WO2015115866A1 - Procédé et appareil d'interpolation du signal de couleur d'une image - Google Patents

Procédé et appareil d'interpolation du signal de couleur d'une image Download PDF

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WO2015115866A1
WO2015115866A1 PCT/KR2015/001061 KR2015001061W WO2015115866A1 WO 2015115866 A1 WO2015115866 A1 WO 2015115866A1 KR 2015001061 W KR2015001061 W KR 2015001061W WO 2015115866 A1 WO2015115866 A1 WO 2015115866A1
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signal
color
difference value
difference
pixels
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PCT/KR2015/001061
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English (en)
Korean (ko)
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태용민
이성원
문영수
조정욱
김도형
이시화
이정훈
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삼성전자 주식회사
광운대학교 산학협력단
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Publication of WO2015115866A1 publication Critical patent/WO2015115866A1/fr

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N9/00—Details of colour television systems
    • H04N9/64—Circuits for processing colour signals
    • H04N9/646—Circuits for processing colour signals for image enhancement, e.g. vertical detail restoration, cross-colour elimination, contour correction, chrominance trapping filters
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T3/00—Geometric image transformations in the plane of the image
    • G06T3/40—Scaling of whole images or parts thereof, e.g. expanding or contracting
    • G06T3/4015—Image demosaicing, e.g. colour filter arrays [CFA] or Bayer patterns
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/46—Colour picture communication systems
    • H04N1/56—Processing of colour picture signals
    • H04N1/60—Colour correction or control
    • H04N1/603—Colour correction or control controlled by characteristics of the picture signal generator or the picture reproducer
    • H04N1/6033—Colour correction or control controlled by characteristics of the picture signal generator or the picture reproducer using test pattern analysis
    • H04N1/6044—Colour correction or control controlled by characteristics of the picture signal generator or the picture reproducer using test pattern analysis involving a sensor integrated in the machine or otherwise specifically adapted to read the test pattern
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/46—Measurement of colour; Colour measuring devices, e.g. colorimeters
    • G01J2003/467—Colour computing
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N2209/00—Details of colour television systems
    • H04N2209/04—Picture signal generators
    • H04N2209/041—Picture signal generators using solid-state devices
    • H04N2209/042—Picture signal generators using solid-state devices having a single pick-up sensor
    • H04N2209/045—Picture signal generators using solid-state devices having a single pick-up sensor using mosaic colour filter
    • H04N2209/046—Colour interpolation to calculate the missing colour values

Definitions

  • a method, apparatus and recording medium for interpolating a color signal of an image is a method, apparatus and recording medium for interpolating a color signal of an image.
  • the ISP Image Signal Processor
  • RGB data YUV data
  • YCbCr data YCbCr data based on the raw image of an image obtained by photographing a subject from a digital image input device such as a digital camera or a smart phone. can do.
  • the ISP includes various image signal processing functional blocks for processing raw images. Examples include functional blocks such as White Balance, Color Interpolation, Noise Reduction, Edge Enhancement, Gamma Correction, Color Correction, etc. do.
  • the color interpolation module plays an important role in image quality, and there are many algorithms for color interpolation. Among them, the Adaptive Homogeneity-directed Demosaicing (AHD) color interpolation method interpolates colors using a homogeneity map.
  • AHD Adaptive Homogeneity-directed Demosaicing
  • the disclosed embodiments aim to reduce the amount of computation performed to interpolate the color signal of an image by providing information for obtaining the difference in the luminance signal and the difference in the color difference signal without converting the color space based on the difference in the color signal.
  • a method of interpolating a color signal of an image may include generating horizontal interpolation data and vertical interpolation data based on a result of interpolating a color signal of an image for each channel; Obtaining a difference value of a color signal between a target pixel and a pixel corresponding to the comparison pixel adjacent to the target pixel from the horizontal interpolation data and the vertical interpolation data; Obtaining a luminance signal difference value and a color difference signal difference value between pixels corresponding to the target pixel and the comparison pixel, respectively, based on the difference values of the color signals respectively obtained from the horizontal interpolation data and the vertical interpolation data; And comparing the first luminance signal difference value and the first color difference signal difference value obtained from the horizontal interpolation data with the second luminance signal difference value and the second color difference signal difference value obtained from the vertical interpolation data, respectively, Determining an interpolation direction of the luminance signal and an interpolation direction of the chrominance signal.
  • the amount of computation performed in the process of interpolating the color signal of the image can be significantly reduced.
  • FIG. 1 is a diagram illustrating a system for demosaicing an image based on an Adaptive Homogeneity-directed Demosaicing (AHD) algorithm according to an embodiment of the present invention.
  • AHD Adaptive Homogeneity-directed Demosaicing
  • FIG. 2 is a flowchart illustrating a method of interpolating a color signal of an image according to an embodiment of the present invention.
  • FIG. 3 is a flowchart illustrating a method of obtaining a luminance signal difference value and a color difference signal difference value based on a channel signal difference value between a target pixel included in an image and a comparison pixel according to an exemplary embodiment of the present invention.
  • FIG. 4 is a flowchart illustrating a method of determining in detail a difference value of a luminance signal corresponding to a difference value of a color signal between pixels and a difference value of a color difference signal according to an embodiment of the present invention.
  • FIG. 5 is a diagram for describing each pixel corresponding to a target pixel and a comparison pixel adjacent to the target pixel in the horizontal interpolation data and the vertical interpolation data according to an embodiment of the present invention.
  • FIG. 6 is a flowchart illustrating a method of determining homogeneity parameters of luminance signals and homogeneity parameters of color difference signals, according to an embodiment of the present invention.
  • FIG. 7 and 8 are block diagrams of an apparatus for interpolating color signals of an image according to an embodiment of the present invention.
  • a method of interpolating a color signal of an image may include generating horizontal interpolation data and vertical interpolation data based on a result of interpolating a color signal of an image for each channel; Obtaining a difference value of a color signal between a target pixel and a pixel corresponding to the comparison pixel adjacent to the target pixel from the horizontal interpolation data and the vertical interpolation data; Obtaining a luminance signal difference value and a color difference signal difference value between pixels corresponding to the target pixel and the comparison pixel, respectively, based on the difference values of the color signals respectively obtained from the horizontal interpolation data and the vertical interpolation data; And comparing the first luminance signal difference value and the first color difference signal difference value obtained from the horizontal interpolation data with the second luminance signal difference value and the second color difference signal difference value obtained from the vertical interpolation data, respectively, Determining an interpolation direction of the luminance signal and an interpolation direction of the chrominance signal.
  • the obtaining of the luminance signal difference value and the color difference signal difference value may include: obtaining a color signal obtained from the horizontal interpolation data and the vertical interpolation data. Comparing the difference value with preset conversion condition information; And a difference value between the first luminance signal corresponding to the difference value of the color signal obtained from the horizontal interpolation data and the difference value between the first color difference signal and the color signal obtained from the vertical interpolation data, based on the comparison result.
  • the conversion condition information includes a difference value of the luminance signal corresponding to the difference value of the color signal between the pixels and the color difference signal. Characterized in that it contains information about the difference value of.
  • the conversion condition information is generated based on a result of converting a color signal of an RGB color space into a color difference signal and a luminance signal of a YCgCo color space. It is characterized by.
  • the method of interpolating a color signal of an image according to an embodiment of the present invention further includes generating conversion condition information including a luminance difference value and a color difference difference value corresponding to the color difference value between pixels.
  • the determining of the interpolation direction may include pixels corresponding to the target pixel and comparison pixels positioned at upper and lower ends of the target pixel, respectively.
  • the luminance signal difference value and the chrominance signal difference value between the pixels other than the compared pixels are determined.
  • the number of pixels having a luminance signal difference smaller than the homogeneity parameter of the luminance signal and the color difference signal difference smaller than the homogeneity parameter of the chrominance signal based on the result of the compared pixels and the comparison result of the remaining pixels Determining a number of pixels having a value; And determining the interpolation direction of the luminance signal of the target pixel and the interpolation direction of the chrominance signal of the target pixel based on the number of pixels respectively determined for the luminance signal and the chrominance signal of the target pixel.
  • the determining of the homogeneity parameter of the luminance signal and the homogeneity parameter of the chrominance signal may include storing information on the pre-compared pixels. And comparing the luminance signal difference value and the color difference signal difference value between the remaining pixels with the homogeneity parameter of the luminance signal and the homogeneity parameter of the color difference signal, based on the information about the stored pre-compared pixels. Extracting preset comparison target pixel information; And acquiring information on the remaining pixels based on the extracted comparison object pixel information.
  • the generating of the horizontal interpolation data and the vertical interpolation data may be performed based on a result of interpolating the color signals of the image for each channel, in a horizontal direction.
  • An apparatus for interpolating a color signal of an image generates horizontal interpolation data and vertical interpolation data based on a result of interpolating a color signal of an image for each channel, and generates a target pixel and the target pixel.
  • a color signal obtaining unit obtaining a difference value of a color signal between pixels corresponding to adjacent comparison pixels from the horizontal interpolation data and the vertical interpolation data;
  • a signal converter configured to obtain a luminance signal difference value and a color difference signal difference value between pixels corresponding to the target pixel and the comparison pixel based on difference values of color signals respectively obtained from the horizontal interpolation data and the vertical interpolation data ; And comparing the first luminance signal difference value and the first color difference signal difference value obtained from the horizontal interpolation data with the second luminance signal difference value and the second color difference signal difference value obtained from the vertical interpolation data, respectively, And a determining section for determining the interpolation direction of the luminance signal and the interpolation direction of the chrominance signal.
  • the signal converter is configured to compare the difference value of the color signal obtained from the horizontal interpolation data and the vertical interpolation data with preset conversion condition information.
  • a conversion condition comparison unit And a difference value between the first luminance signal corresponding to the difference value of the color signal obtained from the horizontal interpolation data and the difference value between the first color difference signal and the color signal obtained from the vertical interpolation data, based on the comparison result.
  • a difference value determiner that determines a difference value of the second luminance signal corresponding to the value and a difference value of the second color difference signal, and the conversion condition information includes a difference value and a color difference of the luminance signal corresponding to the difference value of the color signal between pixels. Characterized in that the information on the difference value of the signal.
  • the conversion condition information is generated based on a result of converting a color signal of an RGB color space into a color difference signal and a luminance signal of a YCgCo color space. It is characterized by.
  • the signal conversion unit In the apparatus for interpolating a color signal of an image according to an embodiment of the present invention, the signal conversion unit generates conversion condition information including a luminance difference value and a color difference difference value corresponding to the color difference value between pixels. do.
  • the determining unit the first luminance signal between the pixels corresponding to each of the target pixel and the comparison pixels located at the top and bottom of the target pixel, respectively.
  • the difference between the first color difference signal and the second color difference signal difference between the magnitude of the difference value and the second luminance signal difference value and the pixels corresponding to the target pixels and the comparison pixels positioned on the left and right sides of the target pixel.
  • a parameter determining unit that determines homogeneity parameters of the luminance signal and homogeneity parameters of the chrominance signal based on the magnitudes; In the process of determining the homogeneity parameter of the luminance signal and the homogeneity parameter of the chrominance signal, the luminance signal difference value and the chrominance signal difference value between the pixels other than the compared pixels are compared to the homogeneity parameter of the luminance signal and the homogeneity of the color difference signal.
  • a number of pixels having a luminance signal difference less than the homogeneity parameter of the luminance signal and a homogeneity parameter of the chrominance signal based on a comparison with a parameter and a result for the pre-compared pixels and a comparison result for the remaining pixels.
  • a homogeneity determination unit that determines the number of pixels having a smaller color difference signal difference value; And an interpolation direction determiner configured to determine an interpolation direction of the luminance signal of the target pixel and an interpolation direction of the color difference signal of the target pixel based on the number of pixels respectively determined for the luminance signal and the chrominance signal of the target pixel. It features.
  • the parameter determiner stores information on the pre-compare pixels, and the homogeneity determiner is configured to store the pre-compared pixels. And extracting preset comparison target pixel information based on the received information, and obtaining information on the remaining pixels based on the extracted comparison target pixel information.
  • the color signal acquisition unit based on a result of interpolating the color signal of the image for each channel, of the at least one channel interpolated in the horizontal direction And horizontal interpolation data including color signals and vertical interpolation data including color signals of at least one channel interpolated in the vertical direction.
  • FIG. 1 is a diagram illustrating a system 100 for demosaicing an image based on an Adaptive Homogeneity-directed Demosaicing (AHD) algorithm in accordance with an embodiment of the present invention.
  • AHD Adaptive Homogeneity-directed Demosaicing
  • a system 100 for demosaicing an image based on an AHD algorithm may include an image acquirer 110, a horizontal interpolator 120, a vertical interpolator 130, and a color space converter 140.
  • the parameter determiner 150 and the homogeneity map generator 160 may be included.
  • the image acquirer 110 may obtain raw data obtained by digitizing an electrical signal generated by the image capturing apparatus.
  • the semiconductor device may include a semiconductor device that generates light corresponding to the subject of the image photographing apparatus as an electric signal.
  • a CCD sensor or a CMOS sensor may be included in the image capturing apparatus.
  • the raw signal acquired by the image acquirer 110 includes one color signal in one pixel.
  • the process of correcting one color signal present in one pixel to three full colors is a demosaicing process.
  • FIG. 1 describes the demosaicing process using the AHD algorithm.
  • a homogeneity map can be generated to confirm homogeneity in two directions, horizontal and vertical.
  • the horizontal interpolator 120 and the vertical interpolator 130 may interpolate the acquired image in the horizontal direction and interpolate in the vertical direction.
  • the horizontal interpolator 120 and the vertical interpolator 130 may interpolate color signals of at least one channel among the three color signals included in the image in the horizontal direction and the vertical direction, respectively.
  • the color space converter 140 may convert the color space of the horizontal interpolation data generated as a result of horizontal interpolation of the image by the horizontal interpolation unit 120 and the vertical interpolation data obtained by vertical interpolation of the image at the vertical interpolation unit 130.
  • the general AHD algorithm performs CIELab conversion on the color signal of the RGB channel. In the process of performing CIELab conversion on the color signal of the RGB channel, the cube operation used has a problem of increasing the amount of computation in demosaicing using the AHD algorithm.
  • the parameter determiner 150 may further include parameters for the luminance signal for each pixel constituting the image based on the luminance signal and the color difference signal of the image converted from the horizontal interpolation data and the luminance signal and the color difference signal of the image converted from the vertical interpolation data. Parameters for the chrominance signal may be determined. The parameter for the luminance signal and the parameter for the chrominance signal determined by the parameter determiner become a reference for determining the interpolation direction of the target pixel.
  • the homogeneity map generator 160 compares the luminance signal difference value and the color difference signal difference value obtained from the horizontal interpolation data and the vertical interpolation data, respectively, with the parameters for the luminance signal and the parameters for the chrominance signal, and thus the luminance signal difference or the chrominance signal.
  • the interpolation direction can be determined in a direction where the difference is relatively small.
  • FIG. 2 is a flowchart illustrating a method of interpolating a color signal of an image according to an embodiment of the present invention.
  • the apparatus for interpolating the color signals of the image interpolates the color signals of the image for each channel to generate horizontal interpolation data and vertical interpolation data.
  • An apparatus for interpolating a color signal of an image may perform horizontal interpolation data including color signals of at least one channel interpolated in the horizontal direction based on a result of interpolating the color signal of the image for each channel.
  • Create The apparatus for interpolating the color signals of the image may generate vertical interpolation data including color signals of at least one channel interpolated in the vertical direction, based on a result of interpolating the color signals of the image for each channel.
  • this is only an embodiment of the present invention, and the apparatus for interpolating the color signal of the image may interpolate the color signal of the image based on a general interpolation method in addition to the horizontal or vertical interpolation method.
  • an apparatus for interpolating color signals of an image may generate horizontal interpolation data including a color signal of an interpolated R channel, a color signal of an interpolated B channel, and a color signal of a G channel interpolated in a horizontal direction.
  • the apparatus for interpolating the color signal of the image may generate vertical interpolation data including the color signal of the interpolated R channel, the color signal of the interpolated B channel, and the color signal of the G channel interpolated in the vertical direction.
  • the apparatus for interpolating the color signal of the image may obtain a difference value of the color signal between the target pixel and a pixel corresponding to the comparison pixel adjacent to the target pixel from the horizontal interpolation data and the vertical interpolation data, respectively.
  • the comparison pixel adjacent to the target pixel is a pixel existing within a predetermined range from the target pixel, and may be, for example, a pixel located at the top, bottom, left, and right sides of the target pixel. However, this is only an embodiment of the present invention, and a pixel positioned in a diagonal direction of the target pixel may be included in the comparison pixel according to the user's setting.
  • An apparatus for interpolating a color signal of an image may determine a pixel corresponding to a target pixel of an image for which the interpolation direction is to be determined, respectively, from horizontal interpolation data and vertical interpolation data.
  • the apparatus for interpolating the color signal of the image may determine a pixel corresponding to the comparison pixel adjacent to the target pixel in the horizontal interpolation data and the vertical interpolation data.
  • FIG. 5 to describe in detail a pixel corresponding to a target pixel and a comparison pixel adjacent to the target pixel, respectively.
  • pixels 512 and 514 corresponding to the target pixel 510 (hereinafter, the target pixel on the horizontal interpolation data) corresponding to the target pixel in the horizontal interpolation data and the comparison pixels adjacent to the target pixel. 516, 518, comparison pixels on horizontal interpolation data).
  • the target pixel 510 on the horizontal interpolation data may be a pixel 510 located at the same point as the position of the target pixel on the image among the plurality of pixels included in the horizontal interpolation data. .
  • comparison pixels 512, 514, 516, and 518 on the horizontal interpolation data may include pixels 512, which are located at the same point as the position where the comparison pixels are located on the image, among a plurality of pixels included in the horizontal interpolation data. 514, 516, 518).
  • pixels 522 and 524 corresponding to the target pixel 520 (hereinafter, the target pixel on the vertical interpolation data) corresponding to the target pixel in the vertical interpolation data and the comparison pixels adjacent to the target pixel. 526, 528, comparative pixels on vertical interpolation data).
  • the target pixel 520 on the vertical interpolation data may be a pixel 520 positioned at the same point as the target pixel on the image among the plurality of pixels included in the vertical interpolation data. .
  • comparison pixels 522, 524, 526, and 528 on the vertical interpolation data are located at the same point as the point where the comparison pixels are positioned on the image among the plurality of pixels included in the vertical interpolation data. 524, 526, 528).
  • step 230 the apparatus for interpolating the color signals of the image corresponds to the target pixel and the comparison pixel, based on the difference value of the color signal for each channel obtained from the horizontal interpolation data and the vertical interpolation data, respectively.
  • a luminance signal difference value and a color difference signal difference value between pixels can be obtained.
  • An apparatus for interpolating an image signal uses a difference value of a color signal obtained from horizontal interpolation data and vertical interpolation data, respectively, based on preset conversion condition information, and a difference between a luminance signal and a color difference signal. Can be converted to a value. That is, the apparatus for interpolating the image signal extracts a condition that matches the difference value of the color signal obtained from the preset conversion condition information, and then obtains a difference value conversion equation of the luminance signal corresponding to the extracted condition and a difference value conversion equation of the color difference signal. can do.
  • a method of setting the conversion condition information by the apparatus for interpolating the image signal will be described in detail later with reference to FIG. 4.
  • the apparatus for interpolating the image signal may calculate a luminance signal difference value and a color difference signal difference value corresponding to the difference value of the color signal based on preset conversion condition information. That is, the apparatus for interpolating the image signal provides information on the relationship between the difference value of each channel color signal and the luminance signal difference value and the relationship between the difference value of each channel color signal and the color difference signal difference value from preset conversion condition information. Can be obtained.
  • an apparatus for interpolating a color signal of an image is based on a difference value of a color signal between a target pixel 510 on horizontal interpolation data and comparison pixels 512, 514, 516, and 518 on horizontal interpolation data.
  • the luminance signal difference value (hereinafter referred to as the first luminance signal difference value) and the chrominance signal difference value (hereinafter referred to as “first”) between the target pixel 510 on the horizontal interpolation data and the comparison pixels 512, 514, 516, and 518 on the horizontal interpolation data.
  • first luminance signal difference value
  • first chrominance signal difference value
  • the apparatus for interpolating the color signal of the image is a target pixel 520 on the vertical interpolation data and the comparison pixels 522, 524, 526, 528 on the vertical interpolation data in the same manner as described above.
  • Luminance signal difference value hereinafter, second luminance signal difference value
  • a color difference signal difference value hereinafter, referred to as a second color difference signal difference value
  • An apparatus for interpolating a color signal of an image may use a luminance signal difference value and a color difference signal from a difference value of a color signal without undergoing a color space conversion process of an image color signal based on preset conversion condition information. It is possible to reduce the cost and time required to interpolate the image color signal in that the difference value can be obtained.
  • the apparatus for interpolating the color signals of the image may include the first luminance signal difference value and the first color difference signal difference value obtained from the horizontal interpolation data, and the second luminance signal difference value and the second color difference signal obtained from the vertical interpolation data.
  • the interpolation direction of the luminance signal of the target pixel and the interpolation direction of the color difference signal can be determined by comparing with the difference values, respectively.
  • an apparatus for interpolating a color signal of an image may include a first luminance signal difference between a target pixel 510 on horizontal interpolation data and comparison pixels 512, 514, 516, and 518 on horizontal interpolation data.
  • the second luminance signal difference value may be compared between the value and the target pixel 520 on the vertical interpolation data and the comparison pixels 522, 524, 526, and 528 on the vertical interpolation data.
  • An apparatus for interpolating a color signal of an image may select a luminance signal difference value having a higher luminance homogeneity with a target pixel of the image based on the comparison result. For example, an apparatus for interpolating a color signal of an image may determine that homogeneity is high when the luminance signal difference value is small. The apparatus for interpolating the color signal of the image may determine a direction corresponding to the selected luminance signal difference value as the interpolation direction of the luminance signal. For example, when the luminance homogeneity of the first luminance signal difference value is higher, the apparatus for interpolating the color signal of the image may determine the interpolation direction of the luminance signal in the horizontal direction corresponding to the first luminance signal difference value.
  • an apparatus for interpolating a color signal of an image includes a first color difference signal difference between a target pixel 510 on horizontal interpolation data and comparison pixels 512, 514, 516, and 518 on horizontal interpolation data.
  • a second color difference signal difference value may be compared between the value and the target pixel 520 on the vertical interpolation data and the comparison pixels 522, 524, 526, and 528 on the vertical interpolation data.
  • An apparatus for interpolating a color signal of an image may select a color difference signal difference value having a relatively higher color difference homogeneity with a target pixel of the image based on the comparison result. For example, an apparatus for interpolating a color signal of an image may determine that homogeneity is high when the color difference signal difference value is small. The device interpolating the color signal of the image may determine a direction corresponding to the selected color difference signal difference value as the interpolation direction of the color difference signal. For example, when the color difference homogeneity of the second body diagram signal difference value is higher, the apparatus for interpolating the color signal of the image may determine the interpolation direction of the color difference signal in a vertical direction corresponding to the second color difference signal difference value.
  • a device for interpolating a color signal of an image may determine a method of determining interpolation directions of luminance signals and interpolation directions of chrominance signals in a direction of higher homogeneity, respectively, with reference to FIG. 6. It will be described later.
  • FIG. 3 is a flowchart illustrating a method of obtaining a luminance signal difference value and a color difference signal difference value based on a channel signal difference value between a target pixel included in an image and a comparison pixel according to an exemplary embodiment of the present invention.
  • the apparatus for interpolating the color signals of the image may obtain a difference value of the color signal between the target pixel and a pixel corresponding to the comparison pixel adjacent to the target pixel from the horizontal interpolation data and the vertical interpolation data, respectively.
  • Step 310 may correspond to step 220 in FIG. 2.
  • the device interpolating the color signals of the image may compare the difference between the color signals obtained from the horizontal interpolation data and the vertical interpolation data with preset conversion condition information.
  • the conversion condition information may include information about a difference value of the luminance signal and a difference value of the color difference signal corresponding to the difference value of the color signal between the pixels.
  • An apparatus for interpolating color signals of an image may convert color signals of an RGB channel into luminance signals and color difference signals in a color space of YCoCg, unlike a general AHD algorithm.
  • the relationship between the color signal of the RGB channel and the luminance signal and the color difference signal in the color space of YCoCg is expressed by the following equation (1).
  • an apparatus for interpolating an image color signal may convert a color signal of an RGB channel into a luminance signal and a color difference signal of a YCgCo color space.
  • the process of converting the color signal of the RGB channel into the luminance signal and the color difference signal of the YCgCo color space is simpler than the process of converting the color signal of the existing RGB channel into the luminance signal and the color difference signal of the CIELab color space.
  • the amount of computation performed during the interpolation of color signals can be significantly reduced.
  • the apparatus for interpolating an image signal uses a Manhattan distance (MD) to display a difference value of a luminance signal and a difference value of a chrominance signal between a pixel corresponding to a target pixel and a comparison pixel adjacent to the target pixel.
  • MD Manhattan distance
  • Manhattan Distance is calculated by adding the distance between the vertical axis and the horizontal axis of two points, unlike Euclidean Distance, which calculates the length of the shortest straight distance between two points.
  • Manhattan Distance unlike Euclidean Distance, uses absolute values to measure distances, making system implementation easier and significantly improving computational performance.
  • An apparatus for interpolating a color signal of an image is based on a relationship between a color signal of an RGB channel, a luminance signal and a color difference signal in the YCgCo color space, and a color signal difference value of an image based on Manhattan distance.
  • the luminance signal difference value and the color difference signal difference value can be determined without a separate color space conversion.
  • the difference in the color signal for each RGB channel is as follows. Specifically, the difference (dR) of the color signal of the R channel may be determined as R1-R2, the difference (dG) of the color signal of the G channel, and the difference (dB) of the color signal of the G1-G2 and the B channel may be determined as B1-B2. .
  • Manhattan distance (d (Y)) of the luminance signals Y1 and Y2 may be represented by dR, dG, and dB as shown in Equation 2 below.
  • Manhattan Distance (d (c)) for the color difference signals C1 and C2 may also be expressed as dR, dG, and dB as follows.
  • the apparatus for interpolating the color signals of the image may include the second luminance signal difference value and the second color difference signal obtained by obtaining the first luminance signal difference value and the first color difference signal difference value obtained from the horizontal interpolation data from the vertical interpolation data.
  • the interpolation direction of the luminance signal of the target pixel and the interpolation direction of the color difference signal can be determined by comparing with the difference values, respectively.
  • Step 330 according to an embodiment of the present invention may correspond to step 240 of FIG. 2.
  • FIG. 4 is a flowchart illustrating a method of determining in detail a difference value of a luminance signal corresponding to a difference value of a color signal between pixels and a difference value of a color difference signal according to an embodiment of the present invention.
  • An apparatus for interpolating a color signal of an image is based on a difference value of color signals obtained from horizontal interpolation data and vertical interpolation data, and a difference value of a luminance signal and a difference value of a color difference signal without color space conversion. Can be obtained.
  • the apparatus for interpolating the color signal of the image may obtain the difference value of the luminance signal and the difference value of the chrominance signal from the difference value of the color signal without using the color space by using preset conversion condition information.
  • the device interpolating the color signals of the image may obtain a difference value of the color signals between the pixels.
  • the difference in the color signal for each RGB channel is as follows. Specifically, the difference (dR) of the color signal of the R channel may be determined as R1-R2, the difference (dG) of the color signal of the G channel, and the difference (dB) of the color signal of the G1-G2 and the B channel may be determined as B1-B2. .
  • the apparatus for interpolating the color signals of the image may display the difference value of the luminance signal based on the difference between the color signals of each channel of the two pixels. Based on the result of converting the color signal for each RGB channel of the image into the luminance signal and the chrominance signal of the YCgCo color space, the Manhattan distance of the luminance signal between pixels is obtained. Through d can be expressed as dR, dG, dB.
  • the Manhattan distance of the color difference signal between pixels is obtained.
  • dR, dG, and dB the final result of the difference value of the chrominance signal may vary.
  • Equation 3 (Hereinafter condition 1) and Based on the sign of the value obtained by calculating (hereinafter, condition 2), the final result of the difference value of the color difference signals may be different.
  • the apparatus for interpolating the color signals of the image may classify the difference values of the color difference signals based on the sign of the value obtained by calculating the condition 2.
  • the device interpolating the color signal of the image may classify the difference value of the color difference signal based on the sign of the value of Condition 1.
  • step 450 when both condition 1 and condition 2 are positive, the relationship between the difference values of the color signals for each channel may be summarized as in Equations 4 and 5 below.
  • step 460 when condition 1 is negative and condition 2 is positive, the relationship between the difference values of the color signals for each channel may be summarized by Equations 7 and 8 as follows.
  • the device interpolating the color signal of the image may classify the difference value of the color difference signal based on the sign of the value of Condition 1.
  • step 480 when condition 1 is positive and condition 2 is negative, the relationship between the difference values of the color signals for each channel may be summarized by Equations 10 and 11 as follows.
  • step 490 when condition 1 is negative and condition 2 is negative, the relationship between the difference values of the color signals for each channel may be summarized by Equations 13 and 14 as follows.
  • FIG. 6 is a flowchart illustrating a method of determining homogeneity parameters of luminance signals and homogeneity parameters of color difference signals, according to an embodiment of the present invention.
  • the apparatus for interpolating the color signals of the image may include the first luminance signal difference value and the magnitudes of the first luminance signal difference value and the second luminance signal difference value between the pixels corresponding to the target pixel and the comparison pixels positioned at the top and bottom of the target pixel, respectively.
  • the homogeneity parameter of the luminance signal and the homogeneity parameter of the chrominance signal based on the magnitudes of the first color difference signal difference value and the second color difference signal difference value between the pixels corresponding to the target pixel and the comparison pixels positioned on the left and right sides of the target pixel. Can be determined.
  • a detailed process of determining the homogeneity parameter of the luminance signal and the homogeneity parameter of the color difference signal according to an embodiment of the present invention is as follows.
  • the homogeneity parameter is based on the difference between pixels of the horizontal interpolation data and the vertical interpolation data. Is selected.
  • the apparatus for interpolating the color signals of the image may determine the homogeneity parameter and the homogeneity parameter of the color difference signal, and may determine the luminance signal difference value and the color difference signal difference value between the pixels except the compared pixels.
  • the homogeneity parameter and the homogeneity parameter of the chrominance signal can be compared.
  • Both horizontal and vertical distances compared to values can be reduced by taking advantage of the condition to determine the final selection without having to compare epsilon values.
  • the calculation process for the selection is shown below.
  • i) is a formula that develops the condition to be confirmed by arranging the equation when the selection of the homogeneity parameter becomes the horizontal direction, and ii) the equation when the homogeneity parameter of luminance is the horizontal direction and the homogeneity parameter of the color difference is the vertical direction. It is an expression that expands the conditions to be summarized and checked.
  • an apparatus for interpolating a color signal of an image may be further configured to determine whether a pixel having a luminance signal difference value smaller than the homogeneity parameter of the luminance signal is based on a result of comparing pixels and a result of comparing the remaining pixels. The number and number of pixels having a color difference signal difference smaller than the homogeneity parameter of the color difference signal may be determined.
  • the apparatus for interpolating the color signals of the image may determine the interpolation direction of the luminance signal of the target pixel and the interpolation direction of the chrominance signal based on the determined number of pixels in operation 630. For example, in an apparatus for interpolating a color signal of an image, among the pixels having the first luminance signal difference value, the number of pixels having the first luminance signal difference value smaller than the homogeneity parameter of the luminance signal is determined by the second luminance signal difference value. When the number of pixels having the second luminance signal difference value smaller than the homogeneity parameter of the luminance signal is large, the interpolation direction of the luminance signal may be determined as the horizontal direction. In the opposite case, the device interpolating the color signal of the image may determine the interpolation direction of the luminance signal as the vertical direction.
  • the apparatus for interpolating the color signal of the image has a second color difference signal difference value of the number of pixels having a first color difference signal difference value smaller than the homogeneity parameter of the color difference signal among the pixels having a first color difference signal difference value
  • the interpolation direction of the color difference signal may be determined as the horizontal direction. In the opposite case, the interpolation direction of the color difference signal may be determined as the vertical direction.
  • the apparatus 700 for interpolating a color signal of an image may include a color signal obtainer 710, a signal converter 720, and a determiner 730. ) May be included. However, not all illustrated components are essential components.
  • the device 700 for interpolating the color signal of the image may be implemented by more components than the illustrated component, and the device 700 for interpolating the color signal of the image may be implemented with fewer components.
  • the color signal acquirer 710 may generate horizontal interpolation data and vertical interpolation data based on a result of interpolating the color signals of the image for each channel. In addition, the color signal acquirer 710 may obtain a difference value of the color signal between the target pixel and a pixel corresponding to the comparison pixel adjacent to the target pixel from the horizontal interpolation data and the vertical interpolation data.
  • the signal converter 720 obtains the luminance signal difference value and the color difference signal difference value based on the difference value of the color signal between the target pixel and the pixel corresponding to the comparison pixel adjacent to the target pixel from the horizontal interpolation data and the vertical interpolation data, respectively. can do.
  • the signal converter 720 further includes a conversion condition comparator 722 for comparing a difference value of the color signal obtained from the horizontal interpolation data and the vertical interpolation data with preset conversion condition information. It may include.
  • the signal converter 720 may determine the difference between the first luminance signal and the first luminance signal corresponding to the difference value of the color signal obtained from the horizontal interpolation data based on the comparison result of the conversion condition comparison unit 722.
  • the apparatus may further include a difference value determiner 724 that determines a difference value of the second luminance signal and a difference value of the second color difference signal corresponding to the difference value of the color signal obtained from the difference value and the vertical interpolation data.
  • the determination unit 730 compares the first luminance signal difference value and the first color difference signal difference value obtained from the horizontal interpolation data with the second luminance signal difference value and the second color difference signal difference value obtained from the vertical interpolation data, respectively.
  • the interpolation direction of the luminance signal of the target pixel and the interpolation direction of the color difference signal may be determined.
  • the determination unit 730 may determine the difference between the first luminance signal difference value and the second luminance signal difference value between pixels corresponding to the target pixel and the comparison pixels positioned at the top and bottom of the target pixel, respectively.
  • the homogeneity parameter of the luminance signal and the chrominance signal of the luminance signal based on the magnitude and the magnitude of the first color difference signal difference value and the second color difference signal difference value between the pixels corresponding to the target pixel and the comparison pixels located on the left and right sides of the target pixel.
  • the apparatus may further include a parameter determiner 732 for determining homogeneity parameters.
  • the determining unit 730 determines the homogeneity parameter of the luminance signal and the homogeneity parameter of the color difference signal, and determines the luminance signal difference value and the color difference signal difference value among the remaining pixels except the compared pixels.
  • the apparatus may further include a homogeneity determiner 734 comparing the homogeneity parameter of the color difference signal. Homogeneity determination unit 734 is. The number of pixels having a luminance signal difference smaller than the homogeneity parameter of the luminance signal and the color difference signal difference smaller than the homogeneity parameter of the chrominance signal based on the result for the pixels compared in advance and the comparison result for the remaining pixels The number of can be determined.
  • the determination unit 730 may determine an interpolation direction of the luminance signal of the target pixel and the interpolation direction of the chrominance signal of the target pixel based on the number of pixels determined for the luminance signal and the chrominance signal of the target pixel, respectively. 736 may further include.
  • the device comprises a processor, a memory for storing and executing program data, a permanent storage such as a disk drive, a communication port for communicating with an external device, a user interface such as a touch panel, a key, a button and the like.
  • a user interface such as a touch panel, a key, a button and the like.
  • Methods implemented by software modules or algorithms may be stored on a computer readable recording medium as computer readable codes or program instructions executable on the processor.
  • the computer-readable recording medium may be a magnetic storage medium (eg, read-only memory (ROM), random-access memory (RAM), floppy disk, hard disk, etc.) and an optical reading medium (eg, CD-ROM). ) And DVD (Digital Versatile Disc).
  • the computer readable recording medium can be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion.
  • the medium is readable by the computer, stored in the memory, and can be executed by the processor.
  • the invention can be represented by functional block configurations and various processing steps. Such functional blocks may be implemented in various numbers of hardware or / and software configurations that perform particular functions.
  • the present invention relates to integrated circuit configurations such as memory, processing, logic, look-up table, etc., which may execute various functions by the control of one or more microprocessors or other control devices. It can be adopted.
  • the present invention includes various algorithms implemented in data structures, processes, routines or other combinations of programming constructs, including C, C ++ It may be implemented in a programming or scripting language such as Java, an assembler, or the like.
  • the functional aspects may be implemented with an algorithm running on one or more processors.
  • the present invention may employ the prior art for electronic environment setting, signal processing, and / or data processing.
  • Terms such as “mechanism”, “element”, “means” and “configuration” can be used widely and are not limited to mechanical and physical configurations. The term may include the meaning of a series of routines of software in conjunction with a processor or the like.
  • connection or connection members of the lines between the components shown in the drawings by way of example shows a functional connection and / or physical or circuit connections, in the actual device replaceable or additional various functional connections, physical It may be represented as a connection, or circuit connections.
  • such as "essential”, “important” may not be a necessary component for the application of the present invention.

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Color Image Communication Systems (AREA)
  • Color Television Image Signal Generators (AREA)

Abstract

L'invention concerne une technique d'interpolation du signal de couleur d'une image. La technique d'interpolation d'un signal de couleur d'une image peut réduire la quantité de calculs effectués au cours de l'interpolation du signal de couleur d'une image, en générant des données d'interpolation horizontale et des données d'interpolation verticale d'après le résultat d'interpolation du signal de couleur de l'image par canal, en obtenant une valeur de différence du signal de luminance et une valeur de différence du signal de différence de couleur entre des pixels correspondant respectivement à un pixel considéré et à un pixel comparé, d'après la valeur de différence du signal de couleur obtenue à partir des données d'interpolation horizontale et des données d'interpolation verticale, respectivement, et en déterminant la direction d'interpolation du signal de luminance et la direction d'interpolation du signal de différence de couleur du pixel considéré en comparant une première valeur de différence du signal de luminance et une première valeur de différence du signal de différence de couleur obtenue à partir des données d'interpolation horizontale à une deuxième valeur de différence du signal de luminance et à une deuxième valeur de différence du signal de différence de couleur obtenue à partir des données d'interpolation verticale.
PCT/KR2015/001061 2014-02-03 2015-02-02 Procédé et appareil d'interpolation du signal de couleur d'une image WO2015115866A1 (fr)

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