JP2004159069A - Control method for image processor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control method for an image processor which can suppress an encoded data amount to a prescribed amount when image data are compressed, and which can make an image to have a feeling of unity of image quality in a prescribed unit. <P>SOLUTION: Image data, in which each page is divided into a plurality of blocks, are inputted. The image data are compressed and encoded with first compression conditions in a block unit for every page in a color image encoder 103. The compressed and encoded image data are stored in a hard disk 109. A cumulative value of a data amount when even a prescribed block is compressed and encoded is calculated at a code amount determining part 120. A data amount when the page is totally compressed and encoded is estimated. And, when the estimated data amount is beyond a prescribed value, the compressed and encoded image data are decoded by a color image decoder 104, and they are compressed and encoded again with second compression conditions with a higher compression rate in a color image encoder 107. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to compressing image data at a desired compression ratio.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in an image processing apparatus such as a copying machine having an image memory, an optimal control sequence between units constituting an apparatus has been studied from the viewpoint of improving the productivity of the apparatus. An example of a control sequence for a general color copying machine will be described below. FIG. 16 is a schematic diagram for explaining a configuration of a conventional image processing apparatus having an image memory.
[0003]
In FIG. 16, a reader unit 1200 includes a document feeding unit 1250 having a function of conveying a document sheet, and a scanner unit 1210 having a function of reading a document. The reader unit 1200 is connected to the control unit 1220, and the control unit 1220 is connected to the printer unit 1310. The control device 1220 includes an image memory 1207, controls the document feed unit 1250 and the scanner unit 1210 to read the image data of the document, and controls the print unit 1310 to output the image data to a recording sheet to provide a copy function. I do.
[0004]
Next, control timings of the document feeding unit 1250 and the scanner unit 1210 by the control device 1220 will be described with reference to FIG. FIG. 17 is a diagram showing communication timings of an image reading processing sequence among a control device, a sheet feeding unit, and a scanner unit in a conventional image processing apparatus. Communication between the units is performed by a known technique such as command transmission by serial communication.
[0005]
First, when a read operation start request command is given from the operation unit (not shown) to the control device 1220 (step S1701), the control device 1220 issues a document feed request command to the document feed unit 1250 (step S1702). ). In response to this, the document feeding unit 1250 performs a sheet feeding operation (step S1703), and when the sheet feeding operation is completed, issues a sheet feeding completion command to the control device 1220 (step S1704).
[0006]
In response, the control device 1220 issues a scan start request command to the scanner unit 1210 (step S1705). At the same time, a feed request command for the second original is issued to the original feed unit 1250 (step S1706).
[0007]
The scanner unit 1210 issues a scan preparation completion command in response to the scan start request command (step S1707), starts a scan operation thereafter (step S1708), reads a document, and transfers image data to the control device.
When the scan operation is completed and the image transfer is completed, a scan operation completion command is issued to the control device 1220 and the document feeding unit 1250 (steps S1710 and S1709).
[0008]
The document feeding unit 1250, which has already received the feed request command for the second document, receives the scan operation completion command, discharges the first document, and simultaneously feeds the second document. Can be performed (step S1711).
After the original exchange operation is completed, the original feeding unit 1250 issues a feed completion command for the second original to the control device 1220 (step S1712).
[0009]
The controller 1220, which has received the scan operation completion command for the first document in advance, issues a scan start request command to the scanner unit 1210 in response to the paper supply completion command for the second document (step S1713). ). At the same time, a feed request command for the third document is issued to the document feed unit 1250 (step S1714). Thereafter, the above-described sequence is repeated for the number of documents (steps S1715 to S1719).
[0010]
In the example illustrated in FIG. 17, it is assumed that there are only two documents set in the document feeding unit 1250. Therefore, in response to a feeding request for the third document, the document feeding unit 1250 After performing the sheet discharging operation for the second document (step S1719), a document end notification is issued to the control device 1220 (step S1720), and the reading operation ends.
[0011]
On the other hand, conventionally, when handling color image data, the size of the data amount has been a problem. For example, for a binary image that is large enough to represent a black and white image, a standard color image consisting of 8 bits each for RGB requires 24 times the data amount to represent an image of the same size. Will be. This simply means that 24 times as much memory is required as when a monochrome image is handled, which leads to a large increase in cost.
[0012]
For this reason, a technique has conventionally been adopted in which compression processing is performed on image data to reduce the data capacity, thereby reducing the memory capacity mounted on the device and suppressing an increase in cost. For example, the control unit 1220 includes a circuit for compressing / expanding image data such as an encoding unit 1209 and a decoding unit 1208, and stores image data reduced by compression processing in a memory. By expanding the image data when outputting the image data, the capacity of the image memory can be reduced.
[0013]
[Problems to be solved by the invention]
However, when using a variable-length compression method such as JPEG, which can increase the compression rate and suppress the cost increase, as the method of compressing / expanding image data, the data size after compression until the image compression processing is performed is reduced. Since it is not determined, a situation may occur in which the image does not fit within the desired image size after the image compression.
[0014]
In this case, the sequence as shown in FIG. 17 does not hold, and the control device 1220 waits for the end of the image transfer from the scanner unit 1210 to determine the size of the image data, and then the size exceeds the desired size. In this case, the setting of the encoding unit 1209 is changed so that the image is compressed at a higher compression ratio, and then the image is read again from the same document. FIG. 18 is a diagram showing a communication timing of an image reading process sequence between a control device, a sheet feeding unit, and a scanner unit in a conventional image processing apparatus that performs a rescan process.
[0015]
As shown in FIG. 18, when the image size after compression is larger than the desired size, it may be necessary to read the same document again. Cannot be issued beforehand. Therefore, irrespective of whether or not the reading operation is necessary again, the command for requesting the feed of the next original document cannot be issued unless the image size is definitely determined.
[0016]
Therefore, the sequence is delayed by the response time from when the control device 1220 receives the scan operation completion command to when the next document feed request command is issued, and productivity such as copying deteriorates. There was a problem that it would.
[0017]
When the setting of the encoding unit 1209 is changed for each read original so as to fit in a desired image size, the read image data is read when a plurality of originals are set on the original feed unit 1250. There is a possibility that the setting of the encoding unit 1209 for each document may be different. As a result, although the image sizes are almost the same, the quality and image quality may be different for each image data.
[0018]
For example, even though the user has given one job, among the originals set on the original feeding unit 1250, the read image of one original has a standard image quality, and the read image of another original has a desired image. There is a case where the image is compressed at a higher compression ratio so as to fit in the image size of, and the image quality is relatively deteriorated. That is, there is a problem that the image quality varies in one job.
[0019]
The present invention has been made in view of such circumstances, and when compressing image data, suppresses the amount of encoded data to a predetermined amount, and has a sense of unity of image quality within a predetermined unit. It is an object of the present invention to provide a method for controlling an image processing apparatus capable of forming a displayed image.
[0020]
It is still another object of the present invention to efficiently control reading when a plurality of originals are read for each page and the obtained image data is compressed while achieving the above object.
[0021]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention provides a document reading unit that reads a document and generates image data for one page, and stores image data sequentially generated by the reading unit in a first compression condition for each page. Or a control method for an image processing apparatus comprising: an encoding unit capable of performing compression encoding under a second compression condition having a higher compression ratio; and a storage unit configured to store compression-encoded image data. It is obtained when all the pages are compression-encoded under the first compression condition while the image data for one page generated by the reading unit is being compression-encoded under the first compression condition. An estimating step of estimating the amount of encoded data for one page; and, if the estimated amount of encoded data is equal to or less than a target value, generating image data to be compression-encoded next during the compression-encoding. In addition, When the estimated encoded data amount is equal to or larger than the target value, the original corresponding to the image data in the middle of the encoding is determined during the compression encoding. A decision step of deciding to instruct the reading means to read again; and, when the estimated encoded data amount is equal to or more than a target value, the reading means reads the original again to generate image data. And a re-encoding step of compression-encoding under the compression condition of 2.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0023]
<First embodiment>
FIG. 1 is a block diagram illustrating a configuration of an image processing apparatus according to an embodiment of the present invention. In FIG. 1, a reader unit 200 includes a document feeding unit 250 having a function of transporting a document sheet, and a scanner unit 210 having a function of reading a document. The reader unit 200 is connected to the control device 220. The control device 220 is connected to the printer unit 310 and the page description language rendering unit 121.
[0024]
The control device 220 controls the document feeding unit 250 and the scanner unit 210 to read the image data of the document, and controls the printer unit 310 to output the image data to recording paper to provide a copy function. In FIG. 1, reference numerals 100 and 102 denote selectors for switching an image input system, and reference numeral 112 denotes a selector for switching an image output system. Reference numeral 101 indicates a compression block line buffer, and reference numerals 103 and 107 indicate color image encoders. Further, reference numeral 120 indicates a code amount determination unit, and reference numerals 106 and 110 indicate compression memory buffers. Furthermore, reference numeral 109 denotes a hard disk (HDD), reference numerals 104 and 111 denote color image decoders, and reference numerals 105 and 115 denote expansion block line buffers.
[0025]
A signal input from an image input unit (not shown) is input to the scanner unit 210 and the page description language (PDL) rendering unit 121. In this case, for example, the selector 100 is switched according to the application so as to be input from the scanner unit 210 in the case of a copying machine and from the page description language rendering unit 121 in the case of a printer, and is input to the control device 220.
[0026]
In the compression block line buffer 101, the image is divided into tiles, and the divided tiles are subjected to discrete cosine transform encoding (JPEG), which is encoding of color information, by a color image encoder 103 described later. Here, the size of the tile to be divided is M pixels × N pixels. However, M and N must be multiples of the window size for discrete cosine transform coding. In the JPEG compression method used in the present embodiment, the window size for compression is 8 pixels × 8 pixels. Therefore, if M = N = 32, for example, the tile of 32 pixels × 32 pixels is further divided into 16 windows of 8 × 8 pixels, and JPEG compression is performed in units of 8 × 8 pixels. In the present embodiment, description will be made hereinafter assuming that M = N = 32, but the present invention is not limited to this value.
[0027]
The color image encoder 103 performs a well-known DCT transform on 16 16-pixel × 8-pixel windows included in the 32-pixel × 32-pixel tile image to perform quantization. It is assumed that the quantization coefficient (hereinafter referred to as “quantization matrix”) used at this time can be switched and set for each tile. This switching is performed by a CPU (not shown) generating a selection signal for selecting a plurality of quantization coefficients held in the color image encoder 103 in advance and sending the selection signal to the color image encoder 103. Is
[0028]
The image data encoded as described above is stored as compressed image data on the hard disk 109 via the compression memory buffer 106. On the other hand, when outputting the stored compressed image data from the printer unit 310, the compressed image data stored in the hard disk 109 is read out, decoded and output in the following procedure.
[0029]
First, the color image decoder 104 decodes image data by switching the decoding parameter (inverse quantization matrix) of the image data that has been compressed and stored according to the quantization matrix when the image data was compressed. , And outputs the result to the development block line buffer 105.
[0030]
FIG. 2 is a schematic diagram for explaining a processing procedure of the color image encoder 103 and the color image decoder 104 using DCT according to one embodiment of the present invention. In FIG. 2, reference numeral 20 denotes an image signal input from a not-shown image input device to the color image encoder 103. In the case of a color signal, red (R), green (G), and blue (B) These are signals of 256 gradations in three colors.
[0031]
Further, the image signal input to the color image encoder 103 is converted from an RGB signal into a luminance color difference signal (YCbCr) in the color converter 11. Next, in a discrete cosine transform (DCT) unit, each of the luminance and chrominance signals is subjected to spatial frequency transform (DCT) in units of 8 pixels × 8 pixels.
[0032]
Further, in the quantizer 13, the DCT coefficient is quantized using the set quantization matrix, and the data amount is reduced. Then, in a variable length coding (VLC) unit, the data amount is further reduced by subjecting the quantized value to Huffman coding. The above is the processing procedure in the color image encoder 103. The compressed image data is stored in the compression memory 15 or a large-capacity storage device.
[0033]
On the other hand, the stored image data is decoded by the color image decoder 14 in the following procedure. That is, Huffman decoding is performed by a variable length decoding (VLD) device. Next, the inverse quantizer 17 returns the value to a DCT coefficient value according to the set inverse quantization matrix, and the IDCT unit 18 performs inverse DCT transform to return to a luminance / chrominance signal. Then, in the color converter 19, the luminance / color difference signal is returned to the RGB signal. As a result of the above compression and decoding processing, the color image signal 21 is output to the outside.
[0034]
FIG. 3 is a diagram illustrating an example of an 8 × 8 quantization matrix used for compression processing according to the present embodiment. FIG. 3A shows an example of the quantization matrix T1 applied first, and FIG. 3B shows an example of the quantization matrix T2 applied to increase the compression ratio. Furthermore, in order to obtain a higher compression ratio than the quantization matrix of (b), the quantization matrix T3 of (c) is applied, and to obtain a higher compression ratio than that of (c), (d) of FIG. What is necessary is just to apply the quantization matrix T4.
[0035]
That is, first, image data is compressed (JPEG compression) using the quantization matrix T1, and if a desired compression ratio cannot be achieved, the compression is performed using the quantization matrix T2 as a matrix for coarsening the quantization step. I do. If the desired compression rate cannot be achieved even when the quantization matrix T2 is used, the compression processing is performed using the quantization matrix T3. If the desired compression rate cannot be achieved even still, the compression processing is performed using the quantization matrix T4.
[0036]
In the present embodiment, since four quantization matrices are prepared as described above, re-scanning is performed three times (that is, a maximum of four scans of a document of one page together with the first scan). be able to. In the present invention, by preparing a plurality of quantization matrices having a higher compression ratio in addition to the above, rescanning can be performed again by the number of the prepared quantization matrices.
[0037]
The quantization matrices T1, T2, T3, T4 and their corresponding inverse quantization matrices are stored in advance in the quantization unit 13 and the inverse quantization unit 17 shown in FIG. Which one to use can be switched in tile units according to the quantization matrix at the time of compression.
[0038]
FIG. 4 is a schematic diagram for explaining the data structure of the compressed image data according to the present embodiment. As shown in FIG. 4, header information 41 of the first tile and compressed image data 42 which is DCT-coded image information are stored in order from the head of the data, and the second tile and the third tile have the same configuration. , And the information up to the last tile included in the entire page is written.
[0039]
Here, in the header information of each tile, the data size of the compressed data, the tile number, and the like are recorded, and at the same time, information indicating which quantization matrix was used as the quantization matrix of the image data is also recorded. . When decoding the encoded and recorded data, information on whether the matrix is a quantization matrix T1, T2, T3 or T4 is read with reference to the header information, and an inverse quantization matrix corresponding to each is selected. And perform inverse quantization.
[0040]
FIG. 5 is a conceptual diagram of a management table for managing information of each page of compressed image data according to the present embodiment. As described with reference to FIG. 4, by referring to the header information of each tile, inverse quantization is possible even if quantization is performed using a different quantization matrix for each tile. However, as can be seen from the scan sequence described later, in the present embodiment, if the desired compression ratio is not achieved, the read operation is performed again on the same document after changing the quantization matrix, so that one page Will be quantized using the same quantization matrix.
[0041]
In the header information of each page shown in FIG. 5, the size of the compressed data, the page number, etc. are recorded for each page, and information as to which one was used as the quantization matrix when compressing the page is also recorded. Is done. That is, it is possible to confirm which quantization matrix has been applied to all the tiles in the page by using a common quantization matrix for each page by referring to the management table.
[0042]
Hereinafter, a scan sequence according to the present embodiment will be described. In the present invention, the image size after compression is estimated before the compression processing of the image data is completed, that is, before the control device 220 receives the scan operation completion command. Is issued. That is, before the document feeding unit 250 receives the scan operation completion command from the scanner unit 210, the control device 220 issues a command to request feeding of the next document to the document feeding unit 250. Therefore, the above-described delay of the response time does not occur.
[0043]
Therefore, in the present embodiment, the image data is divided into tiles of 32 pixels × 32 lines, and compression and decompression processing is performed on each tile. Therefore, the size of the compressed image in the middle of one page can be determined by accumulating the image size up to a predetermined number of tiles also by a compression method such as JPEG which originally uses an image for one page. Therefore, by estimating the size of the image data for the rest of the page, it becomes possible to estimate the image size of the entire compressed one page based on a predetermined standard.
[0044]
Therefore, by the following formula, the size of the image data without compression when the image is read up to the predetermined number of tiles, the target compression ratio, the number of tiles of the entire image, the image size of one page after compression Can be represented by a predetermined number of tiles for estimating the image data size and the image data size at the predetermined number of tiles.
[0045]
Sn · Pt> α · (1-x / X) + x · Sc / X (1)
In the equation (1), Sn is the size of image data for one page when not compressed, Pt is the target compression ratio (1.0 is the compression ratio when no compression is performed at all), and α is The compression ratio to be achieved by the image data of the part that has not been read yet, x is a predetermined number of tiles for estimating the image size after compression, X is the number of tiles for one page of image data, and Sc is a predetermined number of tiles. This is the cumulative value of the size of the image data at the time when the number of tiles (x) is read.
[0046]
FIG. 6 is a schematic diagram for explaining tiles of image data to be compressed in the present embodiment. For example, as shown in FIG. 6, in one page of image data consisting of 14 tiles in the main scanning direction and 10 tiles in the sub-scanning direction, up to the hatched tile portion (126 tiles). At the time of reading, the following constants can be applied to each term of Expression (1). However, in order to simplify the calculation, the image of one tile is assumed to be 1 MB when not compressed, and the value of Sc is assumed to be such that the image data of the part that has not been read is not compressed at all even if the encoding process is performed. calculate.
[0047]
That is, Sc = 140 (MB), Pt = 1/8, α = 1.0, x = 126, X = 140, and Sc <3.89 (MB). In this example, the cumulative value of the size of the image data must be always smaller than 3.89 MB until the 126th tile is read out of the 140 tiles of the image data for one page. .
[0048]
Therefore, by determining whether the cumulative value of the size of the image data for the predetermined number of tiles exceeds the predetermined size, it is determined whether the size of the image data for one page is equal to or smaller than a certain size. Can be estimated.
[0049]
7 and 8 show a scan sequence of the control device 220 and a flowchart of the compression size estimation and re-scan processing. That is, FIG. 7 is a flowchart for explaining the image reading process in the control device 220 in the present embodiment.
FIG. 8 is a flowchart for explaining the details of the rescan process in the control device 220 in the present embodiment.
[0050]
The control in the scan sequence of the control device 220 will be described with reference to FIG. First, the control device 220 enters a reading operation start request waiting state (step S701). Next, when a reading operation start request is received from an operation unit (not shown) (Yes), the control device 220 issues a first document feed request command to the document feed unit 250 (step S702). .
[0051]
After that, the control device 220 is in a state of waiting for a paper-feed completion notification from the document feed unit 250 (step S703). Upon receiving the feed completion notification (Yes), the control device 220 issues a scan start request to receive image data, performs encoding processing for each tile image, compresses the tile image, and reads one page of image data. At the stage before finishing (before compressing the image data for one page), the size of the compressed image data for one page is estimated, and according to the estimated value, the next document is read or the same document is read. It is determined whether to change the quantization matrix and scan again (step S704). The details of this process will be described later.
[0052]
Thereafter, the control device 220 enters a state of waiting for a scan completion notification indicating the end of the transfer of the image data from the scanner unit 210 (step S705). Then, when the scan completion notification is received (Yes), it is determined whether or not the document that has just been read is the last document (step S706). When the document is the last document (Yes), the reading operation is terminated. On the other hand, if the document to be read still remains in the document feeding unit 250 (No), the control device 220 shifts to a state of waiting for a notification of completion of feeding the next document (step S1703).
[0053]
Here, control in the compression size estimation and the rescan processing of the control device 220 will be described with reference to FIG. First, before receiving the image data, the control device 220 initializes the accumulated value of the read image data size and the value of the counter for counting the number of tiles of the received image (step S801).
[0054]
Next, the control device 220 determines whether or not the next scan operation is a rescan by referring to a value of a counter for counting the number of rescans (step S802).
As a result, if the rescan is performed (Yes), it is checked whether the number of rescans is equal to or less than a predetermined number (step S803). If the number of rescans is greater than the predetermined number (No), the reading operation is terminated as an error.
The predetermined number depends on the number of quantization matrices prepared in advance.
[0055]
On the other hand, if the number of rescans is equal to or less than the predetermined number (Yes), a quantization coefficient (quantization matrix) is determined according to the number of rescans (step S805). Then, a predetermined number of tiles for estimating the compression ratio and a predetermined size of image data at the number of tiles are determined according to the quantization matrix. If the scan is not the rescan but the first scan for the document, the counter for counting the number of rescans is initialized, and the quantization matrix is set to an initial value (step S804). Then, a predetermined number of tiles for estimating the compression ratio and a predetermined size of image data at the number of tiles are determined according to the quantization matrix.
[0056]
Since the preparation for receiving image data is completed by the above processing, the control device 220 issues a scan start request command to the scanner unit 210 (step S806). After that, the control device 220 enters a state of waiting for a scan preparation completion notification from the scanner unit 210 (step S807). Then, upon receiving the scan preparation completion notification (Yes), the control device 220 enters a state of waiting for tile image reception (step S808). When the tile image is received (Yes), the control device 220 adds the size of the received tile image after being subjected to the encoding process and the compression to the counter for accumulating the size of the image data (step S809).
[0057]
In addition, a counter for counting the number of received tiles is incremented by one (step S810). Then, it is determined whether or not the value of the image data size cumulative value counter exceeds a predetermined size (step S811). As a result, when the accumulated knowledge counter value exceeds the predetermined size (Yes), the control device 220 adds a counter for counting the number of rescans (step S812), and waits for a scan completion notification (step S813).
[0058]
Then, when a scan completion notification is received (Yes), the process shifts to a rescanning sequence (step S801). In this case, since the image reading scan is performed without issuing the next document feed request command to the document feeding unit 250, the image reading scan (rescanning) is performed on the same document as the previously read document. ).
[0059]
On the other hand, if it is determined in step S811 that the accumulated value does not exceed the predetermined size (No), it is checked whether the number of received tiles does not exceed the predetermined number (step S814). As a result, if the number of received tiles does not exceed the predetermined number (No), the control device 220 shifts to a tile image reception waiting state (step S808).
[0060]
If the number of received tiles exceeds the predetermined number (Yes), the control device 220 receives the remaining tiles because the accumulated size of the image data is equal to or smaller than the predetermined size even when the predetermined number of tiles are received. Even if it is not performed, it is estimated that the image data of the one page will be smaller than a certain size, and a command to request feeding of the next document is issued to the document feeding unit (step S815).
[0061]
FIG. 9 is a diagram illustrating communication timing of an image reading processing sequence among the control device 220, the document feeding unit 250, and the scanner unit 210 according to the present embodiment. FIG. 10 is a diagram illustrating communication timings of an image reading processing sequence in which a rescanning process between the control device 220, the document feeding unit 250, and the scanner unit 210 according to the present embodiment occurs.
[0062]
First, the control timing of the document feed unit 250 and the scanner unit 210 by the control device 220 will be described with reference to FIG. Communication between the units is performed by a known technique such as command transmission by serial communication.
[0063]
When a copy operation start request command is given from the operation unit (not shown) to the control device 220 (step S901), the control device 220 issues a document feed request command to the document feed unit 250 (step S902). In response to this, the document feeding unit 250 performs a sheet feeding operation (step S903), and upon completion of the sheet feeding operation, issues a sheet feeding completion command to the control device 220 (step S904).
[0064]
In response, the control device 220 issues a scan start request command to the scanner unit 210 (step S905). After issuing a scan preparation completion command in response to the scan start request command (step S906), the scanner unit 210 starts a scanning operation, reads a document, and transfers image data to the control device (step S907).
[0065]
If the accumulated size of the image data is equal to or smaller than the predetermined size when the image of the predetermined number of tiles is received during the reception of the image data, the control device 220 sends the document A paper feed request command is issued (step S908). When the scanning operation is completed and the image is transferred, a scanning operation completion command is issued to the control device 220 and the document feeding unit 250 (steps S909 and S910).
[0066]
The document feeding unit 250, which has already received the feed request command for the second document, receives the scan operation completion command, discharges the first document, and simultaneously feeds the second document. Can be performed (step S911). After the original exchange operation is completed, the original feeding unit 250 issues a second original feeding completion command to the control device 220 (step S912).
[0067]
The control device 220, which has already received the scan operation completion command for the first document, receives the feed completion command for the second document and issues a scan start request command to the scanner unit 210 (step S913). ). Thereafter, the above-described sequence is repeated for the number of originals (steps S914 to S919).
[0068]
In the example illustrated in FIG. 9, it is assumed that there are only two documents set in the document feeding unit 250, so that the document feeding unit 250 responds to a feeding request for the third document. After performing the sheet discharging operation of the second document (step S919), a document end notification is issued to the control device 220 (step S920), and the reading operation ends.
[0069]
As described above, by estimating the size of one page of the image data during reception of the image data, it is possible to issue a paper feed request command for the next original before receiving the scan completion notification. The delay of the response time as indicated by 18 does not occur.
[0070]
Next, the control timing of the document feeding unit 250 and the scanner unit 210 by the control device 220 when rescanning occurs will be described with reference to FIG. First, when a read operation start request command is given from the operation unit (not shown) to the control device 220 (step S1001), the control device 220 issues a document feed request command to the document feed unit 250 (step S1002). .
[0071]
In response to this, the document feeding unit 250 performs a sheet feeding operation (step S1003), and when the sheet feeding operation is completed, issues a sheet feeding completion command to the control device 220 (step S1004). In response, the control device 220 issues a scan start request command to the scanner unit 210 (step S1005).
[0072]
After issuing a scan preparation completion command in response to the scan start request command (step S1006), the scanner unit 210 starts a scanning operation, reads a document, and transfers image data to the control device (step S1007). If the accumulated size of the image data is larger than the predetermined size before the image of the predetermined number of tiles is received during the reception of the image data, the control device 220 sends the second sheet to the document feeding unit 250. Without issuing a feed request command for the document, the scanner enters a scan operation completion command reception wait state.
[0073]
When the scanning operation is completed and the image transfer is completed, the scanner unit 210 issues a scanning operation completion command to the control device 220 and the document feeding unit 250 (steps S1008 and S1009). In response to this, the control device 220 issues a scan start request command to the scanner unit 210 (step S1010). Here, since the feed request command for the second document has not been issued, the document feed unit 250 does not feed the next document, and as a result, scans the first document again. Will be read. Thereafter, the sequence is the same as the sequence shown in FIG. 9 (steps S1010 to S1022).
[0074]
The communication timing shown in FIG. 10 is different from the case shown in FIG. 9 only in that rescanning is performed, and productivity is reduced by the time required for rescanning. However, the response time delay as shown in FIG. 18 does not occur.
[0075]
In the present embodiment, the case where the input source of the image data is the reader unit 200 has been described. However, even when the input source is the page description language rendering unit 121 in FIG. It goes without saying that you can do it.
[0076]
Next, a characteristic print sequence according to the present embodiment will be described. When a plurality of documents set on the document feed unit 250 are read by the above-described scan sequence, the quantization matrix used for compression may be different depending on each document read image. For example, different quantization matrices may be used, such as one image having a quantization matrix T1, another image having a quantization matrix T2, or T3 and T4.
[0077]
In general, an image compressed using a quantization matrix that can obtain a higher compression rate has a larger degradation of an image upon decoding and has a lower image quality. For this reason, for example, in a bundle of originals input as one job, the quantization matrix T2 is used for only one original even though the quantization matrix T1 is used for the read image of another original. Is used, the deterioration of the image quality of the document image becomes relatively prominent.
[0078]
In order to prevent such a phenomenon, for a plurality of images input as one job in the print sequence, the quantization matrix having the highest compression rate among the quantization matrices used when compressing the images is used. By performing the compression process again, control is performed to equalize the image quality and image quality in one job.
[0079]
FIG. 11 is a block diagram for explaining an image encoding unit and an image decoding unit in a print sequence according to an embodiment of the present invention. The numbers of the individual blocks in FIG. 11 correspond to the numbers of the blocks described in FIG.
[0080]
In FIG. 11, first, at normal time, an image read from the hard disk (HDD) 19 for printing includes a selector 112, a selector 102, a compression memory buffer 110, a color image decoder 111, and a development block line buffer 115. The decoded image data is sent to the printer unit 310 via the path of the printer unit 310 and printed out. At this time, the inverse quantization matrix used in the color image decoder 111 has the highest compression rate among the quantization matrices used in a plurality of images of the print job.
[0081]
When recompression processing is performed to reconcile the image quality in the job (at the time of recompression), the hard disk (HDD) 109, the selector 112, the color image decoder 104, the decompression block line buffer 105, the color The decoded image data is sent to the printer unit 310 via the path of the image encoder 107, the selector 102, the compression memory buffer 110, the color image decoder 111, the expansion block line buffer 115, and the printer unit 310 for printing. Will be out.
[0082]
At this time, the inverse quantization matrix used in the color image decoder 104 uses the one used when each image was compressed in the scan sequence. Also, the quantization matrix used in the color image encoder 107 has the highest compression rate among the quantization matrices used in a plurality of images of the print job. By processing image data using the above-described path using such a quantization matrix, compression processing is performed again on all pages of the job, and image quality in one job, Image quality can be aligned.
[0083]
FIG. 12 is a flowchart for explaining an operation procedure of the image reading process of the control device 220 in the print sequence. First, the control device 220 searches a management table for managing information for each page when the compressed image data showing the concept in FIG. 5 is stored in the hard disk. Then, for the page in the print job, a quantization matrix with the highest compression ratio used at the time of scanning is obtained (step S1201). For example, if the quantization matrix with the highest compression rate used in the job is T4, all the pages in the job are aligned to the image quality compressed by the quantization matrix T4 by the following sequence. Become. However, when all the pages have been compressed by the quantization matrix T1, it is not necessary to perform the recompression processing.
[0084]
Next, the control device 220 sets the quantization matrix with the highest compression rate in the searched job in the color image encoder 107 (step S1202). Thereafter, the control device 220 prepares to sequentially read out the pages of the job to be printed from the hard disk 109. Specifically, the quantization matrix of the next page is obtained by referring to the management table described above (step S1203).
[0085]
Based on the obtained quantization matrix, it is determined whether the page needs to be recompressed (step S1204). As a result, if the obtained quantization matrix is not the one with the highest compression rate in the job, recompression processing is necessary (Yes), and recompression processing is performed. That is, the selectors 112 and 102 are set, and the image data is recompressed by the quantization matrix having the highest compression ratio in the job through the recompression path shown in FIG. 1121 (step S1205). .
[0086]
If the obtained quantization matrix has the highest compression rate in the job, there is no need to perform recompression processing (No), and thus it is printed out as it is via the normal path shown in FIG. 11 ( Step S1206). At the time of printout, both the normal image data and the recompressed image data are decoded by the color image decoder 111 using the inverse quantization matrix having the highest compression ratio in the job.
[0087]
Furthermore, it is determined whether the read page is the last page in the job (step S1207). If it is not the last page (No), the process returns to step S1203. If it is the last page (Yes), the print job ends.
[0088]
That is, in the present embodiment, a document reading unit (for example, a selector 100) that reads a document and generates image data for one page, and converts the image data sequentially generated by the reading unit into a first compression image for each page. Encoding means (for example, the color image encoder 103) capable of performing compression encoding under a condition or a second compression condition having a higher compression ratio, and storage means (for example, for storing compression-encoded image data) , An HDD 109) and a control method thereof. The image processing apparatus compresses and encodes one page of image data generated by the reading unit under the first compression condition while compressing and encoding the image data under the first compression condition. Estimating means (code amount determining unit 120) for estimating the encoded data amount for one page obtained when the estimated encoded data amount is equal to or smaller than the target value. In order to generate image data to be compression-encoded, a decision is made to instruct the reading means to read the next document, and if the estimated amount of encoded data is equal to or greater than the target value, a code is generated during compression encoding. Determining means (CPU) for determining to instruct the reading means to read the document corresponding to the image data in the middle of the conversion again, and reading the document again by the reading means when the estimated encoded data amount is equal to or larger than the target value. Reading Taken and further comprising a re-encoding means (color image coder 107) for compressing and encoding the image data generated by the second compression condition.
[0089]
The present invention also provides an image input unit (selector 100) for inputting image data in which each page is divided into a plurality of blocks, and an encoding unit (color image code) for compressing and encoding the input image data in block units. And an image processing apparatus (control device 220) including a storage unit (HDD 109) for storing compression-encoded image data, wherein the encoding unit (color image encoder 103) Calculation means (compression amount determination unit 120) for compressing and encoding data on a page basis under a first compression condition and calculating a cumulative value of the data amount when up to a predetermined block of one page in image data is compression-encoded. Estimating means (code amount determining unit 120) for estimating the data amount when all the pages are compression-encoded based on the calculated accumulated value of the data amount; Decoding means (color image decoder 104) for decoding the image data which has been compression-encoded based on the compression condition; and, if the estimated data amount is equal to or less than a predetermined value, the image to be compression-encoded next Determining means (CPU) for determining a page of data; and, when the estimated data amount is equal to or greater than a predetermined value, re-compressing the image data of the decoded page under a second compression condition having a higher compression ratio. Encoding means (color image encoder 107).
[0090]
Still further, the present invention is characterized in that the encoding means (color image encoder 103) and the re-encoding means (color image encoder 107) perform compression encoding processing according to the JPEG method.
[0091]
Still further, according to the present invention, the encoding means (color image encoder 103) quantizes the DCT-transformed transform coefficients using a plurality of quantization matrices, so that input image data is compressed differently. It is characterized by compression coding at a rate.
[0092]
Still further, the present invention further includes an information adding unit (CPU) for adding information relating to the first compression condition or the second compression condition when the image data is compression-encoded to the image data, and a storage unit (HDD 109). ) Stores compressed image data to which information on the first compression condition or the second compression condition is added.
[0093]
Furthermore, the present invention is characterized in that it is connected to an image input device (reader unit 200) or a page description language rendering device 121 that reads a document and converts it into image data, and is capable of inputting image data for each page. .
[0094]
<Second embodiment>
In the first embodiment, an embodiment of the present invention has been described using a normal copy job as an example, but the present invention is not limited to this. For example, the effect of the present invention can be utilized even in a function generally called a reduced layout.
This will be described below.
[0095]
FIG. 13 is a schematic diagram for explaining a reduced layout function according to the second embodiment of the present invention. Note that the reduced layout is a function of reducing a plurality of originals, appropriately laying out the originals on one sheet, and outputting. For example, in the case of “4 in 1”, four read originals are reduced by 50%, laid out on one sheet, and output.
[0096]
At this time, if the individual images arranged on the same sheet are compressed using different quantization matrices, the image quality will differ depending on the portion on one sheet. Therefore, in the present invention, the image quality of each image on paper is made uniform by performing recompression processing for each image used for the reduced layout. Hereinafter, control of recompression in the reduced layout according to the present invention will be described.
[0097]
FIG. 14 is a flowchart illustrating an operation procedure of a reduced layout process of the control device 220 according to the second embodiment of the present invention. The following is the sequence of outputting one sheet of paper. In the first embodiment, the quantization matrix is switched on a page basis, but in the present embodiment, the quantization matrix is switched on a tile basis.
[0098]
First, the control device 220 searches a management table for managing information for each page when storing the compressed image data having the concept shown in FIG. 5 on the hard disk. Then, among the read pages arranged on the output sheet, a quantization matrix with the highest compression rate used at the time of scanning is obtained (step S1401). Here, if the quantization matrix having the highest compression ratio is T4, all read pages to be arranged on the output paper are adjusted to the image quality compressed at T4 by the following sequence. However, if all the read pages have been compressed at T1, there is no need to perform recompression.
[0099]
Next, the control device 220 sets, in the color image encoder 107, the quantization matrix having the highest compression rate among the read pages to be arranged on the output sheet searched by the above-described procedure (step S1402). After that, the control device 220 prepares to sequentially read the image data of the read page to be arranged on the output sheet from the hard disk 109 in tile units (step S1403). Specifically, the quantization matrix of the next tile is obtained by referring to the management table and the header information of each tile based on the layout on the paper.
[0100]
Then, based on the obtained quantization matrix, it is determined whether or not the tile needs to be recompressed (step S1404). As a result, if the obtained quantization matrix is not the one with the highest compression rate among the read pages arranged on the output paper, recompression processing is necessary (Yes), and the recompression processing is performed. Become. That is, the selectors 112 and 102 are set, and the image data is recompressed by the quantization matrix having the highest compression ratio among the read pages to be arranged on the output paper through the recompression path shown in FIG. This is performed (step S1405).
[0101]
If the obtained quantization matrix has the highest compression rate among the read pages arranged on the output sheet, it is not necessary to perform the recompression process (No). (Step S1406). At the time of printout, both the normal image data and the recompressed image data are converted by the color image decoder 111 into the inverse quantization matrix having the highest compression ratio among the read pages arranged on the output sheet. Decrypted.
[0102]
Furthermore, it is determined whether or not the read tile is the last tile among the read pages to be arranged on the output sheet (step S1407). If the tile is not the last tile (No), the process returns to step S1403. On the other hand, if it is the last tile (Yes), the print output ends.
[0103]
That is, the present invention relates to image input means for inputting image data composed of a plurality of pages compression-encoded at a predetermined compression ratio, and a compression condition when each page of the input image data is compression-encoded. Information extracting means for extracting information, decoding means for decoding the compression-encoded image data based on the compression condition, and the highest compression ratio in the extracted compression condition. And re-encoding means for performing compression-encoding under the compression condition according to (1), and output means for outputting compression-encoded image data.
[0104]
<Third embodiment>
The present invention is not limited to the first and second embodiments. For example, it will be described below that the effects of the present invention can be utilized even in a function generally called an enlarged layout.
[0105]
FIG. 15 is a schematic diagram for explaining an enlarged layout function according to the third embodiment of the present invention. Note that the enlarged layout is a function of dividing and reading one original, enlarging each of the divided originals, and outputting the enlarged original on a plurality of sheets. For example, in the case shown in FIG. 15, one read original is divided into four and read, each is enlarged by 200%, and output on four sheets. As a result, the user can paste the output sheet with a glue or the like into one large sheet, and obtain a copy output for a large output sheet that cannot be passed through a copying machine.
[0106]
At this time, if each of the divided and read images is compressed by using a different quantization matrix, the image quality differs depending on a portion on a large output sheet created by a user later. Therefore, in the present invention, the image quality of each image on paper is made uniform by performing recompression processing for each image used for the enlarged layout. In the case of the example shown in FIG. 15, one document is divided into four and the reading operation is performed as four documents. Therefore, the recompression sequence is the same as the procedure shown in the first embodiment.
[0107]
That is, the present invention provides image input means for inputting image data of one page which has been compression-encoded, decoding means for decoding the input image data, and decoding of the decoded image data into a plurality of images of a predetermined size. Dividing means for dividing the image data decoded under the same condition for each divided area at a predetermined enlargement ratio, and an output means for outputting the enlarged image data. It is characterized by.
[0108]
Further, the present invention is characterized in that the enlargement means enlarges the enlarged divided image data at an enlargement ratio that is the same as the image size of the input image data.
[0109]
Note that the present invention is applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), but a device including one device (for example, a copying machine, a facsimile machine, etc.). May be applied.
[0110]
Further, an object of the present invention is to supply a recording medium (or a storage medium) recording a program code of software for realizing the functions of the above-described embodiments to a system or an apparatus, and to provide a computer (or a CPU or a CPU) of the system or the apparatus. Needless to say, the present invention can also be achieved by the MPU) reading and executing the program code stored in the recording medium. In this case, the program code itself read from the recording medium implements the functions of the above-described embodiment, and the recording medium on which the program code is recorded constitutes the present invention. When the computer executes the readout program code, not only the functions of the above-described embodiments are realized, but also an operating system (OS) running on the computer based on the instruction of the program code. It goes without saying that a part or all of the actual processing is performed and the functions of the above-described embodiments are realized by the processing.
[0111]
Further, after the program code read from the recording medium is written into a memory provided in a function expansion card inserted into the computer or a function expansion unit connected to the computer, the function is executed based on the instruction of the program code. It goes without saying that the CPU included in the expansion card or the function expansion unit performs part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.
[0112]
When the present invention is applied to the recording medium, the recording medium stores program codes corresponding to the flowcharts described above.
[0113]
【The invention's effect】
As described above, according to the present invention, when a job for compressing image data composed of a plurality of pages is given, deterioration of the image quality of each page is minimized as much as possible, and at the time of output, each area of the page is output. Image quality can be uniformed.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of an image processing apparatus according to an embodiment of the present invention.
FIG. 2 is a schematic diagram illustrating a processing procedure of a color image encoder 103 and a color image decoder 104 using DCT according to an embodiment of the present invention.
FIG. 3 is a diagram illustrating an example of an 8 × 8 quantization matrix used for compression processing according to the embodiment.
FIG. 4 is a schematic diagram illustrating a data structure of compressed image data according to the embodiment.
FIG. 5 is a conceptual diagram of a management table for managing information of each page of compressed image data in the embodiment.
FIG. 6 is a schematic diagram for explaining tiles of image data to be compressed in the embodiment.
FIG. 7 is a flowchart illustrating an image reading process performed by a control device 220 according to the present embodiment.
FIG. 8 is a flowchart illustrating details of a rescan process in the control device 220 according to the present embodiment.
FIG. 9 is a diagram showing communication timings of an image reading processing sequence among the control device 220, the document feeding unit 250, and the scanner unit 210 in the embodiment.
FIG. 10 is a diagram illustrating communication timings of an image reading processing sequence in which a re-scanning process occurs between the control device 220, the document feeding unit 250, and the scanner unit 210 according to the embodiment.
FIG. 11 is a block diagram illustrating an image encoding unit and an image decoding unit in a print sequence according to an embodiment of the present invention.
FIG. 12 is a flowchart illustrating an operation procedure of an image reading process of the control device 220 in a print sequence.
FIG. 13 is a schematic diagram for explaining a reduced layout function according to the second embodiment of the present invention.
FIG. 14 is a flowchart illustrating an operation procedure of a reduced layout process of the control device 220 according to the second embodiment of the present invention.
FIG. 15 is a schematic diagram for explaining an enlarged layout function according to the third embodiment of the present invention.
FIG. 16 is a schematic diagram for explaining a configuration of a conventional image processing apparatus provided with an image memory.
FIG. 17 is a diagram illustrating communication timing of an image reading processing sequence between a control device, a sheet feeding unit, and a scanner unit in a conventional image processing apparatus.
FIG. 18 is a diagram showing a communication timing of an image reading process sequence between a control device, a sheet feeding unit, and a scanner unit in a conventional image processing apparatus that performs a rescan process.
[Explanation of symbols]
100, 102, 112 selector
101 Block line buffer for compression
103, 107 color image encoder
104,111 color image decoder
105, 115 Block line buffer for expansion
106, 110 Compressed memory buffer
109 Hard Disk (HDD)
120 code amount determination unit
121 Page Description Language Rendering Unit
200 Leader Club
210 Scanner unit
220 control device
250 Document feeding unit
310 Printer section

Claims (1)

A document reading means for reading a document and generating image data for one page; and a second compression unit which compresses image data sequentially generated by the reading unit for each page under a first compression condition or a higher compression ratio. A control method of an image processing apparatus, comprising: an encoding unit capable of performing compression encoding under a condition; and a storage unit configured to store compression-encoded image data.
It is obtained when all the pages are compression-encoded under the first compression condition while the image data for one page generated by the reading unit is being compression-encoded under the first compression condition. An estimation step of estimating the encoded data amount for one page;
If the estimated coded data amount is equal to or smaller than the target value, a decision is made to issue an instruction to read the next original to the reading means in order to generate image data to be compressed and coded next during the compression coding. If the estimated encoded data amount is equal to or larger than the target value, it is determined that an instruction to read the original corresponding to the image data in the middle of encoding is read again during the compression encoding. A decision step;
When the estimated encoded data amount is equal to or larger than the target value, a re-encoding step of compression-encoding the image data generated by reading the original again by the reading means under the second compression condition. A method for controlling an image processing apparatus, comprising:

Images