US 7,031,516 B2 · Edge achromatization circuit and method

Abstract

An edge achromatization circuit and method is disclosed wherein, in digital camera signal processing, a signal having a linear characteristic before γ correction is performed to suppress a color component of an edge portion while keeping a luminance. The edge achromatization circuit includes a luminance signal operation matrix circuit for converting R, G, B signals before γ correction is performed therefor into a luminance signal, an edge detection circuit for extracting an edge signal from the luminance signal, an absolute value operation circuit for converting the edge signal into an absolute value, a multiplier for controlling the gain of the absolute value, subtractors for obtaining color difference signals from the R, G, B signals and the luminance signal, multipliers for multiplying the color difference signals and an output coefficient, and subtractors for arithmetically operating results of the multiplication and the R, G, B signals to obtain R′, G′, B′ color signals. The edge achromatization circuit can perform achromatization of an edge of an image without providing a quick variation to the signal.

Claims14

Dependent claims

An edge achromatization circuit, comprising:

luminance signal conversion means for converting first color signals inputted from an input terminal group before γ correction processing into a luminance signal;
first subtraction means for arithmetically operating the luminance signal and the first color signals to obtain color difference signals;
edge detection means for detecting an edge signal from the luminance signal;
absolute value operation means for converting the edge signal into an absolute value;
first multiplication means for multiplying the absolute from said absolute value operation means and a first coefficient signal inputted thereto from said input terminal group to control the gain of the value;
level limit means for obtaining a second output coefficient from the value of the controlled gain and a limit level setting signal inputted thereto from said input terminal group;
second multiplication means for multiplying the second output coefficient and the color difference signals outputted from said first subtraction means;
and
second subtraction means for arithmetically operating results of the multiplication by said second multiplication means and the first color signals to obtain second color signals to be outputted from said edge achromatization circuit.

6 more elements

An edge achromatization circuit, comprising:

switching means for switchably outputting first color signals inputted from an input terminal group before γ correction processing and second color signals;
luminance signal conversion means for converting the first color signals or the second color signals switchably inputted thereto from said switching means into a luminance signal;
first subtraction means for arithmetically operating the luminance signal and the first color signals or the second color signals switchably inputted thereto from said switching means to obtain color difference signals;
first sample hold means for extracting the color difference signals obtained by said first subtraction means;
second sample hold means for extracting the luminance signal outputted from said luminance signal conversion means;
edge detection means for detecting an edge signal from the luminance signal extracted by said second sample hold means;
absolute value operation means for converting the edge signal into an absolute value;
first multiplication means for multiplying the absolute value from said absolute value operation means and a first coefficient signal inputted thereto from said input terminal group to control the gain of the value;
level limit means for obtaining a second output coefficient from the value of the control gain and a limit level setting signal inputted thereto from said input terminal group;
second multiplication means for multiplying the second output coefficient and the color difference signals extracted by said first sample hold means;
second subtraction means for arithmetically operating results of the multiplication by said second multiplication means and the first color signals or the second color signals switchably inputted from said switching means to obtain third color signals,
third sample hold means for extracting color difference signals from the outputs of said first sample hold means;
and
fourth sample hold means for extracting a luminance signal component from the output of said second sample hold means.

11 more elements

An edge achromatization circuit, comprising

first to fifth input terminals, luminance signal operation means, first to sixth subtraction means, first to fourth multiplication means, edge detection means, absolute value operation means, level limit means, and first to third output terminals;
said first to third input terminals being connected to an R signal input, a G signal input and a B signal input of said luminance signal operation means, minuend inputs of said first to third subtraction means and minuend inputs of said fourth to sixth subtraction means, respectively;
an output of said luminance signal operation means being connected to the minuend inputs of said first to third subtraction means and an input of said edge detection means;
outputs of said first to third subtraction means being inputted to first inputs of said first to third multiplication means, respectively;
an output of said edge detection means being connected to an input of said absolute value operation means;
an output of said absolute value operation means being connected to a first input of said fourth multiplication means;
said fourth input terminal being connected to a second input of said fourth multiplication means;
an output of said fourth multiplication means being connected to an input of said level limit means;
said fifth input terminal being connected to a limit level input of said level limit means;
an output of said level limit means being connected to second inputs of said first to third multiplication means;
outputs of said first to third multiplication means being connected to subtrahend inputs of said fourth to sixth subtraction means, respectively;
outputs of said fourth to sixth subtraction means being connected to said first to third output terminals, respectively.

9 more elements

An edge achromatization circuit, comprising:

first to fifth input terminals, luminance signal conversion means, first to sixth subtraction means, first to fourth multiplication means, edge detection means, absolute value operation means, level limit means, first to third 2-input switch means, first to eighth sample hold means, and first to seventh output terminals;
said first to third 2-input switch means having first input terminals to which first color signals from said first to third input terminals are inputted and second input terminals to which second color signals from said fourth to sixth subtraction means are inputted, respectively;
outputs of said first to third 2-input switch means alternately outputting the first color signals and the second color signals to said luminance signal conversion means and said first to third subtraction means, respectively;
said luminance signal conversion means alternately outputting a first luminance signal obtained by conversion from the first color signals and a second luminance signal obtained by conversion from the second color signals to said first to third subtraction means and said fourth sample hold means;
said first to third subtraction means arithmetically operating the first color signals and the first luminance signal or the second color signals and the second luminance signal to produce first color difference signals or second color difference signals to be outputted to said first to third sample hold means;
said fourth sample hold means outputting the luminance signal outputted from said luminance signal conversion means to said edge detection means and said eighth sample hold means;
said edge detection means detecting an edge signal from the luminance signal and outputting the edge signal to said absolute value operation means;
said absolute value operation means converting the edge signal into an absolute value and outputting the absolute value to said first multiplication means;
said first multiplication means outputting a value obtained by arithmetic operation of the absolute value from said absolute value operation means and a first output coefficient inputted from said fourth input terminal to said level limit means;
said level limit means calculating a second output coefficient from the value from said first multiplication means and a level limit setting signal inputted thereto from said fifth input terminal and outputting the second output coefficient to said second to fourth multiplication means;
said second to fourth multiplication means arithmetically operating the second output coefficient and the first color difference signals or the second color difference signals outputted from said first to third sample hold means and outputting results of the arithmetic operation to said fourth to sixth subtraction means, respectively;
said fourth to sixth subtraction means arithmetically operating the outputs of said second to fourth multiplication means and the first color signals or the second color signals to produce third color signals and outputting the third color signals to said first to third output terminals, respectively;
said fifth to seventh sample hold means extracting color difference signals from the outputs of said second to fourth sample hold means and outputting the color difference signals to said fifth to seventh output terminals, respectively,
said eighth sample hold means extracting a luminance signal component from the output of said fourth sample hold means and outputting the luminance signal component to said fourth output terminal.

11 more elements

An edge achromatization method for an edge achromatization apparatus, comprising:

a switching step of switchably outputting first color signals inputted from an input terminal group of said edge achromatization apparatus before γ correction processing and second color signals;
a luminance signal conversion step of converting the first color signals or the second color signals switchably inputted by the switching step into a luminance signal;
a first subtraction step of arithmetically operating the luminance signal and the first color signals or the second color signals switchably inputted by the switching step to obtain color difference signals;
a first sample hold step of extracting the color difference signals obtained by the first subtraction step;
a second sample hold step of extracting the luminance signal outputted by the luminance signal conversion step;
an edge detection step of detecting an edge signal from the luminance signal extracted by the first sample hold step;
an absolute value operation step of converting the edge signal into an absolute value;
a first multiplication step of multiplying the absolute value and a first coefficient signal inputted from said input terminal group to adjust the gain of the value;
a level limit step of obtaining a second output coefficient from the value of the controlled gain and a limit level setting signal inputted from said input terminal group;
a second multiplication step of multiplying the second output coefficient and the color difference signals extracted by the first sample hold step;
a second subtraction step of arithmetically operating results of the multiplication by the second multiplication step and the first color signals or the second color signals switchably inputted by the switching step to obtain third color signals;
a third sample hold step of extracting color difference signals from the outputs of the first sample hold step;
and
a fourth sample hold step of extracting a luminance signal component from the output of the second sample hold step.

11 more elements

Dependencies are inferred from the claim text.

Edge achromatization circuit and method

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Edge achromatization circuit and method

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Abstract

Claims14