JP2004234565A - Displacement correction device, image processor, program, storage medium, and displacement correction method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a displacement correction device capable of correcting a displacement of an image reference point of the present page to a reference page without going through a complicated processing of decoding and inversely quantizing code string data. <P>SOLUTION: The displacement amount of the image reference point of the present page to the reference page is detected on the basis of the analysis result of the syntax of code string data formed by frequency-converting and hierarchically compression-encoding a pixel value of every rectangular section of a predetermined area of static image data divided to a plurality of sections (step S5), and the image reference point of page coordinates of the present page is moved so as to match with the image reference point of page coordinates of the reference page according to the displacement amount (step S8). Accordingly, the displacement of the image reference point of the present page to the reference page can be corrected without going through the complicated processing of decoding and inversely quantizing the code string data. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a displacement correction device, an image processing device, a program, a storage medium, and a displacement correction method.
[0002]
[Prior art]
2. Description of the Related Art Due to advances in image input technology and output technology thereof, demands for higher definition of images have been extremely increased in recent years. For example, taking a digital camera (Digital Camera) as an example of an image input device, the price of a high-performance charge coupled device (CCD: Charge Coupled Device) having more than 3 million pixels has been reduced, and the price range has become widespread. Products have come to be widely used. It is said that this increasing tendency of the number of pixels will continue for a while.
[0003]
On the other hand, with regard to image output / display devices, for example, products in the hard copy field such as laser printers, ink jet printers and sublimation printers, and flat devices such as CRTs, LCDs (liquid crystal display devices), and PDPs (plasma display devices). The high definition and low price of products in the field of soft copy of panel displays are remarkable.
[0004]
Due to the effect of bringing high-performance, low-cost image input / output products to the market, the popularization of high-definition images has begun, and it is expected that demand for high-definition images will increase in all scenes in the future. Indeed, the development of technologies related to networks, such as personal computers and the Internet, is accelerating these trends. In particular, recently, mobile devices such as mobile phones and notebook personal computers have become very popular, and opportunities to transmit or receive high-definition images from any point using communication means have been rapidly increasing.
[0005]
Against this background, the demand for higher performance or multifunctional image compression / decompression technology that facilitates the handling of high-definition images will inevitably increase in the future.
[0006]
Therefore, in recent years, a new method called JPEG2000, which can restore a high-quality image even at a high compression ratio, is being standardized as one of the image compression methods satisfying such demands. In JPEG2000, by dividing an image into rectangular areas (tiles), it is possible to perform compression / expansion processing in a small memory environment. That is, each tile is a basic unit when executing the compression / decompression process, and the compression / decompression operation can be performed independently for each tile.
[0007]
By the way, generally, when a paper document (original document) is digitized and stored, the following processes are sequentially executed. First, paper documents (original documents) are read one by one using an image input device such as a scanner or a digital still camera. Next, the read image data is converted into encoded data such as JPEG or JPEG2000 using an image compression device. Finally, the compressed encoded data is stored in a storage device.
[0008]
However, when reading a plurality of paper documents (documents) using an image input device such as a scanner, the origin position of the page coordinates of the digitized paper documents (documents) differs for each paper document (document). Sometimes. Here, the page coordinates are coordinates provided on the digitized paper document (document), and as shown in FIG. 21, the origin position of the page coordinates is the origin position of the digitized paper document (document). One corner in the document range. That is, the fact that the origin position of the page coordinates of the digitized paper document (document) differs for each paper document (document) means that the reading range provided in an image input device such as a scanner as shown in FIG. This means that the relative positional relationship with respect to the absolute coordinates (read coordinates) differs for each paper document (original).
[0009]
If the origin position of the page coordinates of the digitized paper document (original) is different for each paper document (original), an image search process is performed on those paper documents (original). In addition, a highly accurate search result cannot be obtained.
[0010]
Therefore, in order to correct such a positional deviation of the page coordinates, the position of the paper document (original document) is adjusted again.
[0011]
[Problems to be solved by the invention]
However, it is practically impossible to perform registration for each input paper document (original document) when a large number of paper documents (original documents) are to be input.
[0012]
Also, a method of correcting a position shift of page coordinates based on coded data such as JPEG or JPEG2000 converted using an image compression device is being studied. However, a method of decoding a coded frequency conversion coefficient value is proposed. Further, since complicated processing such as inverse quantization is required, there is a problem that the processing time is long and the processing speed is low.
[0013]
An object of the present invention is to provide a position shift correction apparatus and an image processing apparatus capable of correcting a position shift of an image reference point of a current page with respect to a reference page without going through a complicated process of decoding and dequantizing code string data. , A program, a storage medium, and a position shift correction method.
[0014]
[Means for Solving the Problems]
The position shift correcting apparatus according to the first aspect of the present invention is created by dividing a predetermined area of the still image data into one or a plurality of rectangular areas, frequency-converting pixel values for each of the rectangular areas, and hierarchically compressing and encoding. Syntactic analysis means for analyzing the syntax of the encoded code string data, and displacement amount detection means for detecting the displacement amount of the image reference point of the current page with respect to the reference page to be compared based on the analysis result of the syntax analysis means And a page coordinate moving means for moving the image reference point of the page coordinates of the current page so as to match the image reference point of the page coordinates of the reference page in accordance with the amount of displacement detected by the displacement amount detecting means. , Is provided.
[0015]
Therefore, the predetermined page of the still image data is subjected to the frequency conversion of the pixel value for each rectangular area and hierarchically compression-encoded, and the current page relative to the reference page detected based on the analysis result of the syntax of the code string data created. The image reference point at the page coordinates of the current page is moved according to the displacement amount of the image reference point so as to match the image reference point at the page coordinates of the reference page. This makes it possible to correct the displacement of the image reference point of the current page with respect to the reference page without going through a complicated process of decoding and dequantizing the code string data.
[0016]
According to a second aspect of the present invention, there is provided the positional deviation correcting device according to the first aspect, further comprising condition specifying means for specifying syntax analysis conditions in the syntax analysis means.
[0017]
Therefore, for example, by arbitrarily specifying the area of the rectangular region, the number of components (color components), the band of the subband, and the like as the parsing conditions, the accuracy of the displacement amount and the detection processing speed can be adjusted according to the user's desire. It becomes possible to optimize.
[0018]
According to a third aspect of the present invention, in the position shift correcting apparatus according to the first or second aspect, the position shift amount detecting means determines a packet length of a packet constituting code string data based on an analysis result of the syntax analyzing means. Packet length reading means to be read, packet length storage means for storing one packet length read by the packet length reading means as the packet length of a reference page to be compared, and packet length reading means to be read by the packet length reading means. And a difference detecting means for detecting a difference value between the packet length of the current page and the packet length of the reference page as a positional shift amount of an image reference point with respect to the reference page of the current page.
[0019]
Therefore, the amount of displacement of the image reference point of the current page with respect to the reference page is detected by comparing the packet length, which is the code amount of the frequency conversion coefficient value between the current page and the reference page for a predetermined area of the still image data. You. This eliminates the need for a complicated process of decoding the coded frequency transform coefficient value and further performing inverse quantization upon detecting the amount of displacement of the image reference point of the current page with respect to the reference page. It is possible to quickly and accurately determine the amount of displacement of the image reference point of the current page.
[0020]
According to a fourth aspect of the present invention, in the position shift correcting device according to any one of the first to third aspects, the rectangular area as a division unit is a tile.
[0021]
Therefore, a discrete wavelet transform can be used as the frequency transform.
[0022]
According to a fifth aspect of the present invention, in the position shift correcting apparatus according to any one of the first to third aspects, the rectangular area as a division unit is a precinct.
[0023]
Therefore, even when the tile division is not performed (all image areas = tiles), it is possible to speed up the detection of the amount of displacement of the image reference point of the current page with respect to the reference page, as in the case of the tile unit. Further, it becomes possible to set the detection unit to an image area smaller than the tile.
[0024]
According to a sixth aspect of the present invention, in the position shift correcting device according to any one of the first to third aspects, the rectangular area as a division unit is a code block.
[0025]
Therefore, even when the tile division is not performed (all image areas = tiles), it is possible to speed up the detection of the amount of displacement of the image reference point of the current page with respect to the reference page, as in the case of the tile unit. Further, it becomes possible to set the detection unit to an image area smaller than the tile.
[0026]
According to a seventh aspect of the present invention, in the position shift correcting apparatus according to any one of the first to sixth aspects, when the position shift amount of the image reference point of the current page with respect to the reference page exceeds a predetermined value, the page shift is performed. The position shift is not corrected by moving the page coordinates by the coordinate moving means.
[0027]
Therefore, for example, by setting the predetermined value to a value that indicates that the document is out of the reading range, the positional deviation correction is executed until the positional deviation can not be corrected by moving the page coordinates. Can be avoided.
[0028]
An image processing apparatus according to the present invention is an image compression apparatus that divides still image data into one or a plurality of rectangular areas, frequency-converts pixel values for each of the rectangular areas, and hierarchically compresses and codes the image data. 8. The positional deviation according to claim 1, wherein the positional deviation of an image reference point of a current page with respect to a reference page is corrected based on code string data of a predetermined area of the still image data compression-encoded by the compression device. A correction device.
[0029]
Therefore, it is possible to provide an image processing apparatus that performs the same operation as the invention according to any one of claims 1 to 7 when compressing an image.
[0030]
The program according to the ninth aspect of the present invention is a program that is installed on a computer or interpreted and executed by the computer, wherein the predetermined area of the still image data is divided into one or a plurality of rectangular areas. A syntax analysis function that analyzes the syntax of code string data created by frequency-converting pixel values for each rectangular area and hierarchically compressing and encoding them, and a reference to be compared based on the analysis result of this syntax analysis function A position shift amount detection function for detecting the position shift amount of the image reference point of the current page with respect to the page, and referring to the image reference point of the page coordinates of the current page according to the position shift amount detected by the position shift amount detection function. And a page coordinate moving function for moving the page so as to match the image reference point of the page coordinates.
[0031]
Therefore, the predetermined page of the still image data is subjected to the frequency conversion of the pixel value for each rectangular area and hierarchically compression-encoded, and the current page relative to the reference page detected based on the analysis result of the syntax of the code string data created. The image reference point at the page coordinates of the current page is moved according to the displacement amount of the image reference point so as to match the image reference point at the page coordinates of the reference page. This makes it possible to correct the displacement of the image reference point of the current page with respect to the reference page without going through a complicated process of decoding and dequantizing the code string data.
[0032]
According to a tenth aspect of the present invention, in the program according to the ninth aspect, the computer causes the computer to execute a condition specifying function for specifying a syntax analysis condition in the syntax analysis function.
[0033]
Therefore, for example, by arbitrarily specifying the area of the rectangular region, the number of components (color components), the band of the subband, and the like as the parsing conditions, the accuracy of the displacement amount and the detection processing speed can be adjusted according to the user's desire. It becomes possible to optimize.
[0034]
According to an eleventh aspect of the present invention, in the program according to the ninth or tenth aspect, the position shift amount detection function reads a packet length of a packet constituting code string data based on an analysis result of the syntax analysis function. A reading function, a packet length storage function for storing the one packet length read by the packet length reading function as the packet length of a reference page to be compared, and a current page read by the packet length reading function And a difference detection function of detecting a difference value between the packet length of the reference page and the packet length of the reference page as a positional shift amount of an image reference point with respect to a reference page of a current page.
[0035]
Therefore, the amount of displacement of the image reference point of the current page with respect to the reference page is detected by comparing the packet length, which is the code amount of the frequency conversion coefficient value between the current page and the reference page for a predetermined area of the still image data. You. This eliminates the need for a complicated process of decoding the coded frequency transform coefficient value and further performing inverse quantization upon detecting the amount of displacement of the image reference point of the current page with respect to the reference page. It is possible to quickly and accurately determine the amount of displacement of the image reference point of the current page.
[0036]
According to a twelfth aspect of the present invention, in the program according to any one of the ninth to eleventh aspects, the rectangular area as a division unit is a tile.
[0037]
Therefore, a discrete wavelet transform can be used as the frequency transform.
[0038]
According to a thirteenth aspect of the present invention, in the program according to any one of the ninth to eleventh aspects, the rectangular area as a division unit is a precinct.
[0039]
Therefore, even when the tile division is not performed (all image areas = tiles), it is possible to speed up the detection of the amount of displacement of the image reference point of the current page with respect to the reference page, as in the case of the tile unit. Further, it becomes possible to set the detection unit to an image area smaller than the tile.
[0040]
According to a fourteenth aspect of the present invention, in the program according to any one of the ninth to eleventh aspects, the rectangular area that is a division unit is a code block.
[0041]
Therefore, even when the tile division is not performed (all image areas = tiles), it is possible to speed up the detection of the amount of displacement of the image reference point of the current page with respect to the reference page, as in the case of the tile unit. Further, it becomes possible to set the detection unit to an image area smaller than the tile.
[0042]
According to a fifteenth aspect of the present invention, in the program according to any one of the ninth to fourteenth aspects, when the positional shift amount of the image reference point of the current page with respect to the reference page exceeds a predetermined value, the page coordinate movement function is performed. The computer does not cause the computer to execute the displacement correction due to the movement of the page coordinates.
[0043]
Therefore, for example, by setting the predetermined value to a value that indicates that the document is out of the reading range, the positional deviation correction is executed until the positional deviation can not be corrected by moving the page coordinates. Can be avoided.
[0044]
A storage medium according to a sixteenth aspect stores the program according to any one of the ninth to fifteenth aspects.
[0045]
Therefore, by causing a computer to read the program stored in the storage medium, it is possible to obtain the same operation as the invention according to any one of claims 9 to 15.
[0046]
According to a seventeenth aspect of the present invention, there is provided a position shift correction method, wherein a predetermined area of still image data is divided into one or a plurality of rectangular areas, and a pixel value is frequency-converted for each of the rectangular areas and hierarchically compression-encoded. A syntax analysis step of analyzing the syntax of the encoded code string data, and a displacement detection step of detecting a displacement of an image reference point of the current page with respect to a reference page to be compared based on the analysis result of the syntax analysis step. And a page coordinate moving step of moving the image reference point of the page coordinates of the current page so as to match the image reference point of the page coordinates of the reference page according to the position shift amount detected in the position shift amount detection step. ,including.
[0047]
Therefore, the predetermined page of the still image data is subjected to the frequency conversion of the pixel value for each rectangular area and hierarchically compression-encoded, and the current page relative to the reference page detected based on the analysis result of the syntax of the code string data created. The image reference point at the page coordinates of the current page is moved so as to match the image reference point at the page coordinates of the reference page according to the amount of displacement of the image reference point. This makes it possible to correct the displacement of the image reference point of the current page with respect to the reference page without going through complicated processing of decoding and dequantizing the code string data.
[0048]
According to an eighteenth aspect of the present invention, in the position shift correcting method according to the seventeenth aspect, a condition specifying step of specifying a syntax analysis condition in the syntax analysis step is included.
[0049]
Therefore, for example, by arbitrarily specifying the area of the rectangular region, the number of components (color components), the band of the subband, and the like as the parsing conditions, the accuracy of the displacement amount and the detection processing speed can be adjusted according to the user's desire. It becomes possible to optimize.
[0050]
According to a nineteenth aspect of the present invention, in the position shift correction method according to the seventeenth or eighteenth aspect, the position shift amount detecting step determines a packet length of a packet constituting code string data based on an analysis result of the syntax analysis step. A packet length reading step for reading, a packet length storing step for storing the one packet length read in the packet length reading step as the packet length of a reference page to be compared, and a packet length reading step for reading the packet length. And detecting a difference value between the packet length of the current page and the packet length of the reference page as a positional shift amount of an image reference point with respect to the reference page of the current page.
[0051]
Therefore, the amount of displacement of the image reference point of the current page with respect to the reference page is detected by comparing the packet length, which is the code amount of the frequency conversion coefficient value between the current page and the reference page for a predetermined area of the still image data. You. This eliminates the need for a complicated process of decoding the coded frequency transform coefficient value and further performing inverse quantization upon detecting the amount of displacement of the image reference point of the current page with respect to the reference page. It is possible to quickly and accurately determine the amount of displacement of the image reference point of the current page.
[0052]
According to a twentieth aspect of the present invention, in the method of any one of the seventeenth to nineteenth aspects, the rectangular area, which is a division unit, is a tile.
[0053]
Therefore, a discrete wavelet transform can be used as the frequency transform.
[0054]
According to a twenty-first aspect of the present invention, in the position shift correction method according to any one of the seventeenth to nineteenth aspects, the rectangular area as a division unit is a precinct.
[0055]
Therefore, even when the tile division is not performed (all image areas = tiles), it is possible to speed up the detection of the amount of displacement of the image reference point of the current page with respect to the reference page, as in the case of the tile unit. Further, it becomes possible to set the detection unit to an image area smaller than the tile.
[0056]
According to a twenty-second aspect of the present invention, in the position shift correcting method according to any one of the seventeenth to nineteenth aspects, the rectangular area as a division unit is a code block.
[0057]
Therefore, even when the tile division is not performed (all image areas = tiles), it is possible to speed up the detection of the amount of displacement of the image reference point of the current page with respect to the reference page, as in the case of the tile unit. Further, it becomes possible to set the detection unit to an image area smaller than the tile.
[0058]
According to a twenty-third aspect of the present invention, in the position shift correcting method according to any one of the seventeenth to twenty-second aspects, when the shift amount of the image reference point of the current page with respect to the reference page exceeds a predetermined value, The position shift is not corrected by moving the page coordinates in the coordinate moving step.
[0059]
Therefore, for example, by setting the predetermined value to a value that indicates that the document is out of the reading range, the positional deviation correction is executed until the positional deviation can not be corrected by moving the page coordinates. Can be avoided.
[0060]
BEST MODE FOR CARRYING OUT THE INVENTION
One embodiment of the present invention will be described with reference to FIGS.
[0061]
First, the outlines of the “hierarchical encoding algorithm” and the “JPEG2000 algorithm” which are the premise of the present invention will be described.
[0062]
FIG. 1 is a functional block diagram of a system for realizing a hierarchical coding algorithm which is a basic of the JPEG2000 system. This system includes a color space conversion / inverse transformation unit 101, a two-dimensional wavelet transformation / inverse transformation unit 102, a quantization / inverse quantization unit 103, an entropy coding / decoding unit 104, and a tag processing unit 105. It is configured.
[0063]
One of the biggest differences between this system and the conventional JPEG algorithm is the conversion method. In JPEG, discrete cosine transform (DCT: Discrete Cosine Transform) is used, whereas in the hierarchical coding algorithm, a two-dimensional wavelet transform / inverse transform unit 102 uses discrete wavelet transform (DWT: Discrete Wavelet Transform). ing. DWT has an advantage that the image quality in a high compression area is better than DCT, and this is one of the main reasons why DWT was adopted in JPEG2000 which is a successor algorithm of JPEG.
[0064]
Another major difference is that in the hierarchical coding algorithm, a functional block of the tag processing unit 105 is added in order to form a code at the last stage of the system. The tag processing unit 105 generates compressed data as code string data at the time of image compression operation, and interprets code string data required for decompression at the time of decompression operation. The JPEG2000 can realize various convenient functions by using the code string data. For example, the compression / expansion operation of a still image can be freely stopped at an arbitrary layer (decomposition level) corresponding to octave division in a DWT on a block basis (see FIG. 3 described later).
[0065]
In many cases, a color space conversion / inverse conversion 101 is connected to the input / output portion of the original image. For example, an RGB color system composed of R (red) / G (green) / B (blue) components of a primary color system, and Y (yellow) / M (magenta) / C (cyan) components of a complementary color system The conversion or inverse conversion from the YMC color system to the YUV or YCbCr color system corresponds to this.
[0066]
Next, the JPEG2000 algorithm will be described.
[0067]
Generally, in a color image, as shown in FIG. 2, each component 111 (here, the RGB primary color system) of the original image is divided by a rectangular area. The divided rectangular area is generally called a block or a tile. In JPEG2000, it is generally called a tile. Hereinafter, such a divided rectangular area is referred to as a tile. (In the example of FIG. 2, each component 111 is divided into a total of 16 rectangular tiles 112, 4 × 4 vertically and horizontally.) When such individual tiles 112 (in the example of FIG. 2, R00, R01,..., R15 / G00, G01,..., G15 / B00, B01,. Is the basic unit of Therefore, the compression / decompression operation of the image data is performed independently for each component and for each tile 112.
[0068]
At the time of encoding image data, the data of each tile 112 of each component 111 is input to the color space conversion / inverse conversion unit 101 of FIG. 1 and subjected to color space conversion. A dimensional wavelet transform (forward transform) is performed, and spatial division into frequency bands is performed.
[0069]
FIG. 3 shows subbands at each decomposition level when the number of decomposition levels is three. That is, a two-dimensional wavelet transform is performed on the tile original image (0LL) (decomposition level 0) obtained by dividing the original image into tiles, and the subbands (1LL, 1HL, 1LH) indicated by the decomposition level 1 are obtained. , 1HH). Subsequently, two-dimensional wavelet transform is performed on the low-frequency component 1LL in this layer to separate the subbands (2LL, 2HL, 2LH, 2HH) shown in the decomposition level 2. Similarly, two-dimensional wavelet transform is performed on the low-frequency component 2LL in the same manner to separate the sub-bands (3LL, 3HL, 3LH, 3HH) shown in the decomposition level 3. In FIG. 3, the subbands to be coded at each decomposition level are shaded. For example, when the number of decomposition levels is 3, the subbands (3HL, 3LH, 3HH, 2HL, 2LH, 2HH, 1HL, 1LH, 1HH) indicated by shading are to be encoded, and the 3LL subbands are encoded. Is not converted.
[0070]
Next, bits to be encoded are determined in the designated order of encoding, and the quantization / inverse quantization unit 103 shown in FIG. 1 generates a context from bits around the target bits.
[0071]
The wavelet coefficients after the quantization process are divided into non-overlapping rectangles called “precincts” for each subband. This was introduced to make efficient use of memory in the implementation. As shown in FIG. 4, one precinct is formed of three spatially coincident rectangular areas. Further, each precinct is divided into non-overlapping rectangular "code blocks". This is a basic unit when performing entropy coding.
[0072]
The coefficient value after wavelet transform can be quantized and encoded as it is. However, in JPEG2000, in order to increase the encoding efficiency, the coefficient value is decomposed into “bit plane” units, and each pixel or code block is decomposed. "Bit planes" can be ranked.
[0073]
Here, FIG. 5 is an explanatory diagram showing an example of a procedure for prioritizing bit planes. As shown in FIG. 5, in this example, the original image (32 × 32 pixels) is divided into four 16 × 16 pixel tiles, and the size of the precinct of the decomposition level 1 and the size of the code block are as follows. Each has 8 × 8 pixels and 4 × 4 pixels. The numbers of precincts and code blocks are assigned in raster order. In this example, the precincts are assigned numbers 0 to 3, and the code blocks are assigned numbers 0 to 3. The pixel expansion outside the tile boundary is performed by using a mirroring method, performing a wavelet transform using a reversible (5, 3) filter, and obtaining a wavelet coefficient value of decomposition level 1.
[0074]
FIG. 5 also shows an explanatory diagram showing an example of a typical “layer” configuration concept of tile 0 / precinct 3 / code block 3. The converted code block is divided into subbands (1LL, 1HL, 1LH, 1HH), and each subband is assigned a wavelet coefficient value.
[0075]
The layer structure is easy to understand when the wavelet coefficient value is viewed from the horizontal direction (bit plane direction). One layer is composed of an arbitrary number of bit planes. In this example, layers 0, 1, 2, and 3 are made up of 1, 3, 1, and 3 bit planes, respectively. A layer including a bit plane closer to LSB (Least Significant Bit: Least Significant Bit) is subject to quantization first, and conversely, a layer closer to MSB (Most Significant Bit: Most Significant Bit) is quantized to the end. It will remain without being. A method of discarding from a layer close to the LSB is called truncation, and it is possible to finely control the quantization rate.
[0076]
The entropy encoding / decoding unit 104 shown in FIG. 1 performs encoding on the tile 112 of each component 111 by probability estimation from the context and the target bit. In this way, the encoding process is performed on all the components 111 of the original image in tile 112 units. Finally, the tag processing unit 105 performs a process of combining all the encoded data from the entropy encoding / decoding unit 104 into one piece of code string data and adding a tag thereto.
[0077]
FIG. 6 shows a schematic configuration of one frame of the code string data. At the head of the code string data and the head of the code data (bit stream) of each tile, tag information called a header (main header, tile part header as tile boundary position information, etc.) is provided. This is followed by coded data for each tile. Note that the main header (Main header) describes coding parameters and quantization parameters. Then, a tag (end of codestream) is placed again at the end of the code string data. FIG. 7 shows a code stream structure in which packets containing encoded wavelet coefficient values are represented for each subband. As shown in FIG. 7, the same packet sequence structure is obtained even if the division processing using tiles is performed or the division processing is not performed using tiles.
[0078]
On the other hand, when the encoded data is decoded, the image data is generated from the code string data of each tile 112 of each component 111, contrary to the encoding of the image data. In this case, the tag processing unit 105 interprets the tag information added to the code string data input from the outside, decomposes the code string data into code string data of each tile 112 of each component 111, and A decoding process (decompression process) is performed for each code string data of each tile 112. At this time, the positions of the bits to be decoded are determined in the order based on the tag information in the code string data, and the quantization / dequantization unit 103 sets the peripheral bits of the target bit position (the A context is generated from the sequence of (finished). The entropy coding / decoding unit 104 performs decoding by probability estimation from the context and the code string data, generates a target bit, and writes it to the position of the target bit. Since the data decoded in this way is spatially divided for each frequency band, the two-dimensional wavelet transform / inverse transform unit 102 performs an inverse two-dimensional wavelet transform on the data to obtain each component of the image data. The tile is restored. The restored data is converted by the color space conversion / inverse conversion unit 101 into the original color system image data.
[0079]
The above is the outline of the “JPEG2000 algorithm”.
[0080]
Hereinafter, an embodiment of the present invention will be described. Here, an example relating to an image compression / decompression technique represented by JPEG2000 will be described, but needless to say, the present invention is not limited to the content of the following description.
[0081]
The server computer and the client computer according to the present embodiment perform image processing by being operation-controlled by an image processing program installed on the computer or interpreted and executed. In the present embodiment, a storage medium that stores such an image processing program is also introduced.
[0082]
FIG. 8 is a schematic diagram illustrating a system configuration example according to the present embodiment.
[0083]
In the image data processing system according to the present embodiment, a server client system 1 in which a plurality of client computers 4 as image processing apparatuses are connected to a server computer 2 via a network 3 such as a LAN (Local Area Network) is assumed. The server client system 1 is provided with an environment in which an image input device 5 such as a scanner or a digital camera and an image output device 6 such as a printer can be shared on a network 3. Further, an MFP 7 called a multifunction peripheral may be connected to the network 3, and an environment may be constructed such that the MFP 7 functions as the image input device 5 or the image output device 6.
[0084]
Such a server client system 1 is configured to be able to perform data communication with another server client system 1 via, for example, an intranet 8, and is configured to be able to perform data communication with an external environment via an Internet communication network 9.
[0085]
The server computer 2 includes a document management server 2a and a data conversion server 2b. The document management server 2a exhibits a document management function of storing image images of various documents as image data. The data conversion server 2b exerts a data conversion function such as extracting text data by performing an OCR (Optical Character Reader) process on the image data.
[0086]
In the following, a description will be given of a client computer 4 which is an image processing device that exhibits the characteristic functions of the present invention.
[0087]
FIG. 9 is a module configuration diagram of the client computer 4 as the image processing device according to the present embodiment. The client computer 4 includes a CPU (Central Processing Unit) 11 for performing information processing, a ROM (Read Only Memory) 12 for storing information, a primary storage device 14 such as a RAM (Random Access Memory) 13, and a storage for storing a compression code to be described later. A secondary storage device 16 such as a hard disk drive (HDD) 15 as a unit, a removable disk device 17 such as a CD-ROM drive for storing information, distributing information to the outside, and obtaining information from the outside, a network A network interface 18 for transmitting information through communication with the image input device 5 and other external computers via the CRT 3; a CRT (Cathode Ray Tube) or an LCD for displaying the progress of processing and results to the operator; It comprises a display device 19 such as a Liquid Crystal Display, a keyboard 20 for the operator to input commands and information to the CPU 11, a pointing device 21 such as a mouse, and the like, and data transmitted and received between these units. Are operated by the bus controller 22.
[0088]
In such a client computer 4, when the user turns on the power, the CPU 11 starts a program called a loader in the ROM 12, reads a program called an operating system, which manages the hardware and software of the computer, from the HDD 15 into the RAM 13. Start. Such an operating system starts a program, reads information, and saves information in response to a user operation. As typical operating systems, Windows (registered trademark), UNIX (registered trademark), and the like are known. The operation programs running on these operating systems are called application programs.
[0089]
Here, the client computer 4 stores an image processing program in the HDD 15 as an application program. In this sense, the HDD 15 functions as a storage medium that stores the image processing program.
[0090]
Generally, an operation program installed in the secondary storage device 16 such as the HDD 15 of the client computer 4 is recorded on an optical information recording medium such as a CD-ROM or a DVD-ROM or a magnetic medium such as an FD. Then, the recorded operation program is installed in the secondary storage device 16 such as the HDD 15. Therefore, a portable storage medium such as an optical information recording medium such as a CD-ROM or a magnetic medium such as an FD can be a storage medium for storing the image processing program. Further, the image processing program may be fetched from outside via, for example, the network interface 18 and installed in the secondary storage device 16 such as the HDD 15.
[0091]
When the image processing program running on the operating system is activated, the client computer 4 causes the CPU 11 to execute various arithmetic processes according to the image processing program and control each unit intensively. Among the various arithmetic processes executed by the CPU 11 of the client computer 4, the characteristic processes of the present embodiment will be described below.
[0092]
Here, functions realized by various arithmetic processes executed by the CPU 11 of the client computer 4 will be described. As shown in FIG. 10, a client computer 4 serving as an image processing device includes an image compression device 4 a that compresses and encodes image data read by an image input device 5, and a position shift of an input document read by the image input device 5. The functions of the position error correction device 4b for correcting the error and the various functions are realized by various arithmetic processes executed by the CPU 11.
[0093]
The image compression device 4a encodes digital image data by JPEG using DCT for frequency conversion or JPEG2000 algorithm using DWT for frequency conversion. The image compression device 4a according to the present embodiment compresses and encodes a digital pixel value signal of an image according to the “JPEG2000 algorithm”. Note that, regarding the compression encoding processing according to the “JPEG2000 algorithm”, the spatial transform / inverse transform unit 101, the two-dimensional wavelet transform / inverse transform unit 102, the quantization / inverse quantize unit 103, the entropy code shown in FIG. The description of the encryption / decryption unit 104 and the tag processing unit 105 has been described above, and a description thereof will be omitted. By the processing in the image compression device 4a, the image data of each of the R, G, and B components of the original image is divided into one or a plurality (usually, a plurality) of tiles for each frame. The data becomes compression-encoded data.
[0094]
The misregistration correction device 4b determines the positional relationship between the “read coordinates” provided on the image input device 5 as shown in FIG. 11 and the “page coordinates” provided on the input document. It is intended to keep it constant between them. That is, the origin position, which is the image reference point of the page coordinates of the plurality of input documents, with respect to the origin position, which is the image reference point of the “read coordinates” of the image input device 5, is made constant. As shown in FIG. 11, the reading range of the image input device 5 is divided into one or a plurality of rectangular areas.
[0095]
The misregistration correction device 4b detects the misregistration of the input document read by the image input device 5 for each document based on the code string data output from the image compression device 4a, and detects the misregistration. It is to be corrected. As shown in FIG. 12, the displacement correcting device 4b includes a code string input means 41 for receiving a code string input, a syntax analyzing means 42, a displacement amount detecting means 43, an extraction condition specifying means 44, a correction determining means 45, It comprises various means of the page coordinate moving means 46. These various means are realized by processing performed by the CPU 11 according to the above-described image processing program. When real-time performance is important, it is necessary to speed up the processing. To this end, it is desirable to separately provide a logic circuit (not shown) and realize the functions of various units by the operation of the logic circuit.
[0096]
Next, each component of the displacement correcting device 4b will be described.
[0097]
The syntax analysis unit 42 decodes the syntax of the code string data input from the image compression device 4 a, that is, the data described in the header, and outputs “header information” to the displacement detection unit 43. . Here, FIG. 13 is an explanatory diagram showing reading of the header section information by the syntax analysis means 42. As shown in FIG. 13, the data amount of the payload portion, that is, the “packet length” is the sum of the number of frequency conversion coefficient values (the code amount of the frequency conversion coefficient value) and is described in the header portion. Here, the frequency transform coefficient value is a wavelet coefficient value. Then, the syntax analysis unit 42 reads the header part information and outputs it to the positional deviation amount detection unit 43.
[0098]
The extraction condition designating unit 44 provides an area and a component (color component) of a rectangular region for the code string data input from the image compression device 4a in order to provide only necessary and sufficient information to the displacement amount detecting unit 43. It functions as condition specifying means for specifying the number and the sub-band. By arbitrarily specifying the area of the rectangular area, the number of components (color components), and the band of the sub-band in the code string data in this manner, the accuracy of the displacement amount and the detection processing speed can be adjusted according to the user's desire. It is possible to optimize. That is, taking into account the trade-off relationship between the detection accuracy of the displacement amount and the detection processing speed, when emphasizing high speed, focus only on the low-frequency sub-band of the luminance component in a small rectangular area. do it. Conversely, when accurate misregistration correction is required, the area of the rectangular region of interest may be increased, and the sub-bands may be checked up to the high band.
[0099]
The position shift amount detecting means 43 is generally composed of header part information of the code data relating to the current page of the document read by the image input device 5 and header part information of the code data relating to the reference page stored in advance. Are compared with each other to detect the displacement amount of the current page. More specifically, based on the “header information” received from the syntax analysis unit 42, the position deviation amount of the input document read by the image input device 5 is detected for each document and output to the correction determination unit 45. Is what you do. In the case of a color image, if only the luminance component is used, the amount of displacement can be detected more easily and at a higher speed.
[0100]
Here, detection of the amount of displacement of the input document read by the image input device 5 by the displacement amount detecting means 43 will be described. Here, a method for detecting the amount of displacement of the input document read by the image input device 5 based on the data amount of the payload portion, that is, the “packet length” will be described. Here, FIG. 14 is a block diagram showing the configuration of the displacement amount detecting means 43. As shown in FIG. 14, upon receiving the header information, the displacement detecting means 43 reads the packet length data of the input document from the header information (packet length reading means 43a). For the input document to be used as the reference page, the packet length data of the read input document is stored (packet length storage unit 43b). Since the amount of displacement of the input document read by the image input device 5 appears in the amount of change in the code amount, that is, the amount of change in the packet length, it is necessary to determine the difference in the packet length between the current page and the reference page. (Difference detecting means 43 c), it is possible to detect the positional deviation amount of the input document read by the image input device 5.
[0101]
Here, FIG. 15 is an explanatory diagram showing the relationship between the code amount difference and the position shift amount. As shown in FIG. 15, it can be seen that the positional deviation amount of the input document read by the image input device 5 increases as the absolute value of the code amount difference (difference value of packet length) increases. That is, if there is no change or a very small amount of code amount difference (difference value of packet length) between the current page and the reference page, there is no positional deviation between the current page and the reference page or very little. If it is small, it can be considered. Conversely, if the change in the absolute value of the code amount difference (difference value of the packet length) is large, it can be considered that the positional deviation amount between the current page and the reference page is large, or that the types of documents are different. it can.
[0102]
The correction determining unit 45 determines whether to move the page coordinates (positional deviation correction) based on the “positional deviation amount of the input document read by the image input device 5” received from the positional deviation amount detection unit 43. To decide. For example, if the displacement amount is equal to or less than a threshold value specified in advance by the user, the movement of the page coordinates (displacement correction) is not performed. On the other hand, when the displacement exceeds the threshold, the movement of the page coordinates (displacement correction) is performed. That is, when the correction determining unit 45 determines that the positional deviation amount is small and it is not necessary to move the page coordinates (positional deviation correction), the correction determining unit 45 outputs a control signal to that effect to the image input device 5. . If it is determined that the positional deviation amount can be corrected, the correction determining unit 45 determines the “positional deviation amount of the input document read by the image input device 5” for the page coordinate moving unit 46. Output.
[0103]
The page coordinate moving means 46 determines the origin of the page coordinates of the input document in accordance with the “position shift amount of the input document read by the image input device 5” received from the correction determining means 45 based on the image coordinates of the page coordinates of the reference page. It is moved to match the point.
[0104]
The details of the position shift correction processing by the position shift correction device 4b described above will be described in more detail with reference to the flowchart of FIG. 16 showing the flow of the position shift correction processing by the position shift correction device 4b. This misregistration correction processing is executed at the time of pre-scanning before the reading (main scan) of the entire area of the document by the image input device 5 is performed. In this pre-scan, as shown in FIG. 17, instead of reading the entire area of the document, four areas formed at four corners and located at four corners defined on the read coordinates are formed. The image is read as an area for detecting a displacement, and compression-encoded by the image compression device 4a. When the code string is in the JPEG2000 format, a tile, a precinct, or a code block can be used as a rectangular area.
[0105]
As shown in FIG. 16, in the position shift correction processing, first, one document read by the image input device 5 is set as a reference page, and a compression code of each area for position shift detection of the reference page is obtained (step (Y in S1), the code amount of each area is calculated and stored (step S2). By the above processing, the code amount of each area for detecting the displacement of the reference page is stored and held.
[0106]
In such a state, another document read by the image input device 5 is set as the current page, and the compression code of each area for detecting the displacement of the current page is obtained (Y in step S4). The code amount is calculated (step S5).
[0107]
In the following step S5, the code amount of each area of the current page is compared with the code amount of each area of the reference page to calculate the amount of displacement.
[0108]
Here, FIG. 18 is an example showing “a positional shift amount of the input document read by the image input device 5” between the reference page and the current page. In the example shown in FIG. 18, comparing the area for detecting the displacement of the reference page with the area for detecting the displacement of the current page, it can be seen that the page coordinates are slightly shifted. As described above, since such a shift amount appears in the change amount of the code amount, that is, the change amount of the packet length, it is necessary to calculate the difference in the packet length between the current page area and the reference page area. Can be detected.
[0109]
When the displacement amount is calculated in step S5, the calculated displacement amount is compared with a predetermined upper limit value (step S6). This upper limit is set so that, for example, it is possible to recognize that the document has run out of the reading range. If the displacement exceeds the upper limit (N in step S6), a control signal for instructing the image input device 5 to re-read the document is output, and each area for detecting the displacement of the current page is output. (Step S3).
[0110]
On the other hand, if the displacement does not exceed the upper limit (Y in step S6), the threshold value designated by the user and the displacement are compared (step S7).
[0111]
If the displacement amount exceeds the threshold value (N in step S7), the process proceeds to step S8, in which the page coordinates are moved (displacement correction). The movement of the page coordinates is performed by shifting the pixel value (given for each read coordinate) of the current page read by the image input device 5 by the amount of positional deviation.
[0112]
Then, when the compression code of each area for detecting the displacement of the current page after the movement of the page coordinates is obtained (Y in step S4), the code amount of each area is calculated (step S5), and the displacement amount becomes a threshold. Until the following (Y in step S7), the movement of the page coordinates in step S8, that is, the displacement correction is repeated. FIG. 19 shows the current page before the positional deviation correction and after the completion of the positional deviation correction. In the example shown in FIG. 19, the displacement of the current page is only in the horizontal and vertical directions. The misregistration correction device 4b according to the present embodiment can cope with a case where a document to be read is inclined with respect to the read coordinates. It goes without saying that the relationship between the displacement amount and the displacement direction needs to be determined in advance in detail.
[0113]
FIG. 20 shows the relationship between the amount of displacement and the code amount difference before and after the completion of the displacement correction. As shown in FIG. 20, in order to more efficiently obtain the displacement amount, the first displacement amount detection processing is performed only on the low frequency sub-band, and the sub-bands are sequentially moved to the high frequency band. The method is effective.
[0114]
If the amount of displacement is equal to or smaller than the threshold value specified in advance by the user (Y in step S7), the image input device 5 is caused to execute the main scan process of the original (the process of reading the entire area of the current page). Is transmitted (step S9), and the pre-scan process ends.
[0115]
Here, the current page with respect to the reference page detected based on the analysis result of the syntax of the code string data created by frequency-converting the pixel value of each of the predetermined areas of the still image data for each rectangular area and hierarchically compressing and encoding them Is moved so that the image reference point of the page coordinates of the current page coincides with the image reference point of the page coordinates of the reference page. This makes it possible to correct the displacement of the image reference point of the current page with respect to the reference page without going through complicated processing of decoding and dequantizing the code string data.
[0116]
In the present embodiment, the case where the original image is subjected to the tile division processing has been described, but the present invention is not limited to this. Even when the tile division is not performed on the original image, if the precinct or the code block is used as a rectangular area, the positional deviation amount of the image reference point of the current page with respect to the reference page can be calculated as in the case of performing the tile division. It is possible to detect.
[0117]
【The invention's effect】
According to the misalignment correction apparatus of the present invention, a predetermined area of the still image data is divided into one or a plurality of rectangular areas, and a pixel value is frequency-converted for each of the rectangular areas and hierarchically compression-encoded. Parsing means for analyzing the syntax of the code string data created by the method, and a displacement amount for detecting a displacement amount of the image reference point of the current page with respect to the reference page to be compared based on the analysis result of the syntax analyzing means Detecting means and page coordinate movement for moving the image reference point of the page coordinates of the current page so as to match the image reference point of the page coordinates of the reference page in accordance with the amount of displacement detected by the displacement amount detecting means. Means for analyzing the syntax of code string data created by frequency-converting pixel values of a predetermined area of the still image data for each rectangular area and compressively coding them hierarchically. By moving the image reference point of the page coordinates of the current page so as to match the image reference point of the page coordinates of the reference page in accordance with the amount of displacement of the image reference point of the current page with respect to the reference page detected based on It is possible to correct the displacement of the image reference point of the current page with respect to the reference page without going through complicated processing of decoding and dequantizing the code string data.
[0118]
According to a second aspect of the present invention, in the position shift correcting apparatus according to the first aspect, there is provided condition specifying means for specifying syntax analysis conditions in the syntax analysis means. By arbitrarily specifying the number of (color components), sub-bands, and the like, it is possible to optimize the accuracy of the displacement amount and the detection processing speed according to the user's desire.
[0119]
According to a third aspect of the present invention, in the position shift correcting device according to the first or second aspect, the position shift amount detecting unit is configured to determine a packet of a packet constituting code string data based on an analysis result of the syntax analyzing unit. Packet length reading means for reading the length, packet length storage means for storing the one packet length read by the packet length reading means as the packet length of the reference page to be compared, and packet length reading means Difference detecting means for detecting a difference value between the read packet length of the current page and the packet length of the reference page as a positional deviation amount of an image reference point with respect to the reference page of the current page, The amount of misalignment of the image reference point of the current page is calculated based on the frequency between the current page and the reference page for a predetermined area of the still image data. By detecting by comparing the packet length, which is the code amount of the conversion coefficient value, upon detecting the amount of displacement of the image reference point of the current page with respect to the reference page, the encoded frequency conversion coefficient value is decoded, and Since the complicated process of inverse quantization becomes unnecessary, the amount of displacement of the image reference point of the current page with respect to the reference page can be quickly and accurately obtained.
[0120]
According to the fourth aspect of the present invention, in the position shift correcting apparatus according to any one of the first to third aspects, the rectangular area as a division unit is a tile, and thus a discrete wavelet transform is used as a frequency transform. Can be.
[0121]
According to the fifth aspect of the present invention, in the position shift correcting apparatus according to any one of the first to third aspects, the rectangular area as a division unit is precinct, and is not divided into tiles (all image areas). = Tile), it is possible to speed up the detection of the displacement of the image reference point of the current page with respect to the reference page in the same manner as in the tile unit, and to set the detection unit to an image area smaller than the tile. Can be.
[0122]
According to a sixth aspect of the present invention, in the position shift correcting apparatus according to any one of the first to third aspects, when the rectangular area as a division unit is a code block, the rectangular area is not divided into tiles. Similarly to the tile unit, it is possible to speed up the detection of the displacement amount of the image reference point of the current page with respect to the reference page, and to set the detection unit to an image area smaller than the tile. can do.
[0123]
According to a seventh aspect of the present invention, in the position shift correcting apparatus according to any one of the first to sixth aspects, when the shift amount of the image reference point of the current page with respect to the reference page exceeds a predetermined value, By not performing the position shift correction by the movement of the page coordinates by the page coordinate movement means, for example, by setting a predetermined value to a value that can be recognized that the original is out of the reading range, the movement of the page coordinates is improved. It is possible to avoid executing the position shift correction even when the position shift correction due to is not possible.
[0124]
According to the image processing apparatus of the present invention, an image compression apparatus divides still image data into one or a plurality of rectangular areas, frequency-converts pixel values for each of the rectangular areas, and hierarchically compresses and codes the image data. 8. The image compression apparatus according to claim 1, wherein a displacement of an image reference point of a current page with respect to a reference page is corrected based on code string data of a predetermined area of the still image data compression-encoded by the image compression apparatus. With the provision of the misalignment correction device, it is possible to provide an image processing device having the same operation and effect as the invention according to any one of claims 1 to 7 when compressing an image.
[0125]
According to a ninth aspect of the present invention, there is provided a program which is installed on a computer or interpreted and executed, wherein the predetermined area of the still image data is divided into one or a plurality of rectangular areas. Then, based on the analysis result of the syntax analysis function, a syntax analysis function for analyzing the syntax of the code string data created by frequency-converting and hierarchically compressing and encoding the pixel value for each rectangular area, A position shift amount detecting function for detecting a position shift amount of an image reference point of the current page with respect to a reference page, and an image reference point of a page coordinate of the current page according to the position shift amount detected by the position shift amount detection function. And a page coordinate moving function for moving the still image data so as to match the image reference point of the page coordinates of the reference page. Is calculated based on the analysis result of the syntax of the code string data created by frequency-converting the pixel value for each rectangular area and hierarchically compressing and encoding the positional deviation amount of the image reference point of the current page with respect to the reference page detected based on the analysis result. Accordingly, by moving the image reference point of the page coordinates of the current page so as to match the image reference point of the page coordinates of the reference page, the reference can be performed without going through a complicated process of decoding and dequantizing the code string data. The displacement of the image reference point of the current page with respect to the page can be corrected.
[0126]
According to the tenth aspect of the present invention, in the program according to the ninth aspect, the computer causes the computer to execute a condition specifying function for specifying a parsing condition in the parsing function. By arbitrarily specifying the number of components (color components), the band of the sub-band, and the like, the accuracy of the amount of displacement and the detection processing speed can be optimized according to the user's desire.
[0127]
According to an eleventh aspect of the present invention, in the program according to the ninth or tenth aspect, the displacement detection function reads a packet length of a packet constituting code string data based on an analysis result of the syntax analysis function. A packet length reading function, a packet length storage function of storing the one packet length read by the packet length reading function as the packet length of a reference page to be compared, and a packet length reading function read by the packet length reading function. Causing the computer to execute a difference detection function of detecting a difference value between the packet length of the current page and the packet length of the reference page as a positional shift amount of an image reference point with respect to the reference page of the current page. Relative to the current page for a predetermined area of the still image data. Detected by comparing the packet length, which is the code amount of the frequency conversion coefficient value with the reference page, to detect the amount of displacement of the image reference point of the current page with respect to the reference page, the encoded frequency conversion coefficient value Since the complicated process of decoding and inverse quantization is unnecessary, the amount of displacement of the image reference point of the current page with respect to the reference page can be quickly and accurately obtained.
[0128]
According to the twelfth aspect of the present invention, in the program according to any one of the ninth to eleventh aspects, since the rectangular area as a division unit is a tile, a discrete wavelet transform can be used as a frequency transform.
[0129]
According to a thirteenth aspect of the present invention, in the program according to any one of the ninth to eleventh aspects, the rectangular area as a division unit is a precinct, so that tile division is not performed (all image area = tile). In addition, similarly to the tile unit, it is possible to speed up the detection of the displacement amount of the image reference point of the current page with respect to the reference page, and it is possible to set the detection unit to an image area smaller than the tile.
[0130]
According to a fourteenth aspect of the present invention, in the program according to any one of the ninth to eleventh aspects, the rectangular area, which is a unit of division, is a code block, and is not tile-divided (all image areas = Similarly to the tile unit, it is possible to speed up the detection of the displacement amount of the image reference point of the current page with respect to the reference page, and to set the detection unit to an image area smaller than the tile. it can.
[0131]
According to a fifteenth aspect of the present invention, in the program according to any one of the ninth to fourteenth aspects, when the positional shift amount of the image reference point of the current page with respect to the reference page exceeds a predetermined value, the page coordinates are set. By not allowing the computer to execute the position shift correction by moving the page coordinates by the movement function, for example, by setting a predetermined value to a value that indicates that the original is out of the reading range, the movement of the page coordinates can be improved. It is possible to avoid executing the position shift correction even when the position shift correction due to is not possible.
[0132]
According to the storage medium of the present invention, since the program according to any one of claims 9 to 15 is stored, the program stored in the storage medium can be read by a computer. The same function and effect as the invention described in any one of Items 9 to 15 can be obtained.
[0133]
According to the misalignment correction method of the present invention, a predetermined area of the still image data is divided into one or a plurality of rectangular areas, and a pixel value is frequency-converted for each of the rectangular areas and hierarchically compression-encoded. A parsing step of parsing the syntax of the code string data created by the method, and a displacement amount for detecting a displacement amount of the image reference point of the current page with respect to a reference page to be compared based on the analysis result of the parsing step. A detection step, and a page coordinate movement for moving the image reference point of the page coordinate of the current page so as to match the image reference point of the page coordinate of the reference page in accordance with the displacement detected in the displacement detection step. And analyzing the syntax of code string data created by frequency-converting pixel values of each predetermined area of the still image data for each rectangular area and hierarchically compressing and encoding them. Moving the image reference point of the page coordinates of the current page to match the image reference point of the page coordinates of the reference page in accordance with the amount of displacement of the image reference point of the current page with respect to the reference page detected based on the result. Accordingly, it is possible to correct the displacement of the image reference point of the current page with respect to the reference page without going through complicated processing of decoding and dequantizing the code string data.
[0134]
According to the eighteenth aspect of the present invention, in the position shift correcting method according to the seventeenth aspect, a condition specifying step of specifying a parsing condition in the parsing step is included. By arbitrarily specifying the number of (color components), sub-bands, and the like, it is possible to optimize the accuracy of the displacement amount and the detection processing speed according to the user's desire.
[0135]
According to a nineteenth aspect of the present invention, in the position shift correction method according to the seventeenth or the eighteenth aspect, the position shift amount detecting step is a packet of a packet constituting code string data based on an analysis result of the syntax analysis step. A packet length reading step of reading a length, a packet length storing step of storing the one packet length read in the packet length reading step as the packet length of a reference page to be compared, and a packet length reading step. Detecting a difference value between the read packet length of the current page and the packet length of the reference page as a positional shift amount of an image reference point with respect to the reference page of the current page. The amount of displacement of the image reference point of the current page is determined by comparing the current page and the reference page for a predetermined area of the still image data. By detecting by comparing the packet length, which is the code amount of the wave number conversion coefficient value, upon detecting the positional shift amount of the image reference point of the current page with respect to the reference page, decode the encoded frequency conversion coefficient value, Further, since a complicated process of inverse quantization is not required, the positional shift amount of the image reference point of the current page with respect to the reference page can be obtained quickly and accurately.
[0136]
According to a twentieth aspect of the present invention, in the positional deviation correction method according to any one of the seventeenth to nineteenth aspects, the rectangular area as a division unit is a tile, so that a discrete wavelet transform is used as a frequency transform. Can be.
[0137]
According to the twenty-first aspect of the present invention, in the position shift correction method according to any one of the seventeenth to nineteenth aspects, the rectangular area, which is a unit of division, is not divided into tiles due to being a precinct (all image areas). = Tile), it is possible to speed up the detection of the displacement of the image reference point of the current page with respect to the reference page in the same manner as in the tile unit, and to set the detection unit to an image area smaller than the tile. Can be.
[0138]
According to a twenty-second aspect of the present invention, in the position shift correction method according to any one of the seventeenth to nineteenth aspects, when the rectangular area that is a division unit is a code block, tile division is not performed. Similarly to the tile unit, it is possible to speed up the detection of the displacement amount of the image reference point of the current page with respect to the reference page, and to set the detection unit to an image area smaller than the tile. can do.
[0139]
According to a twenty-third aspect of the present invention, in the misalignment correction method according to any one of the seventeenth to twenty-second aspects, when the misalignment amount of the image reference point of the current page with respect to the reference page exceeds a predetermined value, By not performing the position shift correction by the movement of the page coordinates in the page coordinate movement step, for example, by setting a predetermined value to a value at which the document is found to be out of the reading range, the movement of the page coordinates is improved. It is possible to avoid executing the position shift correction until the position shift correction due to is impossible.
[Brief description of the drawings]
FIG. 1 is a functional block diagram of a system for realizing a hierarchical coding algorithm which is a basis of the JPEG2000 system on which the present invention is based.
FIG. 2 is an explanatory diagram showing a divided rectangular area of each component of an original image.
FIG. 3 is an explanatory diagram showing subbands at each decomposition level when the number of decomposition levels is three.
FIG. 4 is an explanatory diagram showing a precinct.
FIG. 5 is an explanatory diagram showing an example of a procedure for ranking bit planes.
FIG. 6 is an explanatory diagram showing a schematic configuration of one frame of code string data.
FIG. 7 is an explanatory diagram showing a code stream structure in which packets containing encoded wavelet coefficient values are represented for each subband.
FIG. 8 is a schematic diagram showing a system construction example according to an embodiment of the present invention.
FIG. 9 is a module configuration diagram of a client computer as an image processing apparatus.
FIG. 10 is a functional block diagram illustrating a configuration of an image processing apparatus.
FIG. 11 is an explanatory diagram showing a positional relationship between “read coordinates” provided on the image input device and “page coordinates” provided on an input document.
FIG. 12 is a functional block diagram illustrating a configuration of a position shift correction device.
FIG. 13 is an explanatory diagram showing reading of header section information by the syntax analysis means.
FIG. 14 is a block diagram showing a configuration of a displacement amount detecting means.
FIG. 15 is an explanatory diagram showing a relationship between a code amount difference and a position shift amount.
FIG. 16 is a flowchart illustrating a flow of a position shift correction process performed by the position shift correction device.
FIG. 17 is an explanatory diagram showing each area for detecting a position shift.
FIG. 18 is an explanatory diagram illustrating an example of “a positional shift amount of an input document read by an image input device” between a reference page and a current page.
FIG. 19 is an explanatory diagram showing a current page before position shift correction and after position shift correction is completed.
FIG. 20 is an explanatory diagram showing a relationship between a displacement amount and a code amount difference before and after completion of the displacement correction.
FIG. 21 is an explanatory diagram illustrating a positional relationship between “read coordinates” provided on the image input device and “page coordinates” provided on an input document.
[Explanation of symbols]
4 Image processing device
4a Image compression device
4b Position shift correction device
15 Storage media
42 Syntax analysis means
43 Position shift detecting means
44 Condition specifying means
46 Page coordinate movement means
43a Packet length reading means
43b Packet length storage means
43c Difference detection means

Claims (23)

Syntactic analysis means for analyzing a syntax of code string data created by dividing a predetermined area of the still image data into one or a plurality of rectangular areas, frequency-converting pixel values for each of the rectangular areas, and hierarchically compressively encoding the pixel values; ,
A displacement amount detecting means for detecting a displacement amount of an image reference point of a current page with respect to a reference page to be compared, based on an analysis result of the syntax analyzing means;
Page coordinate moving means for moving the image reference point of the page coordinates of the current page so as to match the image reference point of the page coordinates of the reference page, in accordance with the position shift amount detected by the position shift amount detecting means,
Misalignment correction device comprising: 2. The apparatus according to claim 1, further comprising condition specifying means for specifying a syntax analysis condition in said syntax analysis means. The displacement amount detecting means includes:
Packet length reading means for reading a packet length of a packet constituting code string data based on an analysis result of the syntax analysis means;
Packet length storage means for storing the one packet length read by the packet length reading means as the packet length of a reference page to be compared;
Difference detecting means for detecting a difference value between the packet length of the current page read by the packet length reading means and the packet length of the reference page as a positional shift amount of an image reference point with respect to the reference page of the current page;
The position shift correction device according to claim 1 or 2, further comprising: 4. The apparatus according to claim 1, wherein the rectangular area serving as a division unit is a tile. 4. The apparatus according to claim 1, wherein the rectangular area as a division unit is a precinct. 4. The apparatus according to claim 1, wherein the rectangular area as a division unit is a code block. 7. The image forming apparatus according to claim 1, wherein when the displacement of the image reference point of the current page with respect to the reference page exceeds a predetermined value, the displacement of the page coordinates by the page coordinate moving means is not corrected. Misalignment correction device. An image compression apparatus that divides still image data into one or a plurality of rectangular regions, frequency-converts pixel values for each of the rectangular regions, and hierarchically compresses and codes the image data;
8. The image compression apparatus according to claim 1, wherein a displacement of an image reference point of a current page with respect to a reference page is corrected based on code string data of a predetermined area of the still image data compression-encoded by the image compression apparatus. A displacement correction device;
An image processing apparatus comprising: A program installed or interpreted and executed on a computer, wherein the computer has
A syntax analysis function for analyzing the syntax of code string data created by dividing a predetermined area of the still image data into one or a plurality of rectangular areas, frequency-converting pixel values for each of the rectangular areas, and hierarchically compressively encoding the pixel values; ,
A displacement detection function for detecting a displacement of an image reference point of the current page with respect to a reference page to be compared based on an analysis result of the syntax analysis function;
A page coordinate movement function for moving the image reference point of the page coordinate of the current page so as to match the image reference point of the page coordinate of the reference page in accordance with the amount of displacement detected by the displacement amount detection function;
A computer-readable program that causes a computer to execute. The program according to claim 9, wherein the program causes the computer to execute a condition specifying function for specifying a syntax analysis condition in the syntax analysis function. The position shift amount detection function includes:
A packet length reading function for reading a packet length of a packet constituting code string data based on an analysis result of the syntax analysis function;
A packet length storage function of storing the one packet length read by the packet length reading function as the packet length of the reference page to be compared;
A difference detection function of detecting a difference value between the packet length of the current page read by the packet length reading function and the packet length of the reference page as a positional shift amount of an image reference point with respect to the reference page of the current page,
The program according to claim 9, wherein the program is executed by the computer. The program according to any one of claims 9 to 11, wherein the rectangular area as a division unit is a tile. The program according to any one of claims 9 to 11, wherein the rectangular area as a division unit is a precinct. The program according to any one of claims 9 to 11, wherein the rectangular area as a division unit is a code block. 15. The computer according to claim 9, wherein the computer does not execute the correction of the positional deviation by moving the page coordinates by the page coordinate moving function when the positional deviation amount of the image reference point of the current page with respect to the reference page exceeds a predetermined value. The program according to (1). A storage medium storing the program according to claim 9. A syntax analysis step of analyzing a syntax of code string data created by dividing a predetermined area of the still image data into one or a plurality of rectangular areas, frequency-converting pixel values for each of the rectangular areas, and hierarchically compressively encoding the pixel values; ,
A displacement detection step of detecting a displacement of an image reference point of the current page with respect to a reference page to be compared based on an analysis result of the syntax analysis step;
A page coordinate moving step of moving the image reference point of the page coordinates of the current page so as to match the image reference point of the page coordinates of the reference page in accordance with the position shift amount detected in the position shift amount detection step;
Misalignment correction method including: The method according to claim 17, further comprising a condition specifying step of specifying a parsing condition in the parsing step. The displacement amount detecting step includes:
A packet length reading step of reading a packet length of a packet constituting code string data based on an analysis result of the syntax analysis step;
A packet length storing step of storing the one packet length read in the packet length reading step as the packet length of a reference page to be compared;
A difference detection step of detecting a difference value between the packet length of the current page read by the packet length reading step and the packet length of the reference page as a positional shift amount of an image reference point with respect to a reference page of the current page,
19. The method according to claim 17, further comprising: 20. The method according to claim 17, wherein the rectangular area as a division unit is a tile. 20. The method according to claim 17, wherein the rectangular area serving as a division unit is a precinct. 20. The method according to claim 17, wherein the rectangular area serving as a division unit is a code block. 23. The image forming apparatus according to claim 17, wherein when the positional shift amount of the image reference point of the current page with respect to the reference page exceeds a predetermined value, the positional shift is not corrected by moving the page coordinates in the page coordinate moving step. Correction method of position shift.

Images