Classifications

• • G—PHYSICS
  • G06—COMPUTING; CALCULATING OR COUNTING
  • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
  • G06T5/00—Image enhancement or restoration
  • G06T5/40—Image enhancement or restoration using histogram techniques
• • 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
  • H04N1/64—Systems for the transmission or the storage of the colour picture signal; Details therefor, e.g. coding or decoding means therefor
  • H04N1/644—Systems for the transmission or the storage of the colour picture signal; Details therefor, e.g. coding or decoding means therefor using a reduced set of representative colours, e.g. each representing a particular range in a colour space
• • G—PHYSICS
  • G06—COMPUTING; CALCULATING OR COUNTING
  • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
  • G06T7/00—Image analysis
  • G06T7/90—Determination of colour characteristics

Definitions

• the present invention relates to a method for abstracting a histogram of HSV colors, and more particularly, to a method for fast abstraction of a histogram of HSV colors from a still or motion picture stored in a YCbCr format.
• RGB Red, Green, and Blue
• CMY Cyan, Magenta, and Yellow
• YCbCr Gamma transformed luminance/color difference separation color model
• HSV typical color model used in a Computer Graphic field
• the YCbCr color model very efficient in compressing a picture data, is used in most of picture compressing international standards, such as JPEG (Joint Photographic Coding Experts Group), MPEG (Moving Picture Experts Group), and the like.
• the YCbCr color model indicates ratios of three components of luminance information 'Y', color difference information 'Cb', and 'Cr' included in a horizontal line of a TV screen and the like, wherein the luminance of a pixel is represented with 8bits, and the color of the pixel is represented with the color difference information by using two 8bits.
• FIG. 1 illustrates a block diagram of a related art HSN color histogram abstractor.
• the related art HSV color histogram abstractor for abstracting a HSV color histogram from the YCbCr color model, is provided with a YCbCr/ ⁇ SV converter 101 for converting a pixel value from the YCbCr color model to the HSV color model, a quantizer 102 for quantizing the HSV color model converted at the YCbCr/HSV converter 101 to provide a histogram index, and a histogram generator 103 for increasing a histogram BIN value of the histogram index from the quantizer 102 by one, to generate a histogram.
• the YCbCr/HSV converter 101 converts a pixel value from the YCbCr color model to the HSV color model with the following equations.
• H _ tan -1 S— - 180, 0D HD 360 (1)
• V Y, 0 ⁇ V ⁇ 255 (3)
• the quantizer 102 quantizes the pixel value of the HSV model, to obtain a histogram index.
• a case of quantization as shown in FIG. 3 will be described.
• the HSV model is represent with a three dimensional
• HSV HSV cylindrical coordinate system
• an axis of the cylinder represents 'V
• a concentric circular direction starting from a center (0) represents 'S'
• an angle represents 'H'.
• a method for quantizing the three dimensional HSV space represented thus is illustrated in sections of an HS plane and an SV plane.
• a pixel, having an 'S' equal to or smaller than 5, is regarded as a gray scale, and quantized only with respect to 'V in four stages each with 64 levels regardless of an H value.
• a color, having the 'S' greater than 5 and equal to or smaller than 30, is quantized with respect to 'H' in six stages each with 60 degrees, and 'V in two stage each with 128 levels.
• a color, having the 'S' greater than 30, is quantized only with respect to 'H' in six stages each with 60 degrees while disregarding 'V.
• a part having the S greater than 30 is quantized coarser than a part having the S smaller than 30 for reflecting a probability that occurrence of great S is relatively small in natural pictures.
• a histogram having 22 BINs (four stages with respect to 'V for a pixel having S smaller than 5, six stages with respect to 'H' and two stage with respect to 'V (2x6) for a color having an S greater than 5 and smaller than 30, and six stages with respect to 'H' for a color having an S greater than 30) is drawn up.
• the quantizer 102 determines a given pixel value of being a point belonging to which of 22 sections divided by circular, and radial boundaries in the three dimensional HSV space, and provides an index value between 0 to 21 representing the section.
• the histogram generating part 103 increases a BIN value of the histogram for the index by one, to draw up the histogram.
• the related art method for abstracting an HSV color histogram from a picture in the YCbCr color model has the following problems.
• An object of the present invention designed to solve the foregoing problem lies on providing a method for abstracting an HSV color histogram from a YCbCr format picture, not by using a related art method in which a picture stored in a YCbCr color model is converted into an HSV model, and the converted HSV color model is quantized in an HSV space, but by receiving the YCbCr color model in advance, making a Lookup table (LUT) which can provide a histogram index, and abstracting the HSV histogram with reference to the lookup table, for dispensing with the complicate operations.
• LUT Lookup table
• the object of the present invention can be achieved by providing a method for abstracting a histogram of HSV colors, including the steps of drawing up lookup tables each divided into a plurality of sections each having a quantizing index value stored therein, for receiving a YCbCr and providing an HSV histogram index, selecting one section of the lookup table according to a Y signal and a CbCr signal of a YCbCr model, and abstracting the histogram with reference to the index of the selected section.
• the step of drawing up lookup tables includes the steps of drawing up N lookup tables corresponding to Cb and Cr, dividing each of the N lookup tables with M concentric circles corresponding to S quantizing boundaries from a center, dividing each of the N lookup tables with L radial lines to form sections, and storing a quantizing index in each of sections of the N lookup tables.
• a number of the lookup tables is four, each divided by concentric circles with 5, and 30 radii from the center respectively, and by six radial lines again for sections with a radius greater than 5, for storing quantizing indices therein respectively.
• a method for abstracting a histogram of HSV colors in a case H, S, and V are respectively quantized in L, M, and N levels comprising the steps drawing up N lookup tables corresponding to Cb and Cr, dividing each of the N lookup tables with M concentric circles corresponding to S quantizing boundaries from a center, dividing each of the N lookup tables with L radial lines to form sections, storing a quantizing index in each of sections of the N lookup tables, shifting a luminance signal Y of received YCbCr to right by (8- log2N) bits when N is a power of 2, and dividing Y with N when N is not a power of 2, and selecting one of the N lookup tables, and picking up
• FIG. 1 illustrates a block diagram of abstracting an HSV color histogram from a YCbCr format picture in the related art
• FIG. 2 illustrates a block diagram of abstracting an HSV color histogram from a YCbCr format picture in accordance with a preferred embodiment of the present invention
• FIGS. 3 A ⁇ 3C illustrate an example of a quantizing method in an HSV space in accordance with the present invention.
• FIG. 4 illustrates an exemplary diagram for describing a method for making and referring to an LUT of the present invention. Best Mode for Carrying Out the Invention
• lookup tables LUTl ⁇ LUT4 each with 256x256 height and width size in correspondence to Cb and Cr are drawn up in advance.
• Each of the lookup tables LUTl ⁇ LUT4 is divided by concentric circles with radii 5 and 30 from a center (0, 0), and six radial lines at 60° intervals starting from 138° for a section thereof outside of radius 5.
• the section is divided by six radial lines at 60° intervals starting from 138° because an 108° on a Cb, or Cr plane corresponds to 0° on an H plane, i.e., for dividing the lookup table into six sections at 60° intervals centered on 0° of an H plane, it is required to draw six radial lines at 60° intervals centered on 108°, resulting to obtain a section from 138° to 78°, which is 108° ⁇ 30°, and divide the lookup table with radial lines at 60° intervals starting from 138°.
• a quantizing index value is stored in each section of the lookup table. That is, referring to FIG. 3C, since the section with a radius below 5 on the SV plane is divided in four stages each with 64 levels, four lookup tables are drawn up, and different quantizing index values are respectively stored in the sections of the lookup tables with radii below 5 accordingly (a quantizing value of "0" is stored in LUTl, a quantizing value of "1” is stored in LUT2, a quantizing value of "2” is stored in LUT3, and a quantizing value of "3” is stored in LUT4).
• a section having a radius greater than 5 but smaller than 30 on the SV plane is divided into two sections, though identical quantizing values are stored in sections of the first and second lookup tables LUTl and LUT2 each with a radius greater than 5 but below 30, and identical quantizing values are stored in sections of the third and fourth lookup tables LUT3 and LUT4 each with a radius greater than 5 but below 30, different quantizing values are stored in sections of the first and second lookup tables LUTl and LUT2, and the third and fourth lookup tables LUT3 and LUT4, each with a radius greater than 5 but below 30.
• a method for abstracting a histogram of HSV colors from the YCbCr color model of the present invention by using the lookup tables drawn up thus will be described.
• a pixel value of the YCbCr color model is provided, by shifting a luminance signal 'Y' to right, one of the four lookup tables is selected with reference to a value corresponding to the most significant two bits, where a value corresponding to Cb and Cr can be obtained, which is the quantizing index at the time converted into the HSV model and quantized.
• the lookup tables drawn up thus can be summarized as follows.
• H, S, and V are respectively quantized in L, M, and N levels, after preparing a system in which 'N' lookup tables each with a 256x256 size corresponding to Cb and Cr are drawn up, so that one of N lookup tables is selected by shifting Y to right by (8-log2N) bits when N is a power of 2, and subjecting Y to an integer dividing operation with N when N is not a power of 2, and a value corresponding to Cb and Cr is picked up from the lookup table, and after dividing each of the lookup table with M concentric circles for a range starting from a 128 radius from a center of the lookup table to an 'S' radius quantizing boundaries, and with L radial lines at regular intervals, a quantizing index is stored in each section.
• the method for abstracting a histogram of HSV colors from a YCbCr format of the present invention has the following advantages.
• the abstracting method of the present invention is useful not only in a case when an HSV color histogram is abstracted from a still picture stored in a format, such as JPEG, but also in a case a fast processing of a large amount of data, such as analyzing a large amount of digital video, such as an HDTV broadcasting stream.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Theoretical Computer Science (AREA)
• Computer Vision & Pattern Recognition (AREA)
• Multimedia (AREA)
• Signal Processing (AREA)
• Color Image Communication Systems (AREA)
• Facsimile Image Signal Circuits (AREA)
• Processing Of Color Television Signals (AREA)

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• 2001
  • 2001-03-20 KR KR10-2001-0014407A patent/KR100413341B1/ko active IP Right Grant
• 2002
  • 2002-05-20 WO PCT/KR2002/000950 patent/WO2003098550A1/en not_active Application Discontinuation
  • 2002-05-20 US US10/514,528 patent/US7447352B2/en not_active Expired - Fee Related
  • 2002-05-20 EP EP02736218A patent/EP1514237B1/en not_active Expired - Lifetime
  • 2002-05-20 DE DE60233000T patent/DE60233000D1/de not_active Expired - Fee Related
  • 2002-05-20 AU AU2002309288A patent/AU2002309288A1/en not_active Abandoned

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