JP4116517B2 - Image encoding device, image encoding method, image encoding program, image decoding device, image decoding method, and image decoding program - Google Patents

Description

  The present invention relates to an image encoding device, an image encoding method, an image encoding program, an image decoding device, an image decoding method, and an image decoding program.

In a conventional image encoding apparatus, generally, an encoding target image to be encoded is decomposed into DCT coefficients by DCT (Discrete Cosine Transform), and the DCT coefficients are encoded by an encoding method such as entropy encoding. For example, although the present invention relates to an image encoding device for encoding a moving image, a difference image between a prediction image generated by performing motion compensation prediction on an encoding target frame and the encoding target frame is calculated. As an encoding target image, there is an image encoding apparatus that decomposes this difference image into DCT coefficients by DCT and encodes the DCT coefficients (for example, Patent Document 1).
Japanese Patent Laid-Open No. 7-264592

  In orthogonal transform processing such as the two-dimensional DCT used in the above-described image encoding apparatus and the two-dimensional DWT (Discette Wavelet Transform) that is becoming popular as an image decomposition method, a specific pattern such as an edge included in an image is efficiently generated. It cannot be disassembled. In particular, in order to decompose a pattern such as an edge extending in a one-dimensional direction by a two-dimensional DWT, many coefficients are required. Therefore, the conventional image coding apparatus has a problem that efficient image coding cannot be realized.

  SUMMARY An advantage of some aspects of the invention is that it provides an image encoding device, an image encoding method, and an image encoding program capable of realizing efficient encoding. Further, the present invention provides an image decoding apparatus capable of faithfully reproducing a decoded image of an encoding target image based on compressed data generated by an image encoding apparatus of the present invention or a computer operating by an image encoding program, It is an object to provide an image decoding method and an image decoding program.

In order to solve the above problems, an image encoding apparatus according to the present invention includes (a) edge extraction means for extracting edge components in the horizontal and vertical directions of an image to be encoded, and (b) the edge components in the horizontal direction. Projected horizontal edge projection data, projection means for generating vertical edge projection data obtained by projecting the edge component in the vertical direction, and (c) a first orthogonal transform to each of the horizontal edge projection data and the vertical edge projection data. First transform means for generating a first set of coefficients obtained by performing processing; and (d) a first inverse transform that is an inverse transform process of the first orthogonal transform process on the first coefficient set. subjected to a treatment and recovery horizontal edge projection data and first inverse conversion means for generating a restoration vertical edge projection data, (e) and the encoding target image, the restoration horizontal edge projection data and the restored vertical edge projection A converted image generating means for generating a converted image formed by performing a subtraction between the restoration edge component based on back projection of over data, first formed by subjecting the second orthogonal transform processing in (f) the conversion target image code for generating a second conversion means for generating a set of second coefficients, the compressed data including the compressed code comprising applying encoding processing to the set of the set and a second coefficient of (g) the first coefficient Means.

In the image encoding method of the present invention, (a) an edge extracting unit extracts an edge component in the horizontal and vertical directions of an encoding target image; and (b) a projecting unit includes the edge component. A horizontal edge projection data obtained by projecting the edge component in the horizontal direction, and a projection step for generating vertical edge projection data obtained by projecting the edge component in the vertical direction; and (c) a first conversion means comprising the horizontal edge projection data and the vertical projection data. A first transform step for generating a first set of coefficients obtained by subjecting each of the edge projection data to a first orthogonal transform process; and (d) a first inverse transform means for the first set of coefficients. A first inverse transform step for generating a restored horizontal edge projection data and a restored vertical edge projection data by performing a first inverse transform process, which is an inverse transform process of the first orthogonal transform process, on (e) an object to be transformed Picture Generating means generates converted image generated with the encoding target image, the converted image formed by performing a difference operation between the restoration horizontal edge projection data and the restored vertical edge recovery edge component based on back projection of the projection data (F) a second transformation step in which a second transformation means generates a second set of coefficients obtained by subjecting the transformation target image to a second orthogonal transformation process; and (g) an encoding means. but including an encoding step of generating compressed data including compressed code comprising applying encoding processing to the set of the set and a second coefficient of the first coefficient.

The image encoding program according to the present invention includes a computer that (a) extracts edge components in the horizontal and vertical directions of an image to be encoded, and (b) projects the edge components in the horizontal direction. Projection means for generating horizontal edge projection data and vertical edge projection data obtained by projecting the edge component in the vertical direction; and (c) a first orthogonal transformation process for each of the horizontal edge projection data and the vertical edge projection data. First transform means for generating a first set of coefficients, and (d) a first inverse transform process that is an inverse transform process of the first orthogonal transform process on the first coefficient set. first inverse transform unit, (e) and the encoding target image, the restoration horizontal edge projection data and the restoration vertical edges subjected to generate a restored horizontal edge projection data recovery vertical edge projection data A converted image generating means for generating a converted image formed by performing a subtraction between the restoration edge component based on back projection of the shadow data, first formed by subjecting the second orthogonal transform processing in (f) the conversion target image code for generating a second conversion means for generating a set of second coefficients, the compressed data including the compressed code comprising applying encoding processing to the set of the set and a second coefficient of (g) the first coefficient To function as a means for making a change.

According to these inventions, the horizontal projection edge data obtained by projecting the horizontal edge component of the encoding target image in the horizontal direction and the vertical edge projection data obtained by projecting the vertical edge component in the vertical direction are one-dimensional. Signal. Therefore, the horizontal projection edge data and the vertical edge projection data can be decomposed into a small number of coefficients by the first orthogonal transformation process. Further, the difference obtained by removing the restored edge component from the encoding target image is obtained by removing one-dimensional edges extending in the horizontal direction and the vertical direction. Therefore, the transform target image obtained by performing the difference calculation between the encoding target image and the restored edge component can be decomposed into a small number of coefficients by the second orthogonal transform process. Since the encoding target image can be decomposed into a small number of coefficients in this way, efficient encoding is realized.

  Further, in the image encoding device of the present invention, the edge extraction means performs one-level wavelet transform processing on the encoding target image, and performs inverse wavelet transform processing based on the LH component and HL component obtained by the wavelet transform processing. The edge component may be extracted.

The image decoding apparatus according to another aspect of the present invention provides (k) a horizontal edge in which horizontal and vertical edge components are extracted from an encoding target image, and the horizontal edge components are projected in the horizontal direction. projection data and the vertical direction of the edge components and a vertical edge projection data projected vertically is decomposed into a set of first coefficient by the first orthogonal transformation processing, and the encoding target image, the first An image to be converted, which is obtained by performing a difference operation between the restored horizontal edge projection data based on the set of coefficients and the restored edge component based on the back projection of the restored vertical edge projection data, is decomposed into the second coefficients by the second orthogonal transformation process. The compressed data including the compressed code formed by encoding the first coefficient set and the second coefficient set is subjected to inverse encoding processing, and the first coefficient set and the second coefficient set of Decoding means and, (l) the first in a set of coefficients comprising performing a first inverse orthogonal transform is an inverse conversion process of the first orthogonal transform processing of the restored horizontal edge projection data for decoding the set of numbers And (m) an edge restoring means for generating a restored edge component formed by back projecting the restored horizontal edge projection data and the restored vertical edge projection data, n) a second inverse conversion means for generating a restoring conversion target image formed by subjecting the second inverse orthogonal transform processing is an inverse conversion process of the second orthogonal transform process to a set of said second coefficient, ( o) Image restoration means for generating a restored image obtained by adding the restoration conversion target image and the restored edge component.

In the image decoding method of the present invention, (k) horizontal edge projection data obtained by extracting horizontal and vertical edge components from the encoding target image and projecting the horizontal edge components in the horizontal direction and the vertical The vertical edge projection data in which the edge component of the direction is projected in the vertical direction is decomposed into a first set of coefficients by the first orthogonal transformation process, and is based on the encoding target image and the first set of coefficients. A conversion target image obtained by performing a difference operation with the restored edge component based on the back projection of the restored horizontal edge projection data and the restored vertical edge projection data is decomposed into second coefficients by the second orthogonal transformation process, and the first coefficient The decoding means performs a reverse encoding process on the compressed data including the compression code obtained by encoding the coefficient set and the second coefficient set, so that the first coefficient set and the second coefficient set are decoded. Person in charge A decoding step of decoding a set of, (l) first the first inverse transform unit is an inverse conversion process of the first orthogonal transform processing to the set of the first coefficient decoded by the decoding means A first inverse transform step for generating reconstructed horizontal edge projection data and reconstructed vertical edge projection data obtained by performing the inverse orthogonal transform process; and (m) edge reconstructing means, wherein An edge restoration step for generating a restored edge component formed by backprojecting data; and (n) an inverse transform process of the second orthogonal transform process on the second coefficient set decoded by the decoding means. a second inverse transformation step of generating a restoring conversion target image composed by performing inverse orthogonal transformation process of 2, is (o) the image restoring unit, by adding the above-mentioned restoring conversion target image and the restoration edge component That includes an image restoration step of generating a restored image.

Also, the image decoding program of the present invention is a computer that (k) horizontal edge projection data in which horizontal and vertical edge components are extracted from an encoding target image and the horizontal edge components are projected in the horizontal direction. And the vertical edge projection data obtained by projecting the vertical edge component in the vertical direction are decomposed into a first set of coefficients by the first orthogonal transformation process, and the encoding target image and the first coefficient The transformation target image obtained by performing the difference operation between the restored horizontal edge projection data based on the set and the restored edge component based on the back projection of the restored vertical edge projection data is decomposed into the second coefficient by the second orthogonal transformation process, The compressed data including the compressed code formed by encoding the first coefficient set and the second coefficient set is subjected to inverse encoding processing, and the first coefficient set and Decoding means for decoding a set of serial second coefficient, and subjected to a first inverse orthogonal transform is an inverse conversion process of the first orthogonal transform processing to the set of (l) the first coefficient restored First inverse transform means for generating horizontal edge projection data and restored vertical edge projection data; and (m) edge restoration for generating a restored edge component formed by back projecting the restored horizontal edge projection data and the restored vertical edge projection data. means and, (n) a second inverse transformation to generate the restoring conversion target image formed by subjecting the second inverse orthogonal transform processing is an inverse conversion process of the second orthogonal transform process to a set of said second coefficient And (o) image restoration means for generating a restored image formed by adding the restoration conversion target image and the restoration edge component.

  According to these inventions, the restored image of the encoding target image is faithfully reproduced based on the compressed data generated by the above-described image encoding device or the computer operated by the above-described image encoding program.

  According to the present invention, an image to be encoded can be decomposed into a small number of coefficients, so that an image encoding device, an image encoding method, and an image encoding program capable of realizing efficient encoding are provided. The

  An image decoding apparatus capable of faithfully reproducing a decoded image of an encoding target image based on compressed data generated by an image encoding apparatus of the present invention or a computer that operates according to the image encoding program of the present invention, A decoding method and an image decoding program are provided.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals.

  [First Embodiment]

  FIG. 1 is a diagram showing a configuration of an image encoding device 1 according to an embodiment of the present invention. The image encoding device 1 can be physically a computer including a CPU (Central Processing Unit), a storage device such as a memory, a display device such as a display, a communication device, and the like. The image encoding device 1 may be a mobile communication terminal such as a mobile phone. That is, a device capable of information processing can be widely applied to the image encoding device 1.

  As shown in FIG. 1, the image encoding device 1 functionally includes an edge extraction unit (edge extraction unit) 2, a projection unit (projection unit) 4, and a first conversion unit (first conversion unit). 6, a first inverse transform unit (corresponding to a part of the first inverse transform unit) 8, an edge restoration unit (corresponding to a part of the first inverse transform unit) 10, a residual component generation unit 12, The determination unit 14 includes a conversion target image generation unit (conversion target image generation unit) 18, a second conversion unit (second conversion unit) 20, and an encoding unit (encoding unit) 22.

  The edge extraction unit 2 extracts edge components in the horizontal direction and the vertical direction of the encoding target image. In this embodiment, in order to extract an edge component, the edge extraction unit 2 performs one-level two-dimensional DWT on the encoding target image. The edge extraction unit 2 removes the LL component and the HH component from the LL component, the LH component, the HL component, and the HH component generated by the one-level two-dimensional DWT, and converts the remaining LH component and HL component into two. Dimensional inverse DWT is applied. Thereby, the edge extraction unit 2 can obtain edge components in the horizontal direction and the vertical direction of the encoding target image. Note that the method for extracting an edge is not limited to a method using one-level two-dimensional DWT, and various methods can be used. For example, the edge extraction unit 2 may use a Canny Edge Detector.

  The projection unit 4 generates horizontal edge projection data by projecting the edge component extracted by the edge extraction unit 2 in the horizontal direction. The projecting unit 4 generates vertical edge projection data by projecting the edge component extracted by the edge extracting unit 2 in the vertical direction.

  The first conversion unit 6 decomposes the horizontal edge projection data and the vertical edge projection data into m wavelet coefficients, respectively, using a one-dimensional DWT. m is an integer of 1 or more that is N or less, which is arbitrarily determined. In general, processing for converting an image into projection data by projection processing is called radon transformation. The process of performing one-dimensional DWT on the projection data generated by the Radon transform is called a ridgelet transform. Therefore, in this specification, the wavelet coefficient generated by the first conversion unit 6 is referred to as a rigidlet coefficient.

  The 1st conversion part 6 produces | generates a quantized rigidlet coefficient by quantizing a rigidlet coefficient. The first conversion unit 6 increases m to the horizontal edge projection data and the vertical edge projection data to m quantized rigidlet coefficients until the determination unit 14 determines that a residual determination condition described later is satisfied. Disassembled into When the determination unit 14 determines that the residual determination condition is satisfied, the first conversion unit 6 outputs m quantized rigidlet coefficients at that time to the encoding unit 22.

  The first inverse transform unit 8 restores the rigidette coefficient by inversely quantizing the quantized rigidette coefficient generated by the first transform unit 6. The first inverse transform unit 8 generates a restored horizontal edge projection data obtained by restoring the horizontal edge projection data and a restored vertical edge projection data obtained by restoring the vertical edge projection data by performing a one-dimensional inverse DWT on the restored rigidlet coefficient. To do.

  The edge restoration unit 10 backprojects the restored horizontal edge projection data restored by the first inverse transformation unit 8 in the horizontal direction. Further, the edge restoration unit 10 back-projects the restored vertical edge projection data restored by the first inverse transform unit 8 in the vertical direction. The edge restoration unit 10 generates a restored edge component obtained by restoring the edge component of the encoding target image through these back projection processes.

  The residual component generation unit 12 generates a residual component by taking a difference between the edge component extracted by the edge extraction unit 2 and the restored edge component generated by the edge restoration unit 10.

  The determination unit 14 decomposes the difference between the restored edge component and the edge component based on the m quantized rigidlet coefficients, that is, the residual component, into N−m wavelet coefficients by two-dimensional DWT. The determination unit 14 quantizes the Nm wavelet coefficients to obtain quantized wavelet coefficients. The determination unit 14 restores the wavelet coefficients by inverse-quantizing the Nm quantized wavelet coefficients. The determination unit 14 generates a decoded residual component obtained by decoding the residual component by performing two-dimensional inverse DWT on the restored wavelet coefficient.

  The determination unit 14 performs MSE (Mean Square Error) of a combined component obtained by adding a restored edge component based on m quantized rigidlet coefficients and a decoding residual component based on Nm quantized wavelet coefficients, and an edge component. ) Is calculated while increasing m, and the minimum MSE is stored.

  The determination unit 14 has a minimum MSE of a combined component obtained by adding a restored edge component based on m + 1 quantized rigidlet coefficients and a decoding residual component based on N− (m + 1) wavelet coefficients, and an edge component. When the MSE is exceeded, it is assumed that the residual determination condition is satisfied, and the first transform unit 6 outputs m quantized rigidlet coefficients. In addition, when the residual determination condition is satisfied, the determination unit 14 outputs a restored edge component based on the m quantized rigidlet coefficients generated by the edge restoration unit 10 to the conversion target image generation unit 18.

  The conversion target image generation unit 18 generates a conversion target image by performing a difference operation between the encoding target image and the restored edge component output by the determination unit 14.

  The second conversion unit 20 decomposes the conversion target image generated by the conversion target image generation unit 18 into wavelet coefficients using a two-dimensional DWT. The second conversion unit 20 quantizes the wavelet coefficients and generates quantized wavelet coefficients. The second conversion unit 20 outputs the quantized wavelet coefficients to the encoding unit 22.

  The encoding unit 22 generates a compressed code by performing arithmetic encoding on the quantized rigidlet coefficients output by the first conversion unit 6 and the quantized wavelet coefficients output by the second conversion unit 20. The encoding unit 22 generates compressed data including the generated compression code.

  Hereinafter, the operation of the image encoding device 1 according to the present embodiment will be described. In addition, an image encoding method according to an embodiment of the present invention will be described. FIG. 2 is a flowchart of the image encoding method according to the embodiment.

  As shown in FIG. 2, in this image encoding method, the edge extraction unit 2 extracts edge components in the horizontal direction and the vertical direction of the encoding target image (step S01).

  Next, the projection unit 4 projects the edge component extracted by the edge extraction unit 2 in the horizontal direction to generate horizontal edge projection data, and projects the edge component in the vertical direction to generate vertical edge projection data (step). S02).

  Next, the first converter 6 performs one-dimensional DWT on each of the horizontal edge projection data and the vertical edge projection data, thereby decomposing each of the horizontal edge projection data and the vertical edge projection data into m rigidlet coefficients. Then, the first conversion unit 6 quantizes the m rigidlet coefficients to generate m quantized rigidlet coefficients (step S03).

  Next, the first inverse transform unit 8 inversely quantizes the m quantized rigidlet coefficients to restore the m rigidlet coefficients. The first inverse transform unit 8 generates restored horizontal edge projection data and restored vertical edge projection data by performing one-dimensional inverse DWT on the restored m rigidlet coefficients (step S04).

  Next, the edge restoration unit 10 back-projects the restored horizontal edge projection data in the horizontal direction, and back-projects the restored vertical edge projection data in the vertical direction to generate a restored edge component (step S05).

  Next, the residual component generation unit 12 determines a difference between the edge component extracted by the edge extraction unit 2 and the restored edge component restored by the edge restoration unit 10, thereby generating a residual component (step S06). ).

  Next, the determination unit 14 determines whether or not the above-described residual determination condition is satisfied (step S07). If the residual determination condition is not satisfied, m is increased, and processing from step S03 to step S06 is performed. Is done.

  On the other hand, when the residual determination condition is satisfied, the first conversion unit 6 outputs the quantized rigidette coefficient to the encoding unit 22, and the determination unit 14 converts the restored edge component generated by the edge restoration unit 10. The image is output to the target image generation unit 18.

  Next, the conversion target image generation unit 18 generates a conversion target image by performing a difference operation between the encoding target image and the restored edge component output by the determination unit 14 (step S08).

  Next, the second conversion unit 20 decomposes the conversion target image into wavelet coefficients by two-dimensional DWT. The second conversion unit 20 generates a quantized wavelet coefficient by quantizing the wavelet coefficient (step S09).

  Next, the encoding unit 22 generates a compression code by arithmetically encoding the quantized rigidlet coefficients output by the first conversion unit 6 and the quantized wavelet coefficients generated by the second conversion unit 20. The encoding unit 22 generates compressed data including this compression code (step S10).

  Hereinafter, an image encoding program 30 for causing a computer to operate as the image encoding apparatus 1 will be described. FIG. 3 is a diagram showing a configuration of the image encoding program 30. The image encoding program 30 is provided by a recording medium such as a CD-ROM, DVD, or ROM, or a semiconductor memory, for example. The image encoding program 30 may be provided via a network as a computer data signal superimposed on a carrier wave.

  The image encoding program 30 includes a main module 31 that controls processing, an edge extraction module 32, a projection module 34, a first conversion module 36, a first inverse conversion module 38, an edge restoration module 40, a residual, A component generation module 42, a determination module 44, a conversion target image generation module 46, a second conversion module 48, and an encoding module 50 are provided.

  Edge extraction module 32, projection module 34, first conversion module 36, first inverse conversion module 38, edge restoration module 40, residual component generation module 42, determination module 44, conversion target image generation module 46, second conversion module 48 The functions that the encoding module 50 realizes in the computer are the above-described edge extraction unit 2, projection unit 4, first conversion unit 6, first inverse conversion unit 8, edge restoration unit 10, residual component generation unit 12, determination The functions of the unit 14, the conversion target image generation unit 18, the second conversion unit 20, and the encoding unit 22 are the same.

  Hereinafter, operations and effects of the image encoding device 1 according to the present embodiment will be described. The image encoding device 1 generates horizontal projection edge data in which the horizontal edge component of the encoding target image is projected in the horizontal direction, and vertical edge projection data in which the vertical edge component is projected in the vertical direction. The The horizontal projection edge data and the vertical edge projection data are one-dimensional signals. Therefore, the horizontal projection edge data and the vertical edge projection data can be decomposed into a small number of coefficients by the one-dimensional DWT. That is, in the two-dimensional DWT, a large number of coefficients are required to decompose an edge extending in the one-dimensional direction. However, by converting the edge component into projection data that is a one-dimensional signal, it can be decomposed into a small number of coefficients. It becomes.

  In addition, a one-dimensional edge extending in the horizontal direction and the vertical direction is removed from the conversion target image obtained by removing the restoration edge component from the encoding target image. Therefore, the conversion target image can be decomposed into a small number of coefficients by the two-dimensional DWT. As described above, the image encoding device 1 can decompose the encoding target image into a small number of coefficients, and thus can efficiently encode the encoding target image.

  The image encoding device 1 according to the embodiment of the present invention has been described above. However, the idea of the present invention applied to the image encoding device 1 is not limited to still image encoding, but also to moving image encoding. Can also be applied. In encoding a moving image, a difference calculation is performed between a predicted image of a coding target frame generated by motion compensated prediction for a reference image and the coding target frame. A prediction residual image is generated by this difference calculation. For example, the present invention can be used for encoding the prediction residual image.

  [Second Embodiment]

  FIG. 4 is a diagram showing a configuration of the image decoding device 60 according to the embodiment of the present invention. The image decoding device 60 is a device that restores an image from the compressed data generated by the image encoding device 1. The image decoding device 60 can physically be a computer including a CPU (Central Processing Unit), a storage device such as a memory, a display device such as a display, a communication device, and the like. The image decoding device 60 may be a mobile communication terminal such as a mobile phone. That is, a device capable of information processing can be widely applied to the image decoding device 60.

  As shown in FIG. 4, the image decoding device 60 functionally includes a decoding unit (decoding unit) 62, a first inverse transformation unit (first inverse transformation unit) 64, and an edge restoration unit (edge restoration unit). ) 66, a second inverse transform unit (second inverse transform unit) 68, and an image restoration unit (image restoration unit) 70.

Decoding unit 62, by inverse arithmetic coding compression code included in the compressed data generated by the image encoding device 1, decodes the quantized Rijiretto coefficients and quantized wavelet coefficients.

  The first inverse transform unit 64 degenerates the quantized rigidette coefficient decoded by the decoding unit 62 to generate a rigidlet coefficient. The first inverse transform unit 64 generates a restored horizontal edge projection data obtained by restoring the horizontal edge projection data and a restored vertical edge projection data obtained by restoring the vertical edge projection data by performing a one-dimensional inverse DWT on the generated rigidette coefficient. To do.

  The edge restoration unit 66 back-restores the restored horizontal edge projection data in the horizontal direction, and back-projects the restored vertical edge projection data in the vertical direction, thereby generating a restored edge component.

  The second inverse transform unit 68 performs a two-dimensional inverse DWT on the wavelet coefficients decoded by the decoding unit 62, thereby generating a restored conversion target image in which the conversion target is restored.

  The image restoration unit 70 is encoded by the image encoding device 1 by adding the restoration edge component generated by the edge restoration unit 66 and the restoration conversion target image generated by the second inverse transformation unit 68. A restored image obtained by restoring the image is generated.

  Hereinafter, the operation of the image decoding device 60 according to the present embodiment will be described. In addition, an image decoding method according to the embodiment of the present invention will be described. FIG. 5 is a flowchart of the image decoding method according to the embodiment.

  As shown in FIG. 5, in this image decoding method, the decoding unit 62 performs inverse arithmetic coding on the compression code included in the compressed data generated by the image coding device 1, and produces a quantized rigidlet coefficient and quantization. The wavelet coefficient is decoded (step S21).

  Next, the first inverse transform unit 64 generates the rigidette coefficient by inversely quantizing the quantized rigidette coefficient decoded by the decoding unit 62. Then, the first inverse transform unit 64 generates restored horizontal edge projection data and restored vertical edge projection data by performing one-dimensional inverse DWT on the generated rigidette coefficients (step S22).

  Next, the edge restoration unit 66 back-projects the restored horizontal edge projection data in the horizontal direction and back-projects the restored vertical edge projection data in the vertical direction to generate a restored edge component (step S23).

  Next, the second inverse transformation unit 68 generates a restoration transformation target image by performing two-dimensional inverse DWT on the wavelet coefficients decoded by the decoding unit 62 (step S24).

  Next, the image restoration unit 70 generates a restored image by adding the restored edge component and the restoration conversion target image (step S25). Through the above processing, the image encoded by the image encoding device 1 is restored.

  Hereinafter, an image decoding program 80 for causing a computer to operate as the image decoding device 60 will be described. FIG. 6 is a diagram showing the configuration of the image decoding program 80. The image decoding program 80 is provided by a recording medium such as a CD-ROM, a DVD, or a ROM, or a semiconductor memory, for example. The image decoding program 80 may be provided via a network as a computer data signal superimposed on a carrier wave.

  The image decoding program 80 includes a main module 81 that supervises processing, a decoding module 82, a first inverse transform module 84, an edge restoration module 86, a second inverse transformation module 88, and an image restoration module 90.

  The decoding module 82, the first inverse conversion module 84, the edge restoration module 86, the second inverse transformation module 88, and the image restoration module 90 have the functions realized by the computer in the above-described decoding unit 62, first inverse transformation unit 64, edge restoration The functions of the unit 66, the second inverse transform unit 68, and the image restoration unit 70 are the same.

  Hereinafter, operations and effects of the image decoding device 60 according to the present embodiment will be described. In the image decoding device 60, the compression code included in the compressed data generated by the image encoding device 1 is decoded by inverse arithmetic coding. By this decoding, quantized rigidlet coefficients and quantized wavelet coefficients are generated. A quantized rigidlet coefficient is subjected to inverse quantization, one-dimensional inverse DWT processing, and further back projection processing, whereby a restored edge component is generated. The quantized wavelet coefficient undergoes inverse quantization and two-dimensional inverse DWT processing to generate a restoration transformation target image. By adding the restoration conversion target image and the restoration edge component, a restored image obtained by restoring the image encoded by the image encoding device 1 is generated. As described above, the image decoding device 60 can faithfully restore the image encoded by the image encoding device 1.

FIG. 1 is a diagram illustrating a configuration of an image encoding device according to an embodiment of the present invention. FIG. 2 is a flowchart of the image encoding method according to the embodiment of the present invention. FIG. 3 is a diagram showing a configuration of an image encoding program according to the embodiment of the present invention. FIG. 4 is a diagram showing the configuration of the image decoding apparatus according to the embodiment of the present invention. FIG. 5 is a flowchart of the image decoding method according to the embodiment of the present invention. FIG. 6 is a diagram showing a configuration of an image decoding program according to the embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Image coding apparatus, 2 ... Edge extraction part, 4 ... Projection part, 6 ... 1st conversion part, 8 ... 1st inverse transformation part, 10 ... Edge restoration part, 12 ... Residual component generation part, 14 ... Determination , 18 ... conversion target image generation unit, 20 ... second conversion unit, 22 ... encoding unit, 60 ... image decoding device, 62 ... decoding unit, 64 ... first inverse conversion unit, 66 ... edge restoration unit, 68 ... Second inverse transform unit, 70... Image restoration unit.

Claims (10)

Edge extraction means for extracting edge components in the horizontal and vertical directions of the encoding target image;
Projection means for generating horizontal edge projection data obtained by projecting the edge component in a horizontal direction, and vertical edge projection data obtained by projecting the edge component in a vertical direction;
First transforming means for generating a first set of coefficients obtained by subjecting each of the horizontal edge projection data and the vertical edge projection data to a first orthogonal transform process;
First inverse transforming means for generating restored horizontal edge projection data and restored vertical edge projection data by performing a first inverse transform process that is an inverse transform process of the first orthogonal transform process on the first set of coefficients. When,
Conversion target image generating means for generating a conversion target image by performing a difference operation between the encoding target image and the restored edge component based on the back projection of the restored horizontal edge projection data and the restored vertical edge projection data ;
Second transforming means for generating a second set of coefficients obtained by subjecting the transform target image to a second orthogonal transform process;
Encoding means for generating a compressed data including a compression code formed by performing coding processing to the set of the set and a second coefficient of the first coefficient,
An image encoding device comprising:   The edge extraction unit performs one-level wavelet transform processing on the encoding target image, and extracts the edge component by inverse wavelet transform processing based on LH components and HL components obtained by the wavelet transform processing. The image encoding apparatus according to claim 1. An edge extracting step in which the edge extracting means extracts edge components in the horizontal and vertical directions of the encoding target image;
Projection means for generating horizontal edge projection data obtained by projecting the edge component in the horizontal direction, and generating vertical edge projection data obtained by projecting the edge component in the vertical direction;
A first conversion step in which a first conversion unit generates a first set of coefficients obtained by performing a first orthogonal transformation process on each of the horizontal edge projection data and the vertical edge projection data;
A first inverse transform unit performs a first inverse transform process that is an inverse transform process of the first orthogonal transform process on the first set of coefficients to obtain restored horizontal edge projection data and restored vertical edge projection data. A first inverse transformation step to generate;
Is converted image generating means, for generating said coded image, the converted image formed by performing a difference operation between the restoration horizontal edge projection data and the restoration vertical edge recovery edge component based on back projection of the projection data conversion A target image generation step;
A second transforming step, wherein a second transforming unit generates a second set of coefficients obtained by subjecting the transform target image to a second orthogonal transform process;
An encoding step for generating compressed data including a compression code obtained by performing an encoding process on the first coefficient set and the second coefficient set;
An image encoding method including: Computer
Edge extraction means for extracting edge components in the horizontal and vertical directions of the encoding target image;
Projection means for generating horizontal edge projection data obtained by projecting the edge component in a horizontal direction, and vertical edge projection data obtained by projecting the edge component in a vertical direction;
First transforming means for generating a first set of coefficients obtained by subjecting each of the horizontal edge projection data and the vertical edge projection data to a first orthogonal transform process;
First inverse transforming means for generating restored horizontal edge projection data and restored vertical edge projection data by performing a first inverse transform process that is an inverse transform process of the first orthogonal transform process on the first set of coefficients. When,
Conversion target image generating means for generating a conversion target image by performing a difference operation between the encoding target image and the restored edge component based on the back projection of the restored horizontal edge projection data and the restored vertical edge projection data ;
Second transforming means for generating a second set of coefficients obtained by subjecting the transform target image to a second orthogonal transform process;
Encoding means for generating compressed data including a compression code obtained by performing an encoding process on the first coefficient set and the second coefficient set;
An image encoding program for functioning as Horizontal edge projection data in which horizontal and vertical edge components are extracted from the encoding target image, the horizontal edge components are projected in the horizontal direction, and vertical edges in which the vertical edge components are projected in the vertical direction and projection data are decomposed into a set of first coefficient by the first orthogonal transformation process, the the encoding target image, the first coefficient restored horizontal edge projection data and reverse recovery vertical edge projection data based on the set of A transformation target image obtained by performing a difference operation with a restored edge component based on projection is decomposed into second coefficients by a second orthogonal transformation process, and the first coefficient set and the second coefficient set are encoded. Decoding means for decoding the first coefficient set and the second coefficient set by performing a reverse encoding process on the compressed data including the compressed code formed by
First inverse generating a restored horizontal edge projection data and restore vertical edge projection data formed by performing a first inverse orthogonal transform is an inverse conversion process of the first orthogonal transform processing to said set of first coefficient Conversion means;
Edge restoration means for generating a restored edge component formed by back projecting the restored horizontal edge projection data and the restored vertical edge projection data;
Second inverse transforming means for generating a restoration transform target image obtained by performing a second inverse orthogonal transform process that is an inverse transform process of the second orthogonal transform process on the second coefficient set;
Image restoration means for generating a restored image formed by adding the restoration conversion target image and the restored edge component;
An image decoding apparatus comprising: Horizontal edge projection data in which horizontal and vertical edge components are extracted from the encoding target image, the horizontal edge components are projected in the horizontal direction, and vertical edges in which the vertical edge components are projected in the vertical direction and projection data are decomposed into a set of first coefficient by the first orthogonal transformation process, the the encoding target image, the first coefficient restored horizontal edge projection data and reverse recovery vertical edge projection data based on the set of A transformation target image obtained by performing a difference operation with a restored edge component based on projection is decomposed into second coefficients by a second orthogonal transformation process, and the first coefficient set and the second coefficient set are encoded. A decoding step for decoding the first coefficient set and the second coefficient set by performing a reverse encoding process on the compressed data including the compressed code formed by the decoding unit;
A restored horizontal edge formed by a first inverse transform unit performing a first inverse orthogonal transform process, which is an inverse transform process of the first orthogonal transform process, on the first set of coefficients decoded by the decoding unit A first inverse transform step for generating projection data and reconstructed vertical edge projection data;
An edge restoration step in which an edge restoration means generates a restored edge component formed by back projecting the restored horizontal edge projection data and the restored vertical edge projection data;
A second inverse that generates a restored transformation target image obtained by performing a second inverse orthogonal transform process that is an inverse transform process of the second orthogonal transform process on the second coefficient set decoded by the decoding means. A conversion step ;
An image restoration step, wherein the image restoration means generates a restored image formed by adding the restoration conversion target image and the restored edge component;
An image decoding method including: Computer
Horizontal edge projection data in which horizontal and vertical edge components are extracted from the encoding target image, the horizontal edge components are projected in the horizontal direction, and vertical edges in which the vertical edge components are projected in the vertical direction Projection data is decomposed into a first set of coefficients by a first orthogonal transform process, and the inverse of the restored horizontal edge projection data and the restored vertical edge projection data based on the encoding target image and the first set of coefficients. A transformation target image obtained by performing a difference operation with a restored edge component based on projection is decomposed into second coefficients by a second orthogonal transformation process, and the first coefficient set and the second coefficient set are encoded. Decoding means for decoding the first coefficient set and the second coefficient set by performing a reverse encoding process on the compressed data including the compressed code formed by
First inverse generating a restored horizontal edge projection data and restore vertical edge projection data formed by performing a first inverse orthogonal transform is an inverse conversion process of the first orthogonal transform processing to said set of first coefficient Conversion means;
Edge restoration means for generating a restored edge component formed by back projecting the restored horizontal edge projection data and the restored vertical edge projection data;
Second inverse transforming means for generating a restoration transform target image obtained by performing a second inverse orthogonal transform process that is an inverse transform process of the second orthogonal transform process on the second coefficient set;
Image restoration means for generating a restored image formed by adding the restoration conversion target image and the restored edge component;
Decoding program for functioning as   Horizontal edge projection data in which horizontal and vertical edge components are extracted from the encoding target image and the horizontal edge components are projected in the horizontal direction and vertical edges in which the vertical edge components are projected in the vertical direction Projection data is decomposed into a first set of coefficients by a first transformation process, and back projection of restored horizontal edge projection data and restored vertical edge projection data based on the encoding target image and the first set of coefficients. The conversion target image obtained by performing the difference operation with the restored edge component based on the above is decomposed into second coefficients by the second conversion process, and the first coefficient set and the second coefficient set are encoded. Decoding means for decoding the first coefficient set and the second coefficient set by performing a reverse encoding process on the compressed data including the compressed code comprising:
  First inverse transform means for generating restored horizontal edge projection data and restored vertical edge projection data obtained by subjecting the first set of coefficients to a first inverse transform process that is an inverse transform process of the first transform process. When,
  Edge restoration means for generating a restored edge component formed by back projecting the restored horizontal edge projection data and the restored vertical edge projection data;
  Second inverse transformation means for generating a restoration transformation target image obtained by performing a second inverse transformation process, which is an inverse transformation process of the second transformation process, on the second coefficient set;
  Image restoration means for generating a restored image formed by adding the restoration conversion target image and the restored edge component;
An image decoding apparatus comprising:   Horizontal edge projection data in which horizontal and vertical edge components are extracted from the encoding target image and the horizontal edge components are projected in the horizontal direction and vertical edges in which the vertical edge components are projected in the vertical direction Projection data is decomposed into a first set of coefficients by a first transformation process, and back projection of restored horizontal edge projection data and restored vertical edge projection data based on the encoding target image and the first set of coefficients. The conversion target image obtained by performing the difference operation with the restored edge component based on the above is decomposed into second coefficients by the second conversion process, and the first coefficient set and the second coefficient set are encoded. A decoding step in which decoding means performs a reverse encoding process on the compressed data including the compressed code, and decodes the first coefficient set and the second coefficient set;
  Reconstructed horizontal edge projection data in which a first inverse transform means performs a first inverse transform process that is an inverse transform process of the first transform process on the first set of coefficients decoded by the decoding means. And a first inverse transform step for generating reconstructed vertical edge projection data;
  An edge restoration step in which an edge restoration means generates a restored edge component formed by back projecting the restored horizontal edge projection data and the restored vertical edge projection data;
  A second inverse transformation step of generating a restored transformation target image obtained by performing a second inverse transformation process which is an inverse transformation process of the second transformation process on the second coefficient set decoded by the decoding means; When,
  An image restoration step, wherein the image restoration means generates a restored image formed by adding the restoration conversion target image and the restored edge component;
An image decoding method including:   Computer
  Horizontal edge projection data in which horizontal and vertical edge components are extracted from the encoding target image and the horizontal edge components are projected in the horizontal direction and vertical edges in which the vertical edge components are projected in the vertical direction Projection data is decomposed into a first set of coefficients by a first transformation process, and back projection of restored horizontal edge projection data and restored vertical edge projection data based on the encoding target image and the first set of coefficients. The conversion target image obtained by performing the difference operation with the restored edge component based on the above is decomposed into second coefficients by the second conversion process, and the first coefficient set and the second coefficient set are encoded. Decoding means for decoding the first coefficient set and the second coefficient set by performing a reverse encoding process on the compressed data including the compressed code comprising:
  First inverse transform means for generating restored horizontal edge projection data and restored vertical edge projection data obtained by subjecting the first set of coefficients to a first inverse transform process that is an inverse transform process of the first transform process. When,
  Edge restoration means for generating a restored edge component formed by back projecting the restored horizontal edge projection data and the restored vertical edge projection data;
  Second inverse transformation means for generating a restoration transformation target image obtained by performing a second inverse transformation process, which is an inverse transformation process of the second transformation process, on the second coefficient set;
  Image restoration means for generating a restored image formed by adding the restoration conversion target image and the restored edge component;
Decoding program for functioning as

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