve calculating means to conduct straight line interpolation between a control point in a high brightness region and a control point in a low brightness region, and

a curve generating means for use in the tone curve calculating processing by said tone curve calculating means to conduct curve interpolation for smoothly interpolating between a control point in a half tone region and starting point on the high brightness side and the low brightness side.

5. Digital image data correcting method in an image processing system which conducts necessary correction processing on digital image data, comprising the steps of:

among correction patterns set corresponding to kinds of color fogs, selecting said correction pattern suitable for correction of an input image by the operation of an operator;

obtaining a correction amount indicative of an appropriate degree of correction on color fog;

generating a tone curve of RGB based on said correction pattern selected at said correction pattern selecting step and said correction amount obtained at said correction amount obtaining step; and

performing table conversion on image data of said input image according to said tone curve generated at said tone curve generating step to conduct color conversion of all pixels of the image data, and

wherein said tone curve generating step comprises the step of;

calculating said tone curve of each component of RGB, wherein at the time of calculating a tone curve, said tone curve calculating step performing

a straight line generating module for conducting straight line interpolation between a control point in a high brightness region and a control point in a low brightness region, and

a curve generating module for conducting curve interpolation for smoothly interpolating between a control point in a half tone region and starting points on the high brightness side and on the low brightness side.

6. A computer readable memory which stores an image processing program for controlling an image processing system which conducts necessary correction processing on digital image data, said image processing program comprising the steps of:

among correction patterns set corresponding to kinds of color fogs, selecting said correction pattern suitable for correction of an input image by the operation of an operator;

obtaining a correction amount indicative of an appropriate degree of correction on color fog,

generating a tone curve of RGB based on said correction pattern selected at said correction pattern selecting step and said correction amount obtained at said correction amount obtaining step; and

performing table conversion on image data of said input image according to said tone curve generated at said tone curve generating step to conduct color conversion of all pixels of the image data,

and wherein said tone curve generating step of said image processing program comprises the step of;

calculating said tone curve of each component of RGB, wherein at the time of calculating a tone curve, said tone curve calculating step performing

a straight line generating module for conducting straight line interpolation between a control point in a high brightness region and a control point in a low brightness region, and

a curve generating module for conducting curve interpolation for smoothly interpolating between a control point in a half tone region and starting points on the high brightness side and on the low brightness side.