Method and apparatus for compressing and expanding image data

Claim 2

A compression apparatus for compressing image data comprising: a reduced-image generating processor that transforms original image data partitioned into first blocks, each of which is composed of a plurality of pixels, to reduced-image data composed of a smaller number of pixels than that of said original image data; a fluency transform processor that applies a fluency transform to said reduced-image data to generate expanded-image data partitioned into second blocks corresponding to said first blocks, said fluency transform having a plurality of modes; a mode setting processor that selects one mode from said plurality of modes, said expanded-image data being generated in accordance with said selected one mode; an error calculating processor that calculates an error, which represents a difference between said original image data and said expanded-image data, said error calculating processor calculating said error in each of said plurality of modes; and an optimum mode determining processor that determines an optimum mode, by which said error becomes minimum, among said plurality of modes.

Claim 3

The compression apparatus according to claim 1 , further comprising a recording medium, said reduced-image data and said optimum mode being recorded in said recording medium.

Claim 4

The compression apparatus according to claim 1 , wherein each of said first blocks and each of said second blocks are composed of 8×8 (=64) pixels respectively.

Claim 5

The compression apparatus according to claim 1 , wherein said reduced-image generating processor generates said reduced-image data composed of average pixels, obtained by finding an average value of said plurality of pixels in each of said first blocks.

Claim 6

The compression apparatus according to claim 1 , wherein said fluency transform processor generates said expanded-image data by applying the fluency transform, which is expressed by the following formula, to each pixel of said reduced-image data: f  ( t ) = ( 1 / 2   π )  ∫ - π π  F  ( u ) [ m o ]   φ   ( t , u )   u note that, [ m o ]  φ  ( t , u ) =  ( 1 / 2   π )  ∫ - ∞ ∞  { ∑ p = - ∞ ∞   δ  ( ω - u + 2   π   p ) } ×  { ∑ q = - ∞ ∞   ( 1 - q  ( 2   π / ω ) ) - 2  m } - 1 / 2 × exp  (    ω   t )   ω where F(u) corresponds to each pixel value of said reduced-image data, f(t) is a output values of the fluency transform, φ (t,u) is the fluency function defined by a fluency function space m S, and m (=1,2,3, . . . ) is a parameter indicating a differentiability, said parameter m corresponding to said plurality of modes.

Claim 7

The compression apparatus according to claim 5 , wherein said fluency transform processor applies the fluency transform in a state such that each pixel of said reduced-image data are arranged at a center position of each of said second blocks, and generates said expanded-image data composed of said plurality of pixels by adding said output values f(t) corresponding to pixel-positions in said second blocks.

Claim 8

The compression apparatus according to claim 6 , wherein said plurality of pixels in said original image data is arranged in a matrix, and said fluency transform processor applies the fluency transform along a first direction to each pixel of said reduced-image data so that pixels aligned along said first direction are generated, and then applies the fluency transform to said pixels aligned along said first direction, along a second direction perpendicular to said first direction such that said plurality of pixels in each of said second blocks is generated.

Claim 9

The compression apparatus according to claim 1 , wherein said error calculating processor calculates a difference between each pixel value of said first blocks and each corresponding pixel value of said second blocks, and calculates a sum total of the square of said difference as said error, said optimum mode determining processor setting a mode, which makes said error minimum, among said plurality of modes as said optimum mode.

Claim 10

The compression apparatus according to claim 1 , wherein said optimum mode is determined in each of said second blocks.

Claim 11

An expansion apparatus for expanding said reduced-image data recorded in said recording medium by said compression apparatus in claim 2 , said expansion apparatus comprising: a data reading processor that reads said reduced-image data and said optimum mode recorded in said recording medium; an optimum mode setting processor that sets said optimum mode among said plurality of modes; and an expanded-image generating processor that applies said fluency transform based on said optimum mode to said reduced-image data such that expanded-image data corresponding to said original image data is obtained.

Claim 12

A compression method for compressing image data comprising: transforming original image data partitioned into first blocks, each of which is composed of a plurality of pixels, to reduced-image data composed of a smaller number of pixels than that of the original image data; applying a fluency transform to the reduced-image data to generate expanded-image data partitioned into second blocks corresponding to the first blocks, the fluency transform having a plurality of modes; selecting one mode from the plurality of modes, the expanded-image data being generated in accordance with the selected one mode; calculating an error in each of the plurality of modes, the error representing, a difference between the original image data and the expanded-image data; determining an optimum mode, by which the error becomes minimum, among the plurality of modes; and recording the reduced-image data and the optimum mode in a recording medium.

Claim 13

A compression method for compressing image data comprising: transforming original image data partitioned into first blocks, each of which is composed of a plurality of pixels, to reduced-image data composed of a smaller number of pixels than that of the original image data; applying a fluency transform to the reduced-image data to generate expanded-image data partitioned into second blocks corresponding to the first blocks, the fluency transform having a plurality of modes; selecting one mode from the plurality of modes, the expanded-image data being generated in accordance with the selected one mode; calculating an error in each of the plurality of modes, the error representing, a difference between the original image data and the expanded-image data; determining an optimum mode, by which the error becomes minimum, among the plurality of modes; and recording the reduced-image data and the optimum mode in a recording medium.

Claim 14

An expansion method for expanding said reduced-image data obtained by said compression method in claim 11 , said expansion method comprising: reading the reduced-image data and the optimum mode from the recording medium; setting the optimum mode among the plurality of modes; and applying the fluency transform based on said optimum mode to the reduced-image data such that expanded-image data corresponding to the original image data is obtained.

Claim 15

A memory medium that stores a program for compressing image data, the program comprising: transforming original image data partitioned into first blocks, each of which is composed of a plurality of pixels, to reduced-image data composed of a smaller number of pixels than that of the original image data; applying a fluency transform to the reduced-image data to generate expanded-image data partitioned into second blocks corresponding to the first blocks, the fluency transform having a plurality of modes; selecting one mode from the plurality of modes, the expanded-image data being generated in accordance with the selected one mode; calculating an error in each of the plurality of modes, the error representing, a difference between the original image data and the expanded-image data; determining an optimum mode, by which the error becomes minimum, among the plurality of modes; and recording the reduced-image data and the optimum mode in a recording medium.

Claim 16

A memory medium that stores a program for compressing image data, the program comprising: transforming original image data partitioned into first blocks, each of which is composed of a plurality of pixels, to reduced-image data composed of a smaller number of pixels than that of the original image data; applying a fluency transform to the reduced-image data to generate expanded-image data partitioned into second blocks corresponding to the first blocks, the fluency transform having a plurality of modes; selecting one mode from the plurality of modes, the expanded-image data being generated in accordance with the selected one mode; calculating an error in each of the plurality of modes, the error representing, a difference between the original image data and the expanded-image data; determining an optimum mode, by which the error becomes minimum, among the plurality of modes; and recording the reduced-image data and the optimum mode in a recording medium.

Claim 17

A memory medium that stores a program for expanding said reduced-image data described in claim 13 , comprising: reading the reduced-image data and the optimum mode from the recording medium; setting the optimum mode among the plurality of modes; and applying the fluency transform based on the optimum mode to the reduced-imaged data such that expanded image data corresponding to the original image data is obtained.

Claim 18

A compression apparatus for compressing image data comprising: a reduced-image generating processor that transforms original image data partitioned into first blocks, each of which is composed of a plurality of pixels, to reduced-image data composed of a smaller number of pixels than that of said original image data; a fluency transform processor that applies a fluency transform to said reduced-image data to generate expanded-image data partitioned into second blocks corresponding to said first blocks, said fluency transform having a plurality of modes; a contrast coefficient calculating processor that obtains a contrast coefficient in such a manner that a contrast of said expanded-image data becomes close to a contrast of said original image data by applying said contrast coefficient to said expanded-image data; a contrast transform processor that applies said contrast coefficient to said expanded-image data to modify the contrast of said expanded-image data so that modified expanded-image data is obtained; a mode setting processor that selects one mode from said plurality of modes, said modified expanded-image data being generated in accordance with said selected one mode; an error calculating processor that calculates an error, which represents a difference between said original image data and said modified expanded-image data, said error calculating processor calculating in each of said plurality of modes; and an optimum mode/contrast determining processor that determines an optimum mode, by which said error becomes minimum, among said plurality of modes, and then sets a contrast coefficient corresponding to said optimum mode as an optimum contrast coefficient.

Claim 19

A compression apparatus for compressing image data comprising: a reduced-image generating processor that transforms original image data partitioned into first blocks, each of which is composed of a plurality of pixels, to reduced-image data composed of a smaller number of pixels than that of said original image data; a fluency transform processor that applies a fluency transform to said reduced-image data to generate expanded-image data partitioned into second blocks corresponding to said first blocks, said fluency transform having a plurality of modes; a contrast coefficient calculating processor that obtains a contrast coefficient in such a manner that a contrast of said expanded-image data becomes close to a contrast of said original image data by applying said contrast coefficient to said expanded-image data; a contrast transform processor that applies said contrast coefficient to said expanded-image data to modify the contrast of said expanded-image data so that modified expanded-image data is obtained; a mode setting processor that selects one mode from said plurality of modes, said modified expanded-image data being generated in accordance with said selected one mode; an error calculating processor that calculates an error, which represents a difference between said original image data and said modified expanded-image data, said error calculating processor calculating in each of said plurality of modes; and an optimum mode/contrast determining processor that determines an optimum mode, by which said error becomes minimum, among said plurality of modes, and then sets a contrast coefficient corresponding to said optimum mode as an optimum contrast coefficient.

Claim 20

The compression apparatus according to claim 15 , wherein said contrast transform modifies said expanded-image data such that a pixel having a relatively high contrast in said expanded-image data is modified to a higher contrast pixel, and a pixel having a relatively low contrast in said expanded-image data is modified to a lower contrast pixel.

Claim 21

The compression apparatus according to claim 15 , wherein said contrast coefficient calculating processor obtains said contrast coefficient, which makes a sum of the square of the difference between each pixel value of said original image data and each corresponding pixel value of said modified expanded-image data.

Claim 22

The compression apparatus according to claim 15 , further comprising a recording medium, said optimum contrast coefficient and said optimum mode, said reduced-image data, said optimum contrast coefficient and said optimum mode being recorded in said recording medium.

Claim 23

An expansion apparatus for expanding said reduced-image data recorded in said recording medium by said compression apparatus for compressing the image data in claim 18 , said expansion apparatus comprising: a data reading processor that reads said reduced-image data, said optimum contrast coefficient and said optimum mode recorded in said recording medium; an optimum mode setting processor that sets said optimum mode among said plurality of modes; an expanded-image generating processor that applies said fluency transform according to said optimum mode to said reduced-image data such that expanded-image data corresponding to said original image data is obtained; and a contrast modifying processor that applies said contrast transform based on said optimum contrast coefficient to said expanded-image data, to obtain modified expanded-image data.