JP2007060334A - Image processing device and method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize unification of data management and improve processing efficiency in a process of partial image data rewrite. <P>SOLUTION: Code data in a replacing objective portion are separated with a restart marker in original code data, and are replaced with a rewriting code data compressed under the same condition as the original code data. In addition, the replacement position information and code data in the replacement objective portion are stored in an application marker. As a result, the replacement of the original code data is realized. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image processing apparatus and an image processing method, and more particularly to a partial image rewriting technique for rewriting a part of an image.

  As one of highly efficient compression / decompression methods for natural images, JPEG which is an international standard is known. In this JPEG system, an 8 × 8 pixel block called MCU (Minimum Coded Unit) is one unit. The MCU is compressed as follows.

  First, two-dimensional DCT transformation is performed on one MCU. Quantization is performed on 64 pieces of data converted into DCT coefficients. FIG. 11 is a diagram illustrating an example of the quantization step. Since human eyes have a feature that high frequency components are not conspicuous, as shown in FIG. 11, the omission of low frequency components is reduced and the omission of high frequency components is increased.

  FIG. 12 is a diagram illustrating an example of quantized DCT coefficients. In FIG. 12, in particular, one coefficient at the upper left is called a DC component, and the remaining 63 coefficients are called AC components.

  Compressed data can be obtained by entropy encoding the 64 coefficients quantized in this way and expressing them by a Huffman code.

  FIG. 13 shows a zigzag scan order. At the time of encoding, data processing is performed in the zigzag order as shown in FIG. Specifically, first, since the first DC component has a strong correlation with the DC component of the adjacent MCU, a difference value from the DC coefficient of the immediately preceding MCU is obtained, and variable length coding processing is performed.

  The remaining 63 AC components are run-length encoded. In this method, the number of zeros is counted until a non-zero coefficient appears, and at the same time, the count number of zero and the non-zero coefficient are output together. To do.

  FIG. 14 is a diagram illustrating an example of run-length encoding. When data is read in zigzag order as shown in FIG. 13, 3 appears after 2 0s. In this case, 2/3 (number of 0 / non-zero coefficient value) is the run-length code.

  Then, 20 0s continue, and then 10 appears. Thus, when 16 or more consecutive 0s continue, the first 16 are ZRL codes, the codes are represented by F / 0, and the remaining 4 0s and 10 are codes represented by 4/10. Is output.

  Next, all the remaining 39 coefficients are 0, and this case is particularly called EOB, and the code is 0/0.

  Run-length encoding is performed as described above, and the number of zeros is represented by 4 bits because the maximum number of zeros is 15. Then, the run-length encoded run / coefficient coefficients are grouped.

  FIG. 15 is a diagram illustrating a group number corresponding to a quantization coefficient. As shown in FIG. 15, in the case of JPEG, the coefficient is 11 bits, and this 11-bit coefficient is assigned to a 4-bit group number. Variable length coding processing is performed on the data that has been run-length coded as described above.

  FIG. 16 is a diagram illustrating an example of a code table. From this code table, a total of 8 bits of run / group number including the number of 0 4 bits and the group number 4 bits and the occurrence frequency are acquired. A variable length code is obtained from the occurrence frequency and the initial value of the variable length encoding process. As an initial value, the Min code that is the minimum code of each code length and the occurrence frequency of the Min code are stored.

  FIG. 17 is a diagram illustrating an example of initial values used for Huffman encoding / decoding. The number of codes for each code length is required to create the initial value, but the initial value may be created and input externally, or the number of codes for each code length may be created internally from the code table. I do not care.

  On the other hand, when the code data is decompressed, the original image can be restored by performing inverse quantization and inverse DCT transform after extracting data in MCU units by Huffman decoding as a procedure reverse to the above-described compression. it can.

  FIG. 18 is a diagram showing an outline of the JPEG format. As shown in FIG. 18, the entire JPEG format is composed of a collection of data called segments, which are delimited by 2-byte symbols called markers.

  As described above, the JPEG format can include various types of information such as the Huffman table and the image size in addition to the code data by using the marker.

  Here, there is a restart marker as a JPEG marker. Normally, since the DC component uses a difference value from the DC component of the immediately preceding MCU, it cannot be decoded without the information of the immediately preceding MCU. However, by inserting a restart marker, the DC component of the immediately preceding MCU It is not necessary to take the difference value.

  That is, the block delimited by the restart marker has no correlation with the adjacent block, and can be configured by only that block. The restart marker is inserted in units of several MCUs, and the insertion unit is stored in the code data as a restart interval definition segment.

  In addition, there is an application segment as a JPEG marker, and numbers 0 to 15 can be added. In a normal decoding sequence, this segment is ignored, but information necessary for the upper application can be stored. For example, in a JPEG file compliant with the Exif standard, Exif information is stored in the first application marker.

Note that more detailed specifications for JPEG are disclosed in known standardization recommendation documents shown in Patent Document 1, Patent Document 2, and Non-Patent Document 1.
JP 2002-84493 A JP 2003-189109 A ISO / IEC standard 10918

  Here, when partial rewriting is performed on an image encoded by the above-described JPEG method, there are a procedure for expanding code data, a procedure for rewriting an image, and a procedure for encoding a rewritten image. Necessary.

  However, since the JPEG method is usually processed in units of one image, the time required for processing increases as the image size increases, and the amount of buffer memory required also increases. For example, in the case of a 4: 2: 2 image of 2560 × 1920 pixels, a capacity of approximately 9 Mbytes is required.

  JPEG is an irreversible compression method, and if rewriting is repeated, compression processing occurs each time, and it is expected that image quality deterioration of the original image will become severe.

  Since the original image cannot be restored after rewriting, it is necessary to manage the original image data separately from the rewritten data when it is necessary to leave the original image data.

  The present invention has been made in view of this point, and an object of the present invention is to improve the processing efficiency and to centralize data management in the partial image rewriting process.

That is, the present invention is an image processing apparatus for replacing a part of encoded original image data with rewrite image data,
Header information is read from the code data of the original image data, and at least a Huffman table and a header reading unit for acquiring information indicating a restart marker insertion interval;
An encoding unit that encodes the image data for rewriting using a Huffman table acquired by the header reading unit;
The encoded data of the portion to be replaced specified by the Nth (N is a natural number) restart marker from the Mth (M is a natural number) restart marker in the code data of the original image data is encoded. And a code replacement unit that replaces the code data of the rewritten image data encoded by the unit.

Further, the present invention is an image processing method for replacing a part of encoded original image data with image data for rewriting,
A procedure for reading header information from the code data of the original image data, and obtaining information indicating at least a Huffman table and a restart marker insertion interval;
A procedure for encoding the rewriting image data using the acquired Huffman table;
The encoded data of the portion to be replaced specified by the Nth (N is a natural number) restart marker from the Mth (M is a natural number) restart marker in the code data of the original image data is encoded. And a procedure for replacing the rewritten image data with the code data.

  As described above, according to the present invention, in the partial image rewriting process, it is not necessary to once decompress the original image data, so that the processing efficiency is improved and the image can be rewritten with a buffer memory having a required size. Is possible. Even when irreversible encoding is used, unnecessary image quality degradation can be suppressed.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The following description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or its application.

<Embodiment 1>
FIG. 1 is a block diagram showing a configuration of an image processing apparatus according to Embodiment 1 of the present invention. In FIG. 1, reference numeral 11 denotes a code input unit that outputs code data of an original image to the header reading unit 13 and also to the code replacement unit 15.

  The header reading unit 13 reads information on the Huffman table and restart marker insertion interval from the input code data, and outputs the information to the encoding unit 14.

  The encoding unit 14 receives the rewritten image data from the image input unit 12, encodes the rewritten image data using the input Huffman table, and outputs the encoded image data to the code replacement unit 15.

  The code replacement unit 15 replaces all the codes from the designated start position to the end position in the code data of the original image input from the code input unit 11 with the code data of the rewritten image.

  FIG. 5 is a flowchart showing the processing procedure of the partial image rewriting method using the image processing apparatus according to the first embodiment. As shown in FIG. 5, first, in step S101, code data of the original image is input from the code input unit 11, and the process proceeds to subsequent step S102.

  In step S102, the header reading unit 13 reads the information of the Huffman table and the restart marker insertion interval from the input code data, and proceeds to subsequent step S103.

  In step S103, the rewritten image data is input from the image input unit 12, and the process proceeds to the subsequent step S104.

  In step S104, the encoding unit 14 encodes the input rewritten image data using the Huffman table read in step S102, and proceeds to subsequent step S105.

  In step S105, as shown in FIG. 9, from the code data of the original image, a rewrite start position (Mth (M is a natural number) restart marker) and end position (Nth (N is a natural number)). The restart marker) is designated in units of restart intervals, and the process proceeds to the subsequent step S106.

  In step S106, as shown in FIG. 9, the code replacement unit 15 replaces all the codes from the start position to the end position specified in step S105 with the code data of the rewritten image encoded in step S104. Proceed to step S107.

  In step S107, as shown in FIG. 10, the code replacement unit 15 stores the rewrite position information specified in step S105 and the code data of the portion to be replaced in step S106 in the application marker, and ends the process. To do.

  As described above, according to the image processing apparatus according to the first embodiment, processing for blocks that are not rewritten does not occur, so that the processing time can be shortened and the amount of buffer memory necessary for processing can be reduced.

  In addition, since recompression processing does not occur, image quality deterioration does not occur for blocks that are not rewritten.

  Furthermore, since it is possible to have the information of the original image data together, it becomes possible to centrally manage the original image data and the rewritten image data, and by reading out the original image data information and performing replacement in the same manner, It is possible to restore the rewritten image to the original image.

  FIG. 8 is a flowchart showing a processing procedure of a partial image rewriting method for restoring code data after rewriting to original image data.

  As shown in FIG. 8, first, in step S401, the replaced code data is input from the code input unit 11, and the process proceeds to the subsequent step S402.

  In step S402, the header reading unit 13 reads the code data and replacement position information of the original image from the application segment of the replaced code data, and proceeds to subsequent step S403.

  In step S403, based on the information read in step S402, the rewrite start position (Mth restart marker) and end position (Nth restart marker) are rewritten from the replaced code data. The start marker insertion unit is designated, and the process proceeds to the subsequent step S404.

  In step S404, the code replacement unit 15 replaces all the codes from the start position to the end position specified in step S105 with the original code data read in step S402 (see FIG. 9), and ends the process. As a result, the original code data can be restored.

  In the image processing apparatus according to the first embodiment, the N-th restart marker has been described as the (M + 1) -th restart marker (see FIG. 9). It is sufficient that the restart marker is the first and subsequent (M <N) restart markers.

  Furthermore, although the case where position information and code data are stored in the same application marker has been described (see FIG. 10), each may be stored as separate segments. Moreover, although the case where the position data and the code data of the part to be replaced are stored in the application marker has been described, the present invention is not limited to this form, and may be stored in another segment such as a comment marker, for example. In addition, storage may be omitted in order to reduce the data size.

  In addition, although it has been described that a separate image is prepared for input of a replacement image, the original code data is expanded in units of restart intervals including the portion to be rewritten, and the rewritten image is then rewritten. You may make it input.

  In addition, the rewritten image is configured to input an uncompressed image. For example, using the image processing apparatus illustrated in FIG. 4, a configuration in which existing JPEG code data compressed using the same Huffman table as the original code data is input. It may be.

  Specifically, the image processing apparatus in FIG. 4 is a decoding-dedicated apparatus including the code input unit 11, the header reading unit 13, and the code rewriting unit 15, but has a configuration that does not include the encoding unit. Even if it exists, it becomes possible to perform partial rewriting of image data.

<Embodiment 2>
FIG. 2 is a block diagram showing the configuration of the image processing apparatus according to the second embodiment of the present invention. The difference from the first embodiment is that it further includes a scramble processing unit 21 that scrambles the information of the original image data. Therefore, the same parts as those of the first embodiment are denoted by the same reference numerals and the differences are described below. Only explained.

  As shown in FIG. 2, the scramble processing unit 21 performs scramble processing on code data of a part to be replaced in original image data.

  FIG. 6 is a flowchart showing the processing procedure of the partial image rewriting method using the image processing apparatus according to the second embodiment. Note that the same processing elements as those in the partial image rewriting method of the first embodiment are denoted by the same step numbers, and description thereof is omitted.

  As shown in FIG. 6, after step S101 to step S106 are executed, the process proceeds to subsequent step S201. In step S201, the scramble processing unit 21 scrambles the rewrite position information specified in step S105 and the code data of the portion to be replaced in step S106, and the process proceeds to the subsequent step S202.

  In step S202, the code replacement unit 15 uses the scramble release key performed in step S201 as an application marker in addition to the rewrite position information specified in step S105 or the code data of the part to be replaced in step S106. Store it and finish the process.

  As described above, according to the second embodiment, since the information of the original image data is scrambled, the unintended restoration of the original image by the third party can be suppressed.

  In the second embodiment, the descrambling key is stored in the application marker. However, the present invention is not limited to this mode. For example, the descrambling key may be stored in another segment such as a comment marker. In order to reduce the size, storage may not be performed.

<Embodiment 3>
FIG. 3 is a block diagram showing the configuration of the image processing apparatus according to the third embodiment of the present invention. The difference from the first embodiment is that it further includes a watermark insertion unit 31 that inserts an identification ID into the code data as a watermark (digital watermark). Only the differences will be described with the same reference numerals.

  As shown in FIG. 3, the watermark insertion unit 31 inserts a watermark into code data of a portion to be replaced in original image data.

  FIG. 7 is a flowchart showing the processing procedure of the partial image rewriting method using the image processing apparatus according to the third embodiment. The same processing elements as those in the partial image rewriting method of the first embodiment are denoted by the same step numbers, and description thereof is omitted.

  As shown in FIG. 7, after step S101 to step S106 are executed, the process proceeds to subsequent step S301. In step S301, the watermark insertion unit 31 inserts a watermark into the code data of the portion to be replaced in step S106, and the process proceeds to subsequent step S107.

  In step S302, the code replacement unit 15 stores the rewrite position information specified in step S105 and the code data of the part to be replaced in step S106 in the application marker, and ends the process.

  As described above, according to the third embodiment, by inserting an identification ID as a watermark, for example, when an illegal outflow of image data occurs, the identification ID is identified and the outflow source is specified. Advantageous effects can be obtained.

  As described above, the present invention is extremely useful and industrially utilized because it provides a highly practical effect of improving the processing efficiency and centralizing data management in the partial image rewriting process. The possibility is high.

1 is a block diagram illustrating a configuration of an image processing apparatus according to a first embodiment of the present invention. It is a block diagram which shows the structure of the image processing apparatus which concerns on this Embodiment 2. It is a block diagram which shows the structure of the image processing apparatus which concerns on this Embodiment 3. It is a block diagram which shows another structure of the image processing apparatus for decompress | restoring the code data after rewriting in this Embodiment 1 to original image data. It is a flowchart figure which shows the process sequence of the partial image rewriting method using the image processing apparatus which concerns on this Embodiment 1. FIG. It is a flowchart figure which shows the process sequence of the partial image rewriting method in this Embodiment 2. It is a flowchart figure which shows the process sequence of the partial image rewriting method in this Embodiment 3. It is a flowchart figure which shows the process sequence of the partial image rewriting method for decompress | restoring the code data after rewriting in this Embodiment 1 to original image data. FIG. 3 is a conceptual diagram illustrating replacement of original image code data and rewritten code data in the first embodiment. It is a conceptual diagram which shows the state which memorize | stores the positional information and code | cord | chord data of rewriting in this Embodiment 1 in an application marker. It is a figure which shows an example of a quantization step. It is a figure which shows an example of the quantized DCT coefficient. It is a figure which shows a zigzag scan order. It is a figure which shows an example of run length encoding. It is a figure which shows the group number corresponding to a quantization coefficient. It is a figure which shows an example of a code table. It is a figure which shows an example of the initial value used for Huffman encoding / decoding. It is a figure which shows the outline | summary of a JPEG format.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Code input part 12 Image input part 13 Header reading part 14 Encoding part 15 Code replacement part 21 Scramble process part 31 Watermark insertion part

Claims (10)

An image processing apparatus for replacing a part of encoded original image data with rewriting image data,
Header information is read from the code data of the original image data, and at least a Huffman table and a header reading unit for acquiring information indicating a restart marker insertion interval;
An encoding unit that encodes the image data for rewriting using a Huffman table acquired by the header reading unit;
The encoded data of the portion to be replaced specified by the Nth (N is a natural number) restart marker from the Mth (M is a natural number) restart marker in the code data of the original image data is encoded. An image processing apparatus comprising: a code replacement unit that replaces the code data of the rewritten image data encoded by the unit. The image processing apparatus according to claim 1,
The image processing apparatus, wherein the code replacement unit is configured to include, in the code data, replacement position information in the code data of the original image data and code data of a portion to be replaced as a segment. The image processing apparatus according to claim 2,
An image processing apparatus, further comprising: a scramble processing unit that scrambles the replacement position information in the code data of the original image data and the code data of a part to be replaced. The image processing apparatus according to claim 3,
The image processing device, wherein the code replacement unit is configured to include the scramble key information as a segment in code data. The image processing apparatus according to claim 1,
An image processing apparatus, further comprising a watermark insertion unit that inserts a watermark into code data of a portion to be replaced in the original image data. An image processing method for replacing a part of encoded original image data with image data for rewriting,
A procedure for reading header information from the code data of the original image data, and obtaining information indicating at least a Huffman table and a restart marker insertion interval;
A procedure for encoding the rewriting image data using the acquired Huffman table;
The encoded data of the portion to be replaced specified by the Nth (N is a natural number) restart marker from the Mth (M is a natural number) restart marker in the code data of the original image data is encoded. And a procedure for replacing the rewritten image data with code data. The image processing method according to claim 6.
An image processing method, further comprising a step of including the replacement position information in the code data of the original image data and the code data of the part to be replaced as a segment in the code data. The image processing method according to claim 7,
An image processing method, further comprising a step of scrambling the replacement position information in the code data of the original image data and the code data of a part to be replaced. The image processing method according to claim 8, wherein
An image processing method, further comprising a step of including the scramble key information in the code data as a segment. The image processing method according to claim 6.
An image processing method, further comprising a step of inserting a watermark into code data of a portion to be replaced in the original image data.