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WO1999064989A1 - Processeur d'images - Google Patents

Processeur d'images Download PDF

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Publication number
WO1999064989A1
WO1999064989A1 PCT/JP1999/003045 JP9903045W WO9964989A1 WO 1999064989 A1 WO1999064989 A1 WO 1999064989A1 JP 9903045 W JP9903045 W JP 9903045W WO 9964989 A1 WO9964989 A1 WO 9964989A1
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WO
WIPO (PCT)
Prior art keywords
pixel
image
image processing
sampling function
pixels
Prior art date
Application number
PCT/JP1999/003045
Other languages
English (en)
Japanese (ja)
Inventor
Kazuo Toraichi
Kouichi Wada
Original Assignee
Fluency Research & Development Co., Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Fluency Research & Development Co., Ltd. filed Critical Fluency Research & Development Co., Ltd.
Publication of WO1999064989A1 publication Critical patent/WO1999064989A1/fr

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Classifications

    • 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
    • G06T3/4007—Scaling of whole images or parts thereof, e.g. expanding or contracting based on interpolation, e.g. bilinear interpolation
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T5/00—Image enhancement or restoration
    • G06T5/80—Geometric correction

Definitions

  • the present invention relates to an image processing device that performs enlargement or reduction processing of an image composed of a plurality of pixels.
  • a case where the value of a function has a limited value other than 0 in a local region and becomes 0 in other regions is referred to as a “finite base” and described.
  • FIG. 10 is an explanatory diagram of a conventionally known sampling function called a sinc function.
  • the interpolation by the sinc function is performed by the function sin ⁇ 7T f (t-k T) ⁇ /; rf (t _ k T) It can be seen that this is realized by performing a so-called convolution operation, which shifts by kT in the time axis direction and multiplies the sample value.
  • the present invention has been made in view of the above points, and an object of the present invention is to provide an image processing apparatus capable of reducing image distortion due to an error and reducing the amount of calculation.
  • the image processing apparatus calculates the pixel positions of a plurality of pixels constituting the image after the image processing when a predetermined magnification for performing the enlargement processing or the reduction processing on the original image is specified. Later, interpolation processing for obtaining the pixel value of each of these pixels is performed by a convolution operation using a sampling function that is finitely differentiable and has a finite number of values. By using a sampling function having a finite number of values, only the pixel data corresponding to this finite number of sections is subject to interpolation calculation, so that the amount of calculation is small and no truncation error is generated. Interpolation accuracy can be obtained, and distortion of an image obtained by image processing can be reduced.
  • the pixel position calculation performed for each pixel of the image after the image processing be performed in a relative relationship to the pixel position of each pixel of the original image.
  • the relative positional relationship of each pixel becomes important. That is, the pixel position of each pixel of the image after image processing is calculated based on the relative relationship to the pixel position of each pixel of the original image, and the subsequent interpolation processing becomes possible by using the calculation result.
  • the sampling function H (t) to which the present invention is applied is represented by one F (t + 1/2) / 4 + F (, where F (t) is a third-order B-spline function. t)-F (t-1/2) / 4.
  • the third-order B-spline function F (t) described above is (4 t 2 + 1 2 t + 9) / 4 for one 3 / 2 ⁇ t ⁇ -1/2, and one l / 2 ⁇ t ⁇ l / 2 can be expressed as 1 2 t 2 + 3/2, and l / 2 ⁇ t ⁇ 3/2 as (4 t 2 _ 12 t + 9) / 4. Since the above-described sampling function operation can be performed by the piecewise polynomial according to, the operation content is relatively simple and the amount of operation can be reduced. Also, instead of using the B-spline function to represent the sampling function as described above, it can be represented by a quadratic piecewise polynomial.
  • the pixel value calculating means for performing the pixel value interpolation operation includes an interpolation target pixel extracting means, a sampling function operation means, and a convolution operation means for performing the above-described interpolation operation.
  • the interpolation target pixel extracting means extracts a plurality of pixels which are present in a predetermined range around the target pixel and which are to be subjected to the interpolation calculation.
  • the sampling function calculation means calculates the value of the sampling function H (t) for each of the plurality of pixels extracted in this way, where t is the distance between the pixel of interest and the convolution calculation means.
  • FIG. 1 is a diagram illustrating a configuration of an image processing apparatus according to an embodiment
  • FIG. 2 is a diagram showing an outline of an image enlargement process performed by the image processing apparatus shown in FIG. 1,
  • FIG. 3 is a diagram showing a detailed configuration of the pixel value calculation unit
  • FIG. 4 is a diagram showing a range of constituent pixels of an original image extracted around a pixel of interest.
  • FIG. 5 is an explanatory diagram of a sampling function used in the operation in the sampling function operation unit.
  • FIG. 6 is an explanatory diagram of a distance calculation between the target pixel p and each interpolation target pixel performed by the sampling function operation unit.
  • FIG. 7 is a diagram showing a specific example of calculating the value of the sampling function at the pixel of interest corresponding to each interpolation target pixel
  • FIG. 8 is a diagram showing an outline of a modification of the image enlarging process performed by the image processing device shown in FIG. 1,
  • FIG. 9 is an explanatory diagram when the interval at which the value of the sampling function becomes 0 is changed according to the relative direction between each interpolation target pixel and the pixel of interest.
  • FIG. 10 is an explanatory diagram of the sinc function.
  • Enlarging or reducing an image composed of a plurality of pixels means increasing or decreasing the number of constituent pixels according to a predetermined magnification while maintaining the contour shape of the original image.
  • the feature of the present embodiment lies in that the process of increasing or decreasing is performed by an interpolation operation using a predetermined sampling function.
  • FIG. 1 is a diagram showing a configuration of an image processing apparatus according to an embodiment to which the present invention is applied.
  • the image processing apparatus 1 shown in FIG. 1 includes a pixel data storage unit 10, a pixel position calculation unit 20, a pixel value calculation unit 30, and a pixel data storage unit 40.
  • the pixel data storage unit 10 stores the pixel data of each pixel constituting the original image.
  • C The pixel data includes the pixel position and the pixel value of each pixel.
  • the pixel position is address information of each pixel constituting the original image, and includes an X address along the horizontal direction and a Y address along the vertical direction.
  • the X address and the Y address may be implicitly indicated by an array of pixel values or the like in addition to the case where the X address and the Y address are explicitly specified as part of the pixel data.
  • the pixel value is a data that indicates the characteristics of each pixel, and for example, grayscale data, color data, luminance data, and the like of each pixel correspond thereto.
  • the pixel position calculation unit 20 calculates the scaling factor a when the image scaling factor a is specified. Then, the pixel positions of the pixels constituting the image obtained by the image processing are calculated based on the relative relationship with respect to the pixel positions of the pixels constituting the original image before the image processing. For example, (1) After virtually shifting the pixel position of each pixel constituting the original image so that the pixel interval becomes a times as large as the pixel interval, the image is adjusted so that the pixel interval becomes the same as the original pixel interval of the original image.
  • the pixel position of each pixel that constitutes the image after processing It is possible to calculate each pixel position by changing the interval to 1 / a times.
  • the pixel value calculation unit 30 calculates a pixel value of each pixel forming the image after the image processing by performing a predetermined interpolation process based on the pixel value of each pixel forming the original image.
  • the pixel data storage unit 40 stores the pixel value of each pixel calculated by the interpolation process and the pixel value of each pixel as pixel data after image processing.
  • the image processing device 1 of the present embodiment has such a configuration, and the operation will be described next. As described above, since a specific procedure of calculating the pixel position performed prior to the interpolation processing can be implemented in a number of modifications, each case will be described separately.
  • FIG. 2 is a diagram illustrating an outline of an image enlargement process performed by the image processing apparatus 1 illustrated in FIG. FIG. 2 (a) partially shows constituent pixels of an original image in which pixel data is stored in the pixel data storage unit 10, and asterisks indicate each pixel.
  • L be the pixel interval along each of the X and Y directions.
  • the pixel position calculation unit 20 performs a process of changing the pixel position of each pixel constituting the original image according to the specified scaling factor a. For example, when the magnification ratio a is greater than 1 (in the case of the enlargement process), as shown in FIG. 2 (b), the pixel position of each pixel constituting the original image is set to a predetermined enlargement center position (see FIG. 2 In (b), the pixel located at the upper left is set as the enlargement center position), and the distance from each pixel position is changed to a times.
  • each of the constituents of the original image is After changing the pixel position of the pixel, the pixel position calculation unit 20 determines each pixel position having the same pixel interval L as the original pixel interval L as indicated by a mark in FIG. It is set as each pixel position constituting the image.
  • the pixel positions that make up the image after image processing are set with reference to the upper left pixel as in the original image, but this reference position can be set arbitrarily and is not necessarily There is no need to match any pixel location in the image.
  • the pixel value calculation unit 30 calculates the pixel value of each pixel constituting the image after the image processing by a predetermined interpolation process.
  • the pixel values of the pixels arranged at the pixel interval L are calculated by interpolation based on the pixel values of the pixels arranged at the pixel interval aL.
  • the pixel position and pixel value of each pixel calculated by the interpolation processing in this manner are stored in the pixel data storage unit 40 as pixel data of each pixel constituting the image after the image processing.
  • FIG. 3 is a diagram showing a detailed configuration of the pixel value calculation unit 30.
  • the pixel value calculation unit 30 is configured to include an interpolation target pixel extraction unit 32, a sampling function calculation unit 34, and a convolution calculation unit 36.
  • the interpolation target pixel extraction unit 32 includes, from among a plurality of pixels constituting the original image, a pixel included in a predetermined range around a pixel whose pixel value is to be calculated by the interpolation processing (hereinafter, referred to as a “pixel of interest”). Is extracted and held.
  • a pixel of interest a pixel included in a predetermined range around a pixel whose pixel value is to be calculated by the interpolation processing
  • pixel of interest one of the pixels (marked with ⁇ ) constituting the image after image processing shown in FIG. 2 (c) is set as a target pixel, and a plurality of pixels (( Those included in a predetermined range centered on the pixel of interest are selected from ( ⁇ ).
  • Figure 4 shows the range of constituent pixels of the original image extracted around the pixel of interest c .
  • the interpolation target pixel extraction unit 32 extracts pixels included in a range of two pixels before and after each pixel in the X direction and the Y direction around the pixel of interest p. Since the pixel interval of each pixel constituting the original image is set to a L by the pixel position calculating unit 20, the address in the X direction and the Y back from the pixel of interest p is from ⁇ 2 a L. The constituent pixels of the original image included in the range of 2 a L are extracted.
  • the sampling function calculation unit 34 calculates the distance between each interpolation target pixel extracted by the interpolation target pixel extraction unit 32 and the pixel of interest p, and calculates the value of the sampling function based on the calculated distance. I do.
  • the value of the sampling function is calculated for each of the 16 interpolation target pixels extracted by the interpolation target pixel extraction unit 32.
  • the convolution operation unit 36 multiplies the values of the 16 standardization functions calculated by the sampling function operation unit 34 by the pixel values of the corresponding pixels to be interpolated, and adds the results. Performs a convolution operation.
  • the interpolation value obtained by this convolution operation is the pixel value of the pixel of interest p.
  • the above-described pixel data storage unit 10 is a first data storage unit
  • a pixel position calculation unit 20 is a pixel position calculation unit
  • a pixel value calculation unit 30 is a pixel value calculation unit
  • a pixel data storage unit. 40 corresponds to the second pixel data storage means.
  • the interpolation target pixel extraction unit 32 corresponds to the interpolation target pixel extraction unit
  • the sampling function operation unit 34 corresponds to the sampling function operation unit
  • the convolution operation unit 36 corresponds to the convolution operation unit.
  • FIG. 5 is an explanatory diagram of a sampling function used in the calculation in the sampling function calculation unit 34.
  • FIG. 6 is an explanatory diagram of the distance calculation between the pixel of interest p and each pixel to be interpolated performed by the sampling function calculation unit 34.
  • the pixel of interest p and some of the pixels to be interpolated are shown.
  • Pi indicates the pixel value of the pixel to be interpolated arranged at coordinates, Yj).
  • the sampling function calculator 34 calculates the value at the position of the pixel of interest p for the sampling function H (t) corresponding to each pixel to be interpolated. Is calculated.
  • the convolution operation unit 30 calculates the value of each of the obtained sampling functions as the pixel of each interpolation target pixel.
  • the values ⁇ and ⁇ are multiplied, and a convolution operation is performed by adding the result of the multiplication for all of the 16 interpolation target pixels to output a pixel value ⁇ ⁇ which is an interpolation value corresponding to the target pixel ⁇ .
  • the pixel values of all the pixels constituting the image after the image processing are calculated by the interpolation calculation.
  • the image processing apparatus 1 of the present embodiment uses a finite number of functions that can be differentiated only once over the entire area as the sampling function, the pixel of each pixel constituting the image obtained by the image processing is used. The amount of calculation required to calculate the value by interpolation can be greatly reduced.
  • the sampling function used in the present embodiment is of a finite scale, there is no truncation error that occurs when the number of pixels to be subjected to the interpolation operation is reduced to a finite number in the related art.
  • an interpolation result with a small error can be obtained. For this reason, it is possible to reduce distortion generated in the shape, color, and the like of an image obtained by image processing.
  • the interval between the pixels constituting the original image is virtually widened according to the magnification of the image processing, and the image after the image processing is processed based on the pixel value of each pixel having the widened interval.
  • the pixel values of the constituent pixels were obtained by interpolation processing, the pixel values of the constituent pixels of the image after image processing may be obtained without virtually widening the intervals between the constituent pixels of the original image. Good.
  • the number of pixels in the X direction and the Y direction of the enlarged image becomes a times.
  • the interval L between pixels constituting the original image is 1 / a
  • the multiplied pixel positions may be obtained by calculation, and then the pixel values corresponding to these pixel positions may be obtained by interpolation processing.
  • FIG. 8 is a diagram showing an outline of a modification of the image enlarging process performed by the image processing apparatus 1 shown in FIG. FIG. 8 (a) partially shows constituent pixels of an original image in which pixel data is stored in the pixel data storage unit 10, and a symbol indicates each pixel. Let the pixel spacing be along each of the X and Y directions.
  • the interpolation position calculation unit 20 calculates the pixel position of each pixel constituting the image obtained by the image processing based on the pixel data of each pixel stored in the pixel data storage unit 10 .
  • the position where the dotted line in FIG. 8B intersects is the pixel position to be calculated, and the pixel position is calculated such that the adjacent intervals in the X and Y directions are L / a.
  • the pixel value calculation unit 30 calculates the pixel value of each pixel corresponding to the pixel position calculated by the interpolation position calculation unit 20 (indicated by ⁇ in FIG. 8 (c)) into each pixel constituting the original image. 'Calculate by interpolation processing using the pixel value of ((in Fig. 8 (c)).
  • the pixel The interpolation processing itself performed by the value calculation unit 30 is basically the same as the interpolation processing outlined in FIG. 2, and is realized by the configuration shown in FIG.
  • any pixel for which a pixel value is to be obtained by an interpolation operation is defined as a pixel of interest p, and a plurality of pixels included in the original image in each of the X direction and the Y direction centering on the pixel of interest P , 16 pixels included in the range of two pixels before and after are extracted as interpolation target pixels.
  • the relationship shown in Fig. 4 is applied as it is to the relationship between the pixel of interest p and the 16 interpolation target pixels, and the pixel value of the pixel of interest p is calculated by a convolution operation using the sampling function shown in Fig. 5. Is done.
  • the pixel position of each pixel constituting the image obtained by the image processing is directly calculated, and the pixel value corresponding to this pixel position is calculated by the interpolation process. Accordingly, image processing at a predetermined magnification can be performed. Since this interpolation process is performed using a finite number of functions that can be differentiated only once in the entire area as a sampling function, the amount of computation required to calculate the pixel value of each pixel can be significantly reduced. In addition, since no truncation error occurs, it is possible to prevent an image obtained by the image processing from being distorted or changed in color.
  • the present invention is not limited to the above embodiment, and various modifications can be made within the scope of the present invention.
  • a case where the original image is enlarged at a predetermined magnification is described as a specific example of the image processing.
  • a case where the original image is reduced at a predetermined magnification can be similarly considered.
  • the sampling function is a finite-level function that can be differentiated only once in the entire region.
  • the number of differentiable times may be set to two or more.
  • the interval t O at which the value of the sampling function H (t) becomes 0 is set to the same value 1 (normalized as the interval in the X and Y directions of each pixel constituting the original image). ), But may be set to the interval 2 between each of the pixels adjacent in a diagonal direction of 45 °.
  • the above sampling function can be used as it is by calculating H (t / 2).
  • the above-described interval to ′ may be set to a value b that satisfies 1 ⁇ b ⁇ 2.
  • H (t By calculating / b) the above-mentioned sampling function can be used as it is.
  • the interval t 0 at which the value of the sampling function H (t) becomes 0 may be changed according to the relative direction between each pixel constituting the original image and the interpolation target image.
  • the interval t0 is set according to the direction connecting the pixel of interest p ( ⁇ ) and each pixel to be interpolated (image). Specifically, when the angle between the direction connecting the pixel of interest p and each pixel to be interpolated and the horizontal or vertical direction is 0 ( ⁇ 45 °), the above-described interval t 0 is 1 / cos ⁇ Set to.
  • c can be used as a sampling function described above also, in the above embodiment, a sampling function with a B-spline function F (t) H (t) is defined, and the sampling function H (t) is calculated using a quadratic piecewise polynomial.
  • the pixel value of each of these pixels is obtained.
  • the interpolation process is performed by convolution using a sampling function that is finitely differentiable and has finite values.
  • a sampling function having a finite number of values only the pixel data corresponding to this finite number of sections is subjected to the interpolation calculation, so that the amount of calculation is small and no truncation error is generated. It is possible to obtain high interpolation accuracy and reduce distortion of an image obtained by image processing.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Theoretical Computer Science (AREA)
  • Image Processing (AREA)
  • Editing Of Facsimile Originals (AREA)

Abstract

L'invention porte sur un processeur d'images capable de réduire les distorsions d'image dues à une erreur, et de traiter une image avec peu de calculs. Une fois le rapport d'agrandissement/réduction précisé, une unité de calcul de la position des pixels (20) calcule en fonction dudit rapport la position relative de chacun des pixels constitutifs de l'image formée par le traitement d'image. Une unité de calcul de la valeur des pixels (30) calcule les valeurs de pixels des pixels correspondant aux positions respectives des pixels calculés en effectuant des interpolations prédéterminées en utilisant les valeurs de pixels des pixels de l'image originale comprises dans une zone prédéterminée l'entourant. L'unité de calcul de la valeur des pixels (30) utilise une fonction d'échantillonnage différentiable un nombre fini de fois et présentant des valeurs finies pour l'interpolation.
PCT/JP1999/003045 1998-06-10 1999-06-08 Processeur d'images WO1999064989A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP10178122A JPH11353472A (ja) 1998-06-10 1998-06-10 画像処理装置
JP10/178122 1998-06-10

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WO1999064989A1 true WO1999064989A1 (fr) 1999-12-16

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PCT/JP1999/003045 WO1999064989A1 (fr) 1998-06-10 1999-06-08 Processeur d'images

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TW (1) TW440802B (fr)
WO (1) WO1999064989A1 (fr)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20110188583A1 (en) 2008-09-04 2011-08-04 Japan Science And Technology Agency Picture signal conversion system
WO2010058735A1 (fr) * 2008-11-21 2010-05-27 独立行政法人科学技術振興機構 Dispositif et procédé de traitement d'images
JP4693895B2 (ja) * 2008-12-05 2011-06-01 独立行政法人科学技術振興機構 画像処理装置および方法
JP4650958B2 (ja) * 2008-11-21 2011-03-16 独立行政法人科学技術振興機構 画像処理装置、方法およびプログラム

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH04330858A (ja) * 1991-05-02 1992-11-18 Toppan Printing Co Ltd ディジタル画像の拡大・縮小の方法およびその装置
JPH04354068A (ja) * 1991-05-31 1992-12-08 Konica Corp 画像データ補間方法及び装置

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH04330858A (ja) * 1991-05-02 1992-11-18 Toppan Printing Co Ltd ディジタル画像の拡大・縮小の方法およびその装置
JPH04354068A (ja) * 1991-05-31 1992-12-08 Konica Corp 画像データ補間方法及び装置

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TW440802B (en) 2001-06-16

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