EP0258740A2 — Method of and apparatus for processing an image w…

Claim 1

Independent Claim 113 words

An image processing method of effecting an image processing on input video signals (11R, 11G, 11B) based on lookup table data to produce output signals CHARACTERIZED IN THAT said method comprises the steps of: receiving input video signals (11R, 11G, 11B) to establish highlight points and shadow points of the input video signals (11R, 11G, 11B); converting standard lookup table data into lookup table data associated with the input video signals (11R, 11G, 11B) based on the highlight points and the shadow points thus established; and effecting an image processing on the input video signals (11R, 11G, 11B) based on the lookup table data associated with the input video signals (11R, 11G, 11B).

Claim 2

Dependent Claim 113 words

An image processing method of effecting an image processing on input video signals (11R, 11G, 11B) based on lookup table data to produce output signals CHARACTERIZED IN THAT said method comprises the steps of: receiving input video signals (11R, 11G, 11B) to establish highlight points and shadow points of the input video signals (11R, 11G, 11B); converting standard lookup table data into lookup table data associated with the input video signals (11R, 11G, 11B) based on the highlight points and the shadow points thus established; and effecting an image processing on the input video signals (11R, 11G, 11B) based on the lookup table data associated with the input video signals (11R, 11G, 11B).

Claim 3

Dependent Claim 32 words

A method in accordance with claim 1, CHARACTERIZED IN THAT said image processing method is used in an image recording method which reproduces a visualized image on an image recording medium (30).

Claim 4

Dependent Claim 74 words

A method in accordance with claim 2, CHARACTERIZED IN THAT said image processing converts, based on the lookup table data, the input video signals (11R, 11G, 11B) by use of the lookup table data into signals representing an intensity of a light to be irradiated onto the image recording medium (30) and achieves a gradation correction on the input video signals (11R, 11G, 11B) depending on a shooting condition to produce a density signal.

Claim 5

Dependent Claim 39 words

A method in accordance with claim 1, CHARACTERIZED IN THAT said step for establishing the highlight points and the shadow points is accomplished based on cumulative histograms generated from the input video signals (11R, 11G, 11B) in said step.

Claim 6

Dependent Claim 82 words

A method in accordance with claim 1, CHARACTERIZED IN THAT said conversion of the lookup table data is conducted by converting the standard lookup table data L0 through a functional transformation represented by and expression L(v) = S[c L0{a(v+b)} + d] to attain lookup table data L(v) associated with the input video signals (11R, 11G, 11B) in which parameters a, b, c and d are determined by passing the function represented by the expression through the highlight points and the shadow points.

Claim 7

Dependent Claim 28 words

A method in accordance with claim 1, CHARACTERIZED IN THAT said standard lookup table data is a video gamma curve represented by an expression D = -2.2Log v.

Claim 8

Dependent Claim 43 words

A method in accordance with claim 4, CHARACTERIZED IN THAT said step for establishing the highlight points and the shadow points sets at least one of the highlight points and the shadow points based on at least two points on the cumulative histograms.

Claim 9

Dependent Claim 61 words

A method in accordance with claim 7, CHARACTERIZED IN THAT said step for establishing the highlight points and the shadow points calculates the highlight point CH from an expression CH = C2(C2-C3)/(C1-C3) + C1(C1-C2)/(C1-C3) in which C1, C2 and C3 respectively represent input video signal levels at points of frequencies 99 %, 95 % and 90 % in the cumulative histograms.

Claim 10

Dependent Claim 33 words

A method in accordance with claim 8, CHARACTERIZED IN THAT the values of said (C2-C3)/(C1-C3) and (C1-C2)/(C1-C3) each are 1/2 and the highlight point CH is calculated from an expression CH = 1/2(C2+C1).

Claim 11

Dependent Claim 82 words

A method in accordance with claim 4, CHARACTERIZED IN THAT said method further comprises the step of: an input signal level change buffer processing for minimizing a change in a signal level of the input video signals (11R, 11G, 11B), wherein the step for establishing the highlight points and the shadow points is achieved based on the input video signals (39R, 39G, 39B) for which the change in the signal level is reduced in the input signal level change buffer processing step.

Claim 12

Dependent Claim 52 words

A method in accordance with claim 10, CHARACTERIZED IN THAT said input signal level change buffer processing step uses sharpness circuits (40R, 40G, 40B) to change sharpness coefficients set to the sharpness circuits (40R, 40G, 40B), thereby smoothing the change in the signal level of the input video signals (11R, 11G, 11B).

Claim 13

Dependent Claim 26 words

A method in accordance with claim 10, CHARACTERIZED IN THAT said input signal level change buffer processing step is effected by use of a low-pass filter.

Claim 14

Dependent Claim 40 words

A method in accordance with claim 10, CHARACTERIZED IN THAT said input signal level change buffer processing step reduces the change in the signal level only for a luminance signal (41) included in the input video signals (11R, 11G, 11B).

Claim 15

Dependent Claim 86 words

A method in accordance with claim 4, CHARACTERIZED IN THAT said method further comprises the step of: receiving the input video signals (11R, 11G, 11B) to effect a color correction level adjustment on the input video signals (11R, 11G, 11B), thereby producing output signals (43R, 43G, 43B), wherein said step for establishing the highlight points and the shadow points is accomplished based on the signals (43R, 43G, 43B) for which the color correction level adjustment is effected in said color correction level adjusted signal generating step.

Claim 16

Dependent Claim 65 words

A method in accordance with claim 14, CHARACTERIZED IN THAT said color correction level adjusted signal generating step is conducted on each chroma signal of the input video signals (11R, 11G, 11B) in consideration of a value of a signal representing a brightness of the input video signals (11R, 11G, 11B) in which the color correction level adjustment can be set to a desired degree.

Claim 17

Dependent Claim 82 words

A method in accordance with claim 15, CHARACTERIZED IN THAT said color correction level adjusted signal generating step is conducted on each chroma signal C of the input video signals (11R, 11G, 11B) in consideration of a luminance signal Y of the input video signals (11R, 11G, 11B) to achieve the color correction level adjustment according to an expression Cʹ = kC + (1-k)Y in which the value of k is changed to control the degree of the color correction level adjustment.

Claim 18

Dependent Claim 32 words

A method in accordance with claim 16, CHARACTERIZED IN THAT said color correction level adjusted signal generating step enables an operator to set the value of k through checking a corrected image.

Claim 19

Dependent Claim 46 words

A method in accordance with claim 17, CHARACTERIZED IN THAT said value of k is beforehand set to 1 so that when the operator confirms that a highlight white does not exist in the corrected image, the value of k is changed to a small value.

Claim 20

Dependent Claim 26 words

A method in accordance with claim 16, CHARACTERIZED IN THAT said value of k is beforehand set to a substantially middle point between 1 and 0.

Claim 21

Dependent Claim 71 words

A method in accordance with claim 15, CHARACTERIZED IN THAT said color correction level adjusted signal generating step is conducted on each chroma signal of R, G and B of the input video signals (11R, 11G, 11B) in consideration of a value of a signal 1/3(R+G+B) representing a brightness of the input video signals (11R, 11G, 11B) in which the color correction level adjustment can be set to a desired degree.

Claim 22

Dependent Claim 137 words

An image processing apparatus CHARACTERIZED IN THAT said apparatus comprises: image processing means (14R, 14G, 14B) for effecting an image processing on input video signals (11R, 11G, 11B) based on lookup table data to produce output signals; highlight point and shadow point establishing means (32R, 32G, 32B) for receiving the input video signals (11R, 11G, 11B) to set highlight points and shadow points each of the input video signals (11R, 11G, 11B); standard lookup table keeping means (36) for keeping standard lookup table data; lookup table converting means (34R, 34G, 34B) for converting the standard lookup table data, based on the highlight points and the shadow points thus established, into lookup table data associated with the input video signals (11R, 11G, 11B) to deliver the obtained lookup table data to the image processing means (14R, 14G, 14B).

Claim 23

Dependent Claim 137 words

An image processing apparatus CHARACTERIZED IN THAT said apparatus comprises: image processing means (14R, 14G, 14B) for effecting an image processing on input video signals (11R, 11G, 11B) based on lookup table data to produce output signals; highlight point and shadow point establishing means (32R, 32G, 32B) for receiving the input video signals (11R, 11G, 11B) to set highlight points and shadow points each of the input video signals (11R, 11G, 11B); standard lookup table keeping means (36) for keeping standard lookup table data; lookup table converting means (34R, 34G, 34B) for converting the standard lookup table data, based on the highlight points and the shadow points thus established, into lookup table data associated with the input video signals (11R, 11G, 11B) to deliver the obtained lookup table data to the image processing means (14R, 14G, 14B).

Claim 24

Dependent Claim 35 words

An apparatus in accordance with claim 21, CHARACTERIZED IN THAT said image processing means (14R, 14G, 14B) are used in an image recording system which reproduces a visualized image on an image recording medium (30).

Claim 25

Dependent Claim 77 words

An apparatus in accordance with claim 22, CHARACTERIZED IN THAT said image processing means (14R, 14G, 14B) include gradation correcting means storing the lookup table data to convert the input video signals, by use of the gradation correcting means, into a signal representing an intensity of a light to be irradiated on to the image recording medium and conducts a gradation correction on the input video signals according to a shooting condition, thereby producing a density signal.

Claim 26

Dependent Claim 64 words

An apparatus in accordance with claim 21, CHARACTERIZED IN THAT said highlight point and shadow point establishing means (32R, 32G, 32B) include cumulative histogram generating means (32R, 32G, 32B) generating cumulative histograms from the input video signals (11R, 11G, 11B) to establish the highlight points and the shadow points based on the cumulative histograms generated by said cumulative histogram generating means (32R, 32G, 32B).

Claim 27

Dependent Claim 80 words

An apparatus in accordance with claim 21, CHARACTERIZED IN THAT said lookup table converting means (34R, 34G, 34B) convert the standard lookup table data L0 through a functional transformation represented by an expression L(v) = S[c L0{a(v+b)} + d] to attain lookup table data L(v) associated with the input video signals (11R, 11G, 11B) in which parameters a, b, c and d are determined by passing the function represented by the expression through the highlight points and the shadow points.

Claim 28

Dependent Claim 28 words

An apparatus in accordance with claim 21, CHARACTERIZED IN THAT said standard lookup table data is a video gamma curve represented by an expression D = -2.2Log v.

Claim 29

Dependent Claim 42 words

An apparatus in accordance with claim 24, CHARACTERIZED IN THAT said highlight point and shadow point establishing means (32R, 32G, 32B) set at least either the highlight points or the shadow points based on at least two points on the cumulative histograms.

Claim 30

Dependent Claim 61 words

An apparatus in accordance with claim 27, CHARACTERIZED IN THAT said highlight point and shadow point establishing means (32R, 32G, 32B) calculate the highlight point CH from an expression CH = C2(C2-C3)/(C1-C3) + C1(C1-C2)/(C1-C3) in which C1, C2 and C2 respectively represent input video signal levels at points of frequencies 99 %, 95 % and 90 % in the cumulative histograms.

Claim 31

Dependent Claim 30 words

An apparatus in accordance with claim 28, CHARACTERIZED IN THAT said (C2-C3)/(C1-C3) and (C1-C2)/(C1-C3) each are 1/2 and the highlight point CH is calculated from an expression CH = 1/2(C2+C1).

Claim 32

Dependent Claim 91 words

An apparatus in accordance with claim 24, CHARACTERIZED IN THAT said apparatus further comprises input signal level change buffer processing means (40R, 40G, 40B) for minimizing a change in a signal level of the input video signals (11R, 11G, 11B) wherein said highlight point and shadow point establishing means (32R, 32G, 32B) set the highlight points and the shadow points based on the input video signals (39R, 39G, 39B) for which the change in the signal level is reduced by said input signal level change buffer processing means (40R, 40G, 40B).

Claim 33

Dependent Claim 53 words

An apparatus in accordance with claim 30, CHARACTERIZED IN THAT said input signal level change buffer processing means (40R, 40G, 40B) include sharpness circuits (40R, 40G, 40B) loaded with variable sharpness coefficients, said sharpness circuit being capable of smoothing the change in the signal level of the input video signals (11R, 11G, 11B).

Claim 34

Dependent Claim 24 words

An apparatus in accordance with claim 30, CHARACTERIZED IN THAT said input signal level change buffer processing means (40R, 40G, 40B) are low-pass filters.

Claim 35

Dependent Claim 54 words

An apparatus in accordance with claim 30, CHARACTERIZED IN THAT said input signal level change buffer processing means (40R, 40G, 40B) effect processing to reduce the change in signal level only for a luminance signal included in the input video signals (11R, 11G, 11B) inputted to the cumulative histogram generating means (32R, 32G, 32B).

Claim 36

Dependent Claim 96 words

A method in accordance with claim 24, CHARACTERIZED IN THAT said apparatus further comprises color correction level adjusting means (44) for receiving the input video signals (11R, 11G, 11B) to effect a color correction level adjustment on the input video signals (11R, 11G, 11B), thereby producing output signals (43R, 43G, 43B), wherein said highlight point and the shadow point establishing means (32R, 32G, 32B) set the highlight points and the shadow points based on the signals (43R, 43G, 43B) for which the color correction level adjustment is effected in said color correction level adjusting means (44).

Claim 37

Dependent Claim 68 words

An apparatus in accordance with claim 34, CHARACTERIZED IN THAT said color correction level adjusting means (44) effects the color correction level adjustment on each chroma signal of the input video signals (11R, 11G, 11B) in consideration of a value of a signal representing a brightness of the input video signals (11R, 11G, 11B) in which the color correction level adjustment can be set to a desired degree.

Claim 38

Dependent Claim 78 words

An apparatus in accordance with claim 35, CHARACTERIZED IN THAT said color correction level adjusting means (44) effects the color correction level adjustment on each chroma signal C of the input video signals (11R, 11G, 11B) in consideration of a luminance signal Y of the input video signals (11R, 11G, 11B) according to an expression Cʹ = kC + (1-k)Y in which the value of k is changed to control the degree of the color correction level adjustment.

Claim 39

Dependent Claim 48 words

An apparatus in accordance with claim 36, CHARACTERIZED IN THAT said color correction level adjusting means (44) enables an operator to set the value of k to be used for the color correction level adjustment through checking an image corrected by said gradation correcting means (14R, 14G, 14B).

Claim 40

Dependent Claim 54 words

An apparatus in accordance with claim 37, CHARACTERIZED IN THAT said value of k is beforehand set to 1 so that when the operator confirms that a highlight white does not exist in the image corrected by said gradation correcting means (14R, 14G, 14B), the value of k is changed to a small value.

Claim 41

Dependent Claim 25 words

An apparatus in accordance with claim 36, CHARACTERIZED IN THAT said value of k is set to a substantially middle point between 1 and 0.

Claim 42

Dependent Claim 71 words

An apparatus in accordance with claim 35, CHARACTERIZED IN THAT said color correction level adjusting means (44) conducts the color correction level adjustment on each chroma signal of R, G and B of the input video signals (11R, 11G, 11B) in consideration of a value of a signal 1/3(R+G+B) representing a brightness of the input video signals in which the color correction level adjustment can be set to a desired degree.

Method of and apparatus for processing an image with gradation correction of video signal

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