Image coding/decoding method, image coding apparatus and image decoding apparatus for obtaining decoded images having small distortion in DCT based standard coding/decoding
First Claim
1. An image coding/decoding method in which an image coding apparatus sends coded information which is obtained by coding an original image to an image decoding apparatus and said image decoding apparatus decodes said coded information to obtain a reproduced image, said method comprising the steps of:
- extracting edge information which is binary information representing an edge part of said original image;
obtaining density information of an edge unsharpened image from said original image by unsharpening said edge part using said edge information, unsharpening the edge part includes obtaining density information x′
of a pixel of said edge part of said edge unsharpened image according to a first equation x′
=(1−
λ
)x+λ
C, wherein λ
is a positive constant, x is density information of said pixel of said original image, and C is surrounding density information representing density state of a surrounding region of said pixel;
obtaining coded edge information by coding said edge information according to a first coding algorithm;
obtaining coded density information by coding said density information of said edge unsharpened image according to a second coding algorithm;
sending said coded edge information and said coded density information as said coded information to said image decoding apparatus; and
said image decoding apparatus performing the steps of;
obtaining said edge information by decoding said coded edge information according to a first decoding algorithm corresponding to said first coding algorithm;
obtaining said density information of said edge unsharpened image by decoding said coded density information according to a second decoding algorithm corresponding to said second coding algorithm;
obtaining said reproduced image from said density information of said edge unsharpened image by restoring said edge part of said edge unsharpened image by using said edge information and using a predetermined equation according to a steepest-descent method, said predetermined equation being defined on the basis of a relationship between said density information x′
formulated by said first equation and restored density information;
wherein said second coding algorithm and said second decoding algorithm are based on a standard coding method using a discrete cosine transform, and wherein all the above steps are performed using one or more processors.
2 Assignments
0 Petitions
Accused Products
Abstract
An image coding method is provided, in which the method includes the steps of: extracting edge information which represents an edge part of an original image; obtaining density information of an edge smoothed image from the original image by smoothing the edge part; obtaining coded edge information by coding the edge information according to a first coding algorithm; obtaining coded density information by coding the density information of the edge smoothed image according to a second coding algorithm; and sending the coded edge information and the coded density information as coded information to an image decoding apparatus.
28 Citations
24 Claims
-
1. An image coding/decoding method in which an image coding apparatus sends coded information which is obtained by coding an original image to an image decoding apparatus and said image decoding apparatus decodes said coded information to obtain a reproduced image, said method comprising the steps of:
-
extracting edge information which is binary information representing an edge part of said original image; obtaining density information of an edge unsharpened image from said original image by unsharpening said edge part using said edge information, unsharpening the edge part includes obtaining density information x′
of a pixel of said edge part of said edge unsharpened image according to a first equation x′
=(1−
λ
)x+λ
C, wherein λ
is a positive constant, x is density information of said pixel of said original image, and C is surrounding density information representing density state of a surrounding region of said pixel;obtaining coded edge information by coding said edge information according to a first coding algorithm; obtaining coded density information by coding said density information of said edge unsharpened image according to a second coding algorithm; sending said coded edge information and said coded density information as said coded information to said image decoding apparatus; and said image decoding apparatus performing the steps of; obtaining said edge information by decoding said coded edge information according to a first decoding algorithm corresponding to said first coding algorithm; obtaining said density information of said edge unsharpened image by decoding said coded density information according to a second decoding algorithm corresponding to said second coding algorithm; obtaining said reproduced image from said density information of said edge unsharpened image by restoring said edge part of said edge unsharpened image by using said edge information and using a predetermined equation according to a steepest-descent method, said predetermined equation being defined on the basis of a relationship between said density information x′
formulated by said first equation and restored density information;wherein said second coding algorithm and said second decoding algorithm are based on a standard coding method using a discrete cosine transform, and wherein all the above steps are performed using one or more processors. - View Dependent Claims (2, 3, 4, 5)
-
-
6. An image coding/decoding method in which an image coding apparatus sends coded information which is obtained by coding an original image to an image decoding apparatus and said image decoding apparatus decodes said coded information to obtain a reproduced image, said method comprising the steps of:
-
extracting edge information which is binary information representing an edge part of said original image; converting said edge information which is binary information into a distance map including distance values between pixels of said edge part and other pixels; obtaining density information of an edge unsharpened image from said original image by unsharpening said edge part using said distance map; obtaining coded edge information by coding said edge information according to a first coding algorithm; obtaining coded density information by coding said density information of said edge unsharpened image according to a second coding algorithm; sending said coded edge information and said coded density information as said coded information to said image decoding apparatus; and said image decoding apparatus performing the steps of; obtaining said edge information by decoding said coded edge information according to a first decoding algorithm corresponding to said first coding algorithm; obtaining said density information of said edge unsharpened image by decoding said coded density information according to a second decoding algorithm corresponding to said second coding algorithm; obtaining said reproduced image from said density information of said edge unsharpened image by restoring said edge part of said edge unsharpened image by using said edge information; wherein said second coding algorithm and said second decoding algorithm are based on a standard coding method using a discrete cosine transform, and wherein all the above steps are performed using one or more processors.
-
-
7. An image coding apparatus comprising:
-
an edge extracting part for extracting edge information which is binary information representing an edge part of an original image; an edge unsharpening part for obtaining density information of an edge unsharpened image from said original image by unsharpening said edge part using said edge information, said edge unsharpening part including a density information correction part for correcting density information of each pixel such that variation of density levels represented by density information of pixels which are arranged across said edge part in a near region of said edge part of said original image is lowered, said density information correction part including; a mean value calculation part for calculating a mean value of density levels in a predetermined region; and a density level judgment part for judging whether the density level of a pixel is higher or lower than said mean value for each pixel in said near region, wherein density information is corrected for a pixel in which said density level is higher than said mean value such that said density level is lowered, and density information is corrected for a pixel in which said density level is lower than said mean value such that said density level is increased; a first coding part for obtaining coded edge information by coding said edge information according to a first coding algorithm; a second coding part for obtaining coded density information by coding said density information of said edge unsharpened image according to a second coding algorithm; wherein said coded edge information and said coded density information are coded information of said original image, and wherein said second coding algorithm is based on a standard coding method using a discrete cosine transform. - View Dependent Claims (8, 9, 10, 11, 12)
-
-
13. An image decoding apparatus which decodes coded information which includes coded edge information obtained by coding edge information representing an edge part of an original image and coded density information representing an edge unsharpened image obtained by unsharpening said edge part of said original image using said edge information, said image decoding apparatus comprising:
-
a first decoding part for obtaining said edge information which is binary information representing said edge part by decoding said coded edge information according to a first decoding algorithm; a second decoding part for obtaining density information of said edge unsharpened image by decoding said coded density information according to a second decoding algorithm; an edge restoring part for restoring said edge part of said edge unsharpened image by using said edge information such that a reproduced image is obtained, said edge restoring part including a density information correction part for correcting density information of each pixel of said edge unsharpened image such that variation of density levels represented by density information of pixels which are arranged across said edge part in a near region of said edge part of said edge unsharpened image is increased, said density information correction part including; a mean value calculation part for calculating a mean value of density levels in a predetermined region; and a density level judgment part for judging whether the density level of a pixel is higher or lower than said mean value for each pixel in said near region, wherein density information is corrected for a pixel in which said density level is higher than said mean value such that said density level is increased, and density information is corrected for a pixel in which said density level is lower than said mean value such that said density level is lowered, wherein said second decoding algorithm is based on a standard coding method using a discrete cosine transform. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22)
-
-
23. An image decoding apparatus which decodes coded information of an image, said image decoding apparatus comprising:
-
an edge information obtaining part for obtaining edge information which is binary information representing an edge part of said image; a decoding part for obtaining density information of said image by decoding said coded information according to a predetermined decoding algorithm; an edge restoring part for restoring said edge part by using said edge information for said density information of said image such that a reproduced image is obtained, said edge restoring part including a density information correction part for correcting density information of each pixel of said edge unsharpened image such that variation of density levels represented by density information of pixels which are arranged across said edge part in a near region of said edge part of said edge unsharpened image is increased; a reference value calculation part for calculating a reference value of said density levels in a predetermined region; and a density level judgment part for judging whether said density level of a pixel is higher or lower than said reference value for each pixel in said near region, wherein density information is corrected for a pixel in which said density level is higher than said reference value such that said density level is increased, and density information is corrected for a pixel in which said density level is lower than said reference value such that said density level is lowered and wherein said predetermined decoding algorithm is based on a standard coding method using a discrete cosine transform. - View Dependent Claims (24)
-
Specification