JP4753006B2 - Image encoding apparatus, image decoding apparatus, and programs thereof - Google Patents

Description

  The present invention relates to an image encoding device that encodes binary images of various densities.

  In the text area defined by JBIG2, partial images (symbols) are registered as a dictionary. This symbol is expressed by a dictionary index and position. When text region encoding is applied to binary halftone image data, a typical halftone dot pattern is registered as a symbol.

In a binary halftone dot image, a block of black pixels continuously forms a halftone dot. These halftone dots are easily cut out as one symbol when the black pixels constituting the halftone dots are separated from the black pixels constituting the other halftone dots.
However, in the region where the halftone dot density is high, the black pixels constituting the halftone dots are continuous with the black pixels constituting the other halftone dots, and it is difficult to appropriately cut out each halftone dot.
For this reason, symbols are registered in a dictionary as symbols including a plurality of halftone dots, and when this dictionary is used, it cannot be expected to be compressed at a high compression rate.

In Patent Document 1, a method of encoding graphic data by storing symbols in a dictionary is disclosed, but in this method, in addition to position information and symbol information, color information (CLUT conversion table or the like) is disclosed. ) Is stored in the dictionary, so encoding is not performed efficiently.
JP 2000-101446 A

  The present invention has been made from the above-described background, and an object thereof is to provide an image encoding device and an image decoding device capable of compressing a binary halftone image at a high compression rate.

In order to achieve the above object, a first image encoding device according to the present invention includes an input means for inputting an input image including a binary halftone dot pattern and features of the binary halftone dot pattern, and the input means. Screen processing is performed on the input image input by step (b) to extract the characteristics of the binary halftone dot pattern, and based on the features of the binary halftone dot pattern extracted by the halftone dot feature extraction means. And a dictionary creating means for creating a dictionary for identifying a binary halftone dot pattern, and an encoding means for coding an input image based on the dictionary created by the dictionary creating means.

Preferably, the encoding means encodes the input image by text region encoding defined in JBIG2 based on the dictionary created by the dictionary creating means.
Preferably, the input means inputs an input image including at least one of the period, phase, shape and size of the binary halftone dot pattern as a characteristic of the binary halftone dot pattern.
Preferably, the encoding means encodes the identification information for identifying the binary halftone dot pattern and the position where the binary halftone dot pattern appears in the input image in association with each other.

The second image encoding apparatus according to the present invention performs screen processing on an input image including a binary halftone dot pattern and extracts features of the binary halftone dot pattern; A dictionary creating means for creating a dictionary for identifying the binary halftone dot pattern based on the extracted binary halftone dot pattern characteristics, and an input image is encoded based on the dictionary created by the dictionary creating means. Encoding means.

Preferably, the extraction unit extracts at least one of the period, phase, shape, and size of the binary halftone dot pattern.
Preferably, the encoding means encodes the identification information for identifying the binary halftone dot pattern and the position where the binary halftone dot pattern appears in the input image in association with each other.

An image decoding apparatus according to the present invention inputs an input image including a binary halftone dot pattern and features of the binary halftone dot pattern, and performs a screen process on the input image to extract a binary halftone dot pattern And a decoding means for decoding the code data based on code data generated by encoding an input image based on the dictionary, and creating a dictionary for identifying a binary halftone dot pattern based on the characteristics of And an image generation means for generating a decoded image using a decoding result by the decoding means and a dictionary.

Preferably, the decoding means decodes the binary halftone dot pattern identification information and the position where the binary halftone dot pattern appears in the input image.
Preferably, the image generating means further uses the identification information of the binary halftone dot pattern decoded by the decoding means and the position at which the binary halftone dot pattern appears in the input image, to obtain a decoded image. Generate.

A first program according to the present invention includes: an input step of inputting an input image including a binary halftone dot pattern and features of the binary halftone dot pattern in an image encoding device including a computer; and the input input A halftone dot feature extracting step for performing screen processing on the image and extracting features of the binary halftone dot pattern, and a dictionary for identifying the binary halftone dot pattern based on the extracted binary halftone dot pattern features And a coding step for coding an input image based on the created dictionary.

In addition, the second program according to the present invention is an extraction step of performing screen processing on an input image including a binary halftone dot pattern and extracting features of the binary halftone dot pattern in an image encoding device including a computer. A dictionary creating step for creating a dictionary for identifying the binary dot pattern based on the extracted binary dot pattern features; and a code for encoding the input image based on the created dictionary To the computer of the image encoding device.

Furthermore, a third program according to the present invention inputs an input image including a binary halftone dot pattern and features of the binary halftone dot pattern in an image decoding device including a computer, and performs screen processing on the input image. Based on the characteristics of the binary halftone dot pattern extracted by applying a dictionary for identifying the binary halftone dot pattern, based on the code data generated by encoding the input image based on this dictionary, The computer of the image decoding apparatus is caused to execute a decoding step for decoding the code data, an image generation step for generating a decoded image using the decoded result, and a dictionary.

  According to the image encoding device of the present invention, a binary halftone image can be compressed at a high compression rate.

First, in order to help understanding of the present invention, its background and outline will be described.
As a binary image encoding method, JBIG2 halftone region encoding has been proposed.
1A and 1B are diagrams for explaining a halftone area encoding process. FIG. 1A illustrates a binary image to be encoded, and FIG. 1B illustrates a halftone area encoding process. FIG. 1C illustrates code data generated using the image dictionary and its decoded image.
As illustrated in FIG. 1A, a binary image element (in this example, a character image “A”) is composed of a plurality of halftone dot patterns corresponding to density values (tone values), and is simulated. Is expressed in gradation. The size of the halftone dot pattern corresponds to the density value. In this example, since the character image “A” has a uniform density, a halftone dot pattern of a uniform size constitutes the character image “A”. In the halftone area encoding process of JBIG2, these binary halftone dot patterns are registered in the image dictionary in association with the density values, and a binary image composed of the halftone dot patterns is encoded.

As illustrated in FIG. 1B, when a plurality of halftone dot patterns having different sizes exist in the input image, each halftone dot pattern is associated with an index (density value) and registered in the image dictionary. Is done. This index is identification information for uniquely identifying each halftone dot pattern, and is a density value in this example.
When an input image is encoded using this image dictionary, code data as illustrated in FIG. 1C is generated. The code data is composed of density values (that is, indexes) of respective regions in the input image and position information (grid-like positions) indicating positions where the density values exist.
Then, the code data is decoded, and an image dictionary is referred to generate a decoded image. Specifically, based on the density value decoded from the code data, a halftone dot pattern registered in the image dictionary is selected, and the selected halftone dot pattern corresponds to the position information decoded from the code data. And a decoded image is generated.

FIG. 2 is a diagram illustrating an image dictionary and a decoded image when a binary input image having an edge is encoded by a halftone region encoding process.
As illustrated in FIG. 2, the input image is multi-valued with lower resolution, and the density value is registered in the image dictionary as a binary halftone dot pattern. When the input image is encoded by the halftone area encoding process, the edge information of the character image “A” may be lost in the decoded image.

  In JBIG2, text area encoding has been proposed. In the text region encoding process, a typical image pattern (symbol) appearing in an input image is registered in an image dictionary (symbol dictionary) in association with an index for identifying the image pattern, and this symbol dictionary is used, Encode the input image. When text region encoding is applied to a halftone image, each halftone image (halftone image having edge information) existing in the edge region of the input image is registered in the symbol dictionary as a halftone pattern. A decoded image holding the edge information is obtained. For this reason, the text area encoding process can prevent image quality deterioration more than the halftone area encoding process.

3A and 3B are diagrams for explaining the text region encoding process. FIG. 3A illustrates the case where the input image has a low density, and FIG. 3B illustrates the case where the input image has a high density. Is illustrated.
As illustrated in FIG. 3A, in the text region encoding process, all halftone dot patterns included in the input image are registered in the symbol dictionary. When the input image has a low density, the respective halftone dot patterns are separated from each other, and thus are recognized as individual halftone dot patterns. When a halftone dot pattern is registered in the symbol dictionary, an index is assigned to each halftone dot pattern. The halftone dot pattern is uniquely identified by the assigned index. The input image is encoded by text region encoding by associating an index with a position where a symbol to which the index is added appears in the input image.
As illustrated in FIG. 3B, when the input image has a high density, the halftone dot pattern is composed of a continuous halftone dot pattern and a black pixel. In this case, the halftone dot pattern can be registered in the symbol dictionary as one large block.

[Image processing device]
FIG. 4 is a diagram illustrating an encoding process by the image processing apparatus 2 according to the present invention.
As shown in FIG. 4, when a binary input image including a binary halftone dot pattern is input, the image processing apparatus 2 creates a symbol dictionary based on the characteristics of the halftone dot pattern. The characteristics of the halftone dot pattern are included in the input image data, and are, for example, at least one of the period, phase, shape, and size of the halftone dot pattern. The image processing device 2 associates identification information (index) for identifying a halftone dot pattern with a position where the binary halftone dot pattern appears in the input image based on the created symbol dictionary, Encoding is performed by encoding to generate code data. Further, the image processing apparatus 2 creates a symbol dictionary by extracting the features of the halftone dot pattern even when the features of the halftone dot pattern are not included in the input image.
For this reason, the image processing apparatus 2 can efficiently encode a high-resolution halftone image (2400 dpi to 9600 dpi) with high image quality.

[First Embodiment]
An image processing apparatus 2 according to the first embodiment of the present invention will be described.

[Hardware configuration]
A hardware configuration of the image processing apparatus 2 in the present embodiment will be described.
FIG. 5 is a diagram illustrating a hardware configuration of the image processing apparatus 2 to which the encoding method and the decoding method according to the present invention are applied, centering on the control apparatus 20. The image encoding device and the image decoding device according to the present invention are realized by the image processing device 2.
As illustrated in FIG. 5, the image processing apparatus 2 includes a control device 20 including a CPU 202 and a memory 204, a communication device 22, a recording device 24 such as an HDD / CD device, an LCD display device or a CRT display device, and a keyboard. A user interface device (UI device) 26 including a touch panel and the like is included.
The image processing apparatus 2 is a general-purpose computer in which, for example, an encoding program 4 and a decoding program 5 described later are installed as a part of a printer driver, and acquires image data via the communication apparatus 22 or the recording apparatus 24. The obtained image data is encoded or decoded and transmitted to the printer apparatus 10. Further, the image processing apparatus 2 may acquire image data optically read by the scanner function of the printer apparatus 10 and encode the acquired image data.

[Encoding program]
FIG. 6 is a diagram illustrating a functional configuration of the first encoding program 4 which is executed by the control device 20 (FIG. 5) and realizes the encoding method according to the present invention.
As illustrated in FIG. 6, the encoding program 4 includes a raster generation unit 400, a symbol dictionary creation unit 402, a symbol position generation unit 404, and an encoding unit 406.
Note that all or some of the functions of the encoding program 4 may be realized by an ASIC provided in the printer apparatus 10 or the like.

In the encoding program 4, the raster generation unit 400 uses a PDL (Page acquired through the communication device 22 or the recording device 24).
Enter the input image data in the Description Language format. The input image data includes a binary input image including a binary halftone dot pattern and features of the binary halftone dot pattern. The characteristic of the binary halftone dot pattern is a parameter relating to screen processing, and is at least one of the period, phase, shape, and size of the binary halftone dot pattern, for example. These parameters will be described later. In this way, the raster generation unit 400 constitutes an input unit that includes a binary halftone dot pattern and the characteristics of this binary halftone dot pattern.

  The raster generation unit 400 converts the input image into raster data (color component image) of each color component, and outputs it to the symbol dictionary creation unit 402 and the symbol position generation unit 404. The raster generation unit 400 outputs the characteristics of the binary halftone dot pattern included in the input image data to the symbol dictionary creation unit 402. Hereinafter, the binary halftone dot pattern may be abbreviated as a halftone dot pattern.

The symbol dictionary creation unit 402 creates a symbol dictionary to be applied to the encoding process of the input image based on the period of the binary halftone dot pattern input from the raster generation unit 400 and the symbol position generation unit 404 Output.
More specifically, the symbol dictionary creation unit 402, based on the period, phase, shape, and size of the halftone dot pattern input from the raster generation unit 400, from the input image, a halftone dot pattern ( Symbol). Further, the symbol dictionary creation unit 402 gives an index for identifying each symbol to the extracted symbols. That is, the symbol dictionary creation unit 402 creates a symbol dictionary by associating an index with a symbol. The index is, for example, identification information generated individually for each input image, and may be a serial number assigned to the symbol in the order in which the symbol is extracted from the input image. In this manner, the symbol dictionary creation unit 402 constitutes a dictionary creation unit that creates a dictionary for identifying a binary halftone dot pattern.

  The symbol position generation unit 404 compares a symbol registered in the symbol dictionary with a halftone dot pattern included in each color component image, identifies a halftone dot pattern that matches or resembles any symbol, and this halftone dot Symbol / position correspondence data for associating the index corresponding to the pattern with the position information of the halftone dot pattern is generated. The symbol position generation unit 404 outputs the generated symbol / position correspondence data to the encoding unit 406.

The encoding unit 406 generates code data by encoding the symbol / position correspondence data generated by the symbol position generation unit 404 by text region encoding specified in JBIG2, and generates the code data in the recording device 24 (FIG. 5) or output to the printer 10 or the like. Furthermore, the encoding unit 406 may encode the symbol dictionary by entropy encoding (Huffman encoding, arithmetic encoding, LZ encoding, or the like).
In this manner, the symbol position generation unit 404 and the encoding unit 406 constitute an encoding unit that encodes an input image based on the created symbol dictionary.

FIG. 7 is a diagram for explaining the characteristics of a halftone dot pattern used in creating a symbol dictionary.
As shown in FIG. 7, the feature of the halftone dot pattern is a value representing a screen unit area used in a preprocessed screen process, and includes at least one of the period, phase, shape, and size of the halftone dot pattern. . The screen unit area has, for example, a 5 × 5 matrix shape and size. The shape of the screen unit region may be a shape that can be periodically arranged, for example, at an angle of 45 degrees with respect to the main scanning direction. The position of the screen unit area is specified by the phase and period in the figure. For this reason, even when the halftone dot pattern is configured continuously with the black pixels of the halftone dot pattern adjacent to the black pixels, the symbol dictionary creation unit 402 (FIG. 6) is based on the features of the halftone dot patterns. A halftone dot pattern can be appropriately extracted and registered in the symbol dictionary as a symbol.

8A and 8B are diagrams for explaining a binary halftone dot pattern encoding process. FIG. 8A illustrates a high-density input image, and FIG. 8B illustrates symbols created from the input image. FIG. 8C illustrates a symbol / position correspondence data generated from an input image.
As illustrated in FIG. 8A, the input image includes a plurality of halftone dot patterns, and the high-density halftone dot pattern is continuously formed with the black pixels of the halftone dot pattern adjacent to the black pixels. The
As illustrated in FIG. 8B, the symbol dictionary creation unit 402 registers the extracted symbols in the symbol dictionary, and assigns an index (identification information) for identifying these symbols to each symbol. Complete the symbol dictionary.
As illustrated in FIG. 8C, the symbol position generation unit 404 compares the registered symbol with the halftone dot pattern included in each color component image of the input image to generate symbol / position correspondence data. . The encoding unit 406 encodes the symbol / position correspondence data generated by the symbol position generation unit 404 by text region encoding defined in JBIG2.

[Code data]
FIG. 9 is a diagram illustrating code data generated by the encoding program 4 (FIG. 6).
As illustrated in FIG. 9, the encoded data includes a header including data attribute information and the like, a created symbol dictionary, and an index and position information associated with each other and encoded by text region encoding. Contains data.

[Encoding operation]
FIG. 10 is a flowchart showing the encoding process (S10) by the encoding program 4.
As shown in FIG. 10, in step 100 (S100), when the PDL file is input as an input image, the raster generation unit 400, based on the input PDL file, the period, phase, shape and halftone dot pattern. The size is acquired and output to the symbol dictionary creation unit 402. The raster generation unit 400 converts the input image data into a color component image and outputs the color component image to the symbol dictionary creation unit 402 and the symbol position generation unit 404.

  In step 102 (S102), the symbol dictionary creation unit 402 extracts a halftone dot pattern that appears in each color component image based on the period, phase, shape, and size of the halftone dot pattern input from the raster generation unit 400. And register it as a symbol in the symbol dictionary. Furthermore, the symbol dictionary creation unit 402 creates an index dictionary by assigning an index for identifying each extracted symbol.

  In step 104 (S104), the symbol position generation unit 404 uses the symbol dictionary in each color component image to identify a halftone dot pattern that matches or is similar to the symbol, an index corresponding to the symbol, and the halftone dot pattern. Symbol / position correspondence data for associating with the position where the symbol appears is generated.

In step 106 (S106), the encoding unit 406 encodes the symbol / position correspondence data generated by the symbol position generation unit 404 by text region encoding defined in JBIG2.
In step 108 (S108), the encoding unit 406 generates code data shown in FIG. 9 from the encoded data, and outputs the code data to the printer device 10 or the like.

[Decryption program]
FIG. 11 is a diagram illustrating a functional configuration of the decoding program 5 which is executed by the control device 20 (FIG. 5) and implements the image decoding method according to the present invention.
As illustrated in FIG. 11, the decoding program 5 includes a decoding processing unit 500 and a decoded image generation unit 502. Note that all or some of the functions of the decryption program 5 may be realized by an ASIC provided in the printer apparatus 10 or the like.

  In the decoding program 5, the decoding processing unit 500 receives an input image including the binary halftone dot pattern and the characteristics of the binary halftone dot pattern, and the binary network included in the input image. A dictionary for identifying a binary halftone dot pattern is created based on the characteristics of the point pattern, and the code data is generated by decoding the text area based on the code data generated by encoding the input image based on the dictionary. Decrypt. The decoding processing unit 500 outputs the decoded result to the decoded image generation unit 502.

  The decoded image generation unit 502 generates a decoded image using the index decoded by the decoding processing unit 500, the position of the symbol, and the symbol dictionary. More specifically, the decoded image generation unit 502 selects a corresponding symbol from the symbol dictionary based on the index, arranges the selected symbol in the decoded image based on the decoded position information, A decoded image is generated.

[Decryption operation]
FIG. 12 is a flowchart showing the decryption process (S20) by the decryption program 5.
As shown in FIG. 12, in step 200 (S200), the decoding processing unit 500 (FIG. 11) decodes input code data (FIG. 9) by text region encoding, and an index for identifying symbols. , Corresponding position information is acquired.
In step 202 (S202), the decoded image generation unit 502 selects a corresponding symbol from the symbol dictionary based on the index, and arranges the selected symbol in the decoded image based on the decoded position information. Then, a decoded image is generated and output.

As described above, the image processing apparatus 2 according to the present embodiment encodes an input image including a binary halftone dot pattern by text region encoding, and thus avoids deterioration in image quality due to halftone region encoding. be able to.
Further, since the image processing apparatus 2 in the present embodiment extracts symbols from the input image based on the period, phase, shape, and size of the binary halftone dot pattern, the halftone dot pattern in which the black pixels of the halftone dot pattern are adjacent to each other. Even in the case of continuous with the black pixels, it is possible to appropriately extract symbols and encode them at a high compression rate.

[Second Embodiment]
An image processing apparatus 2 according to the second embodiment of the present invention will be described.
FIG. 13 is a diagram illustrating a functional configuration of the second encoding program 6 that realizes the encoding method according to the present invention.
As illustrated in FIG. 13, the encoding program 6 includes a raster generation unit 400, a halftone dot feature extraction unit 600, a symbol dictionary creation unit 402, a symbol position generation unit 404, and an encoding unit 406. The encoding program 6 is such that the halftone dot feature extraction unit 600 performs screen processing to extract at least one of the period, phase, shape, and size of the binary halftone dot pattern (see FIG. 6). ) Is different.
Of the components shown in FIG. 13, components that are substantially the same as those shown in FIG. 6 are denoted by the same reference numerals.

In the encoding program 6, the raster generation unit 400 receives input image data in PDL format, converts the input image included in the input image data into raster data (color component image) of each color component, and extracts halftone dot features. Output to unit 600, symbol dictionary creation unit 402, and symbol position generation unit 404.
A halftone dot feature extraction unit 600 performs screen processing on the color component image input from the raster generation unit 400, and displays the dot pattern features (period, phase, shape, and size) obtained by the screen processing as symbols. Output to the dictionary creation unit 402.

14A and 14B are diagrams for explaining the screen processing in the encoding program 6. FIG. 14A shows the shape of the screen unit area and threshold parameters, and FIG. 14B shows the screen unit area and the phase. FIG. 14C and FIG. 14D illustrate a halftone dot pattern subjected to screen processing.
As shown in FIG. 14A, the feature of the halftone dot pattern is extracted by the halftone dot feature extraction unit 600 by comparing the threshold parameter (threshold matrix) with the pixel value of the input image. . The screen unit area is an area where each halftone dot pattern can be arranged, and has a size and shape of 5 × 5 pixels, for example. The threshold parameter of this example corresponds to a halftone dot pattern.
Further, as shown in FIG. 14B, the screen unit area is specified by the phase in the main scanning direction, for example. Further, the screen unit area can be compared with the pixel value of the input image at a predetermined cycle.

  The halftone dot feature extraction unit 600 performs screen processing on the input image, identifies halftone dot data, and extracts the period, phase, shape, and size of the halftone dot data. As illustrated in FIG. 14C, when the area in the input image has a medium density, the black pixel in the screen unit area does not continue to the black pixel in the adjacent unit area. On the other hand, as illustrated in FIG. 14D, when the area in the input image has a high density, the black pixels are continuous with the black pixels in the adjacent unit areas. Also in this case, the features of the halftone dot pattern are extracted by screen processing. In this way, the halftone dot feature extraction unit 600 extracts halftone dot pattern features from the input image.

FIG. 15 is a flowchart showing the encoding process (S30) by the encoding program 6.
As shown in FIG. 15, in step 300 (S300), when the PDL file is input as an input image, the raster generation unit 400 converts the PDL file into a color component image, and converts the halftone dot feature extraction unit 600, symbol dictionary creation unit. 402 and the symbol position generation unit 404. The halftone dot feature extraction unit 600 performs screen processing on the input color component image to extract the period, phase, shape, and size of the halftone dot pattern, and outputs the extracted result to the symbol dictionary creation unit 402.

In step 102 (S102), the symbol dictionary creation unit 402 creates a symbol dictionary based on the extracted halftone dot pattern period, phase, shape, and size.
In step 104 (S104), the symbol position generation unit 404 generates symbol / position correspondence data using the created symbol dictionary.
In step 106 (S106), the encoding unit 406 encodes the symbol / position correspondence data by text region encoding to generate code data.

  As described above, the image processing apparatus 2 in the present embodiment extracts the period, phase, shape, and size of the binary halftone dot pattern from the input image and creates a symbol dictionary using these parameters. Even when the above parameter is not included in the input image data, symbols can be appropriately extracted and encoded at a high compression rate.

FIG. 1A illustrates a halftone area encoding process. FIG. 1A illustrates a binary image to be encoded, and FIG. 1B is created in the halftone area encoding process. An image dictionary is illustrated, and FIG. 1C illustrates code data generated using the image dictionary and a decoded image thereof. It is a figure which illustrates the image dictionary and decoded image at the time of encoding the binary input image in which an edge exists by a halftone area | region encoding process. FIGS. 3A and 3B illustrate a text area encoding process. FIG. 3A illustrates a case where the input image has a low density, and FIG. 3B illustrates a case where the input image has a high density. It is a figure which illustrates the encoding process by the image processing apparatus 2 which concerns on this invention. It is a figure which illustrates the hardware constitutions of the image processing apparatus 2 to which the encoding method and decoding method which concern on this invention are applied centering on the control apparatus 20. FIG. It is a figure which illustrates the functional structure of the 1st encoding program 4 which is performed by the control apparatus 20 (FIG. 5), and implement | achieves the encoding method which concerns on this invention. It is a figure explaining the characteristic of the binary dot pattern used in preparation of a symbol dictionary. FIGS. 8A and 8B illustrate a binary halftone dot pattern encoding process. FIG. 8A illustrates a high-density input image, and FIG. 8B illustrates a symbol dictionary created from the input image. FIG. 8C illustrates symbol / position correspondence data generated from the input image. It is a figure which illustrates the code data produced | generated by the encoding program 4 (FIG. 6). It is a flowchart which shows the encoding process (S10) by the encoding program 4. It is a figure which illustrates the functional structure of the decoding program 5 which is performed by the control apparatus 20 (FIG. 5) and implement | achieves the decoding method which concerns on this invention. It is a flowchart which shows the decoding process (S20) by the decoding program 5. FIG. FIG. 3 is a diagram illustrating a functional configuration of a second encoding program 6 that realizes an encoding method according to the present invention. 14A and 14B are diagrams for explaining screen processing in the encoding program 6. FIG. 14A shows the shape of the screen unit area and threshold parameters, and FIG. 14B shows the relationship between the screen unit area and the phase. FIGS. 14C and 14D illustrate binary halftone dot patterns that have undergone screen processing. It is a flowchart which shows the encoding process (S30) by the encoding program 6. FIG.

Explanation of symbols

2 ... Image processing device 10 ... Printer device 20 ... Control device 202 ... CPU
204 ... Memory 22 ... Communication device 24 ... Recording device 4 ... Coding program 400 ... Raster generator 402 ... Symbol dictionary generator 404 ... Symbol position generator 406 ... Encoding unit 5: decoding program 500 ... decoding processing unit 502 ... decoded image generation unit 6 ... encoding program 600 ... halftone dot feature extraction unit

Claims (13)

Input means for inputting an input image including a binary halftone dot pattern and features of the binary halftone dot pattern;
Halftone dot feature extracting means for performing screen processing on the input image input by the input means and extracting features of a binary halftone dot pattern;
A dictionary creating means for creating a dictionary for identifying a binary halftone dot pattern based on the features of the binary halftone dot pattern extracted by the halftone dot feature extracting means ;
An image coding apparatus comprising: coding means for coding an input image based on the dictionary created by the dictionary creating means. The encoding means encodes an input image based on the text area encoding defined in JBIG2 based on the dictionary created by the dictionary creating means.
  The image encoding device according to claim 1. The image coding apparatus according to claim 1, wherein the input unit inputs an input image including at least one of a period, a phase, a shape, and a size of the binary halftone dot pattern as a characteristic of the binary halftone dot pattern. The image encoding device according to claim 1, wherein the encoding means encodes identification information for identifying a binary halftone dot pattern and a position at which the binary halftone dot pattern appears in an input image in association with each other. . Extracting means for performing screen processing on an input image including a binary halftone dot pattern and extracting features of the binary halftone dot pattern;
A dictionary creating means for creating a dictionary for identifying a binary halftone dot pattern based on the characteristics of the binary halftone dot pattern extracted by the extracting means;
An image coding apparatus comprising: coding means for coding an input image based on the dictionary created by the dictionary creating means. The image encoding device according to claim 5 , wherein the extraction unit extracts at least one of a period, a phase, a shape, and a size of a binary halftone dot pattern. The image encoding device according to claim 5 , wherein the encoding means encodes identification information for identifying a binary halftone dot pattern and a position at which the binary halftone dot pattern appears in an input image in association with each other. . An input image including a binary halftone dot pattern and a feature of the binary halftone dot pattern is input, and based on the feature of the binary halftone dot pattern extracted by performing screen processing on the input image , a binary halftone dot is obtained. A decoding unit for creating a dictionary for identifying a pattern and decoding the code data based on code data generated by encoding an input image based on the dictionary;
An image decoding apparatus comprising: an image generation unit configured to generate a decoded image using a decoding result obtained by the decoding unit and a dictionary. The image decoding apparatus according to claim 8 , wherein the decoding unit decodes the identification information of the binary halftone dot pattern and the position where the binary halftone dot pattern appears in the input image. The image generating means generates a decoded image by further using the binary halftone dot pattern identification information decoded by the decoding means and the position where the binary halftone dot pattern appears in the input image. 10. The image decoding device according to 9 . In an image encoding device including a computer,
An input step for inputting an input image including a binary halftone dot pattern and features of the binary halftone dot pattern;
A halftone dot feature extracting step of performing screen processing on the input image and extracting a characteristic of a binary halftone dot pattern;
Creating a dictionary for identifying a binary halftone dot pattern based on the extracted binary halftone dot pattern characteristics;
A program for causing a computer of the image encoding device to execute an encoding step of encoding an input image based on the created dictionary. In an image encoding device including a computer,
An extraction step of performing screen processing on an input image including a binary halftone dot pattern and extracting features of the binary halftone dot pattern;
Creating a dictionary for identifying a binary halftone dot pattern based on the extracted binary halftone dot pattern characteristics;
A program for causing a computer of the image encoding device to execute an encoding step of encoding an input image based on the created dictionary. In an image decoding apparatus including a computer,
An input image including a binary halftone dot pattern and a feature of the binary halftone dot pattern is input, and based on the feature of the binary halftone dot pattern extracted by performing screen processing on the input image , a binary halftone dot is obtained. A decoding step of creating a dictionary for identifying a pattern and decoding the code data based on code data generated by encoding an input image based on the dictionary;
A program for causing a computer of the image decoding apparatus to execute an image generation step of generating a decoded image using the decoded result and a dictionary.

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