JP2004032434A - Image processing apparatus and control method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processing apparatus capable of efficiently compressing image data into a data amount not greater than a desired data amount by reducing unnecessary repetitions of re-scanning as much as possible, and to provide a control method thereof. <P>SOLUTION: Image data are inputted from a reader unit 2. The input image data are compressed in a color image encoder 9 in a control unit 3. In this case, during compressing the image data, the data amount of the image data after being compressed is estimated. If the data cannot be compressed into a data amount not greater than a prescribed data amount, the unit 2 is made to re-input the image data. On the other hand, a compression rate at the time of re-compressing the image data to be re-inputted is determined on the basis of the compression state of the image data. The re-input image data are re-compressed by using the determined compression rate. The image data compressed in this way are stored in a hard disk 11. Also, the image data decoded by a color decoder 13 are outputted from a printer unit 4. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image processing apparatus for suitably compressing image data to a predetermined data amount or less and a control method thereof.
[0002]
[Prior art]
Conventionally, when handling color image data, the size of the data has been a problem. For example, when a binary image that can be expressed as a black and white image is expressed as a standard color image composed of 8 bits for each of RGB, a data amount that is 24 times as large as the same size (size) is required. That is, compared to the case where the black-and-white image data is stored in a storage device such as a hard disk or a memory, storing the same number of color image data requires a storage capacity 24 times that of the black-and-white image data.
[0003]
As described above, when color image data is handled in a computer, a memory capacity and a hard disk capacity that are 24 times larger than when a monochrome image is handled are required. This leads to a large cost increase. Therefore, when color image data is handled, usually, a compression process is performed to reduce the amount of data to be handled, thereby reducing a memory capacity and a hard disk capacity mounted on various devices and suppressing a cost increase. ing.
[0004]
The configuration of a general color copying machine to which the above technique is applied will be described. FIG. 10 is a block diagram showing the configuration of the overall configuration of a conventional color copying machine having an image memory. As shown in FIG. 10, the color copying machine mainly includes a reader unit 102, a printer unit 109, and a control device 101. The reader unit 9 includes a document feeding unit 107 having a function of conveying a document sheet, and a scanner unit 108 having a function of reading a document.
[0005]
The control device 8 controls the document feed unit 107 and the scanner unit 108 of the reader unit 102 to read the image data of the document, and controls the printer unit 109 to output the image data to the recording paper and perform a copy function. I will provide a. The control device 101 includes a memory 105 for storing image data, an encoding unit 104 for compressing data before storing the image data in the memory 105, and a decoding unit 103 for decoding compressed image data.
[0006]
FIG. 11 is a sequence diagram for explaining control timings of the control device 101, the document feeding unit 107, and the scanner unit 108. Communication between the units is performed by a known technique such as command transmission by serial communication.
[0007]
First, a copy operation start request command is given to the control device 8 from an operation unit (not shown) (step S201). As a result, the control device 101 issues a document feed request command to the document feed unit 107 (step S202). In response, the document feeding unit 107 performs a sheet feeding operation (step S203), and when the sheet feeding operation is completed, issues a sheet feeding completion command to the control device 101 (step S204).
[0008]
In response, the control device 101 issues a scan start request command to the scanner unit 108 (step S205). The scanner unit 108 issues a scan preparation completion command in response to the scan start request command (step S206). Thereafter, the scanner unit 108 starts a scanning operation (step S207), reads the document, and transfers the image data to the control device 101 (step S208). When the scanning operation is completed and the image transfer is completed, the scanner unit 108 issues a scanning operation completion command to the control device 101 and the document feeding unit 107 (steps S209 and S210).
[0009]
The control device 101 that has received the scan operation completion command indicating the end of the image data transfer issues a feed request command for the second document to the document feed unit 107 (step S211). Upon receiving the scan request command for the second document, the document feed unit 107 receives the scan operation completion command and performs an operation of discharging the first document and simultaneously feeding the second document. Can be performed (step S212). After the completion of the document exchange operation, the document feeding unit 107 issues a command for completing the feeding of the second document to the control device 101 (step S213).
[0010]
Further, the control device 101 receives a feed completion command for the second document, and issues a scan start request command to the scanner unit 108 (step S214). In the subsequent sequence, the above sequence is repeated for the number of originals.
[0011]
FIG. 11 is a sequence diagram for explaining control timings of the control device 101, the document feeding unit 107, and the scanner unit 108 when there are only two documents set in the document feeding unit 107. Accordingly, in the example shown in FIG. 11, in response to a paper feed request for the third document (step S220), the document feed unit 107 performs a sheet discharging operation for the second document (step S221). Then, a document end notification is issued to the control device 8 (step S222), and the document reading operation ends.
[0012]
[Problems to be solved by the invention]
However, when a variable-length compression method such as JPEG compression is used as a compression processing method in the encoding unit 104 in FIG. 10 that can suppress a rise in cost with a higher compression rate, the compression is performed until image compression processing is actually performed. The data amount of the processed image data is not determined. Therefore, when the image data is actually read and the compression process is performed, a problem may occur that the data is not compressed to a data amount desired by the user or less.
[0013]
FIG. 12 illustrates control timings of the control device 101, the document feeding unit 107, and the scanner unit 108 when rescanning the image data after the image data size is determined by performing the compression processing of the image data. FIG. As shown in FIG. 12, the control device 101 waits for the end of the image transfer from the scanner unit 108 (step S301). Then, after the size of the image data is determined, if the size exceeds the desired size, the control device 101 changes the setting of the encoding unit 104 to compress the image at a higher compression rate. Then, instead of issuing a feed request command for the next original, a scan start request command is issued again (step S302).
[0014]
As described above, in the conventional color copying machine, the image is read again from the same document. As a matter of course, the conventional color copying machine has a problem in that the productivity of copying is deteriorated by the time required for rescanning. Further, the example shown in FIG. 12 is a case where rescanning is performed once. However, if the target image data is a complex image or the like and an image having a low compression ratio, rescanning is repeated a plurality of times. In addition, there arises a problem that the productivity of copying is further reduced.
[0015]
The present invention has been made in view of such circumstances, and an image processing apparatus and an image processing apparatus capable of efficiently reducing image data to a desired data amount or less by minimizing redundant rescanning as much as possible. It is an object to provide a control method.
[0016]
[Means for Solving the Problems]
In order to solve the above problem, the present invention provides an image processing apparatus comprising: an image input unit that inputs image data; a compression unit that compresses the input image data; and an image output unit that outputs the compressed image data. An apparatus, wherein during the compression of the image data by the compression unit, an estimation unit for estimating a data amount of the compressed image data, and when it is estimated that the image data is not compressed to a predetermined data amount or less, Re-input control means for re-inputting the image data to the image input means, and compression rate determining means for determining a compression rate when re-compressing the re-input image data based on the compression state of the image data. The image processing apparatus further includes a compression unit that recompresses the re-input image data using the determined compression ratio.
[0017]
Further, the image processing apparatus according to the present invention further includes a data amount accumulating means for accumulating and adding a data amount of the image data when the image data is compressed for each predetermined region, and wherein the estimating means includes It is characterized by estimating whether or not the image data can be compressed to a predetermined data amount or less based on the data amount and the number of compressed areas.
[0018]
Further, in the image processing apparatus according to the present invention, the compression unit enables the compression of the image data by a plurality of compression ratios, and the compression ratio determination unit determines the compression ratio during the compression processing of the image data and the plurality of compression ratios. The compression ratio when re-compressing the image data is determined on the basis of the compression ratio and the accumulated data amount.
[0019]
Still further, the image processing apparatus according to the present invention further comprises a setting unit for setting a timing for executing the re-input and re-compression of the image data, and the re-input control unit and the compression ratio determining unit based on the set timing. And a control unit for executing a predetermined processing operation on the control unit.
[0020]
Still further, in the image processing apparatus according to the present invention, the image input unit is a PDL controller.
[0021]
Furthermore, an image processing apparatus according to the present invention is characterized in that the image input means is an optical reading device.
[0022]
Still further, the image processing apparatus according to the present invention is characterized in that the compression means compresses the image data using a JPEG compression method.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an image processing apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings.
[0024]
<First embodiment>
FIG. 1 is a block diagram illustrating a configuration of an image processing apparatus including an image data input unit, a storage unit, and an output unit. As shown in FIG. 1, the image processing apparatus according to the present embodiment includes a page description language (PDL) rendering unit 1, a reader unit 2, a control device 3, and a printer unit 4.
[0025]
In FIG. 1, a page description rendering unit 1 and a reader unit 2 correspond to an input unit for image data to be compressed. The reader unit 2 includes a document feeding unit 5 having a function of transporting a document sheet and a scanner unit 6 having a function of reading a document.
[0026]
The control device 3 controls the document feed unit 5 and the scanner unit 6 of the reader unit 2 to read the image data of the document and controls the printer unit 4 to form the image data on recording paper or the like. Provides a copy function.
[0027]
As shown in FIG. 1, the control device 3 includes a selector 7 for switching an image input system (image input from the page description language rendering unit 1 or the reader unit 2), a compression block line buffer 8, a color image encoder 9, It comprises a compression buffer 10, a hard disk (HDD) 11, a compression buffer 12, a color image decoder 13, and a development block line buffer 14.
[0028]
In the present embodiment, signals from the input unit include input signals from the scanner unit 6 and the page description language rendering unit 1. When the image processing apparatus according to the present embodiment is used as a copying machine, the selector 7 is switched, so that the scanner unit 6 is used. When the image processing apparatus is used as a printer, it is input from the page description language rendering unit 1. The selector 7 is switched accordingly.
[0029]
The compressed block line buffer 8 divides the image switched and input by the selector 7 into tiles of M × N (pixels). This division is performed for processing in the color image encoder 9 connected to the compressed block line buffer 8. That is, the color image encoder 9 performs compression encoding of image data by the JPEG compression method. Therefore, in the color image encoder 9, since the discrete cosine transform is performed on the tiles of M × N (pixels), M and N are multiples of the window size for the discrete cosine transform.
[0030]
For example, in JPEG compression used in the color image encoder 9, if the window size for compression is 8 × 8 (pixels) and M = N = 32, 32 × 32 (pixels) tiles are further added to 16 tiles. The image is divided into 8 × 8 (pixel) areas, and JPEG compression is performed in units of 8 × 8 (pixels). In this embodiment, M = N = 32 will be described, but the present invention is not limited to this value.
[0031]
The color image encoder 9 performs a well-known DCT transform on the 16 8 × 8 (pixel) windows included in the 32 × 32 pixel tile image, and then performs quantization. In the present embodiment, 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. The switching of the quantization matrix in the present embodiment is performed by a CPU (not shown) which generates a selection signal for selecting a plurality of quantization matrices held in the color image encoder 9 in advance and sends the selection signal to the color image encoder 9. By sending it.
[0032]
The image data encoded by the color image encoder 9 is stored in a hard disk (HDD) 11 as compressed image data via a compression buffer 10.
[0033]
Next, when outputting the compressed image stored in the hard disk 11 from the printer unit 4, the compressed image data stored in the hard disk 11 is read, and the color image decoder 13 decodes and outputs the compressed image data in the following procedure. I do.
[0034]
First, in accordance with the quantization matrix at the time of compressing the image, the decoding parameter of the compressed and stored image data (hereinafter, referred to as “inverse quantization matrix”) is switched to decode the image data. The result is output to the development block line buffer 14.
[0035]
That is, the image processing apparatus according to the present invention includes image input means for inputting image data, a color image encoder 9 for compressing input image data, and image output means for outputting compressed image data. These are controlled by the control device 3. Then, the control device 3 estimates the data amount of the compressed image data during the compression of the image data by the color image encoder 9, and when it is estimated that the image data is not compressed to a predetermined data amount or less, The input means re-inputs the image data, determines a compression ratio when re-compressing the re-input image data based on the compression state of the image data, and uses the determined compression ratio to perform color image coding. The image data re-input to the device 9 is re-compressed.
[0036]
Further, the present invention is characterized in that the image input means is the scanner unit 6. Further, the present invention is characterized in that the color image encoder 9 compresses image data using a JPEG compression method.
[0037]
FIG. 2 is a block diagram illustrating a detailed configuration when the control device 3 is viewed as an encoding processing unit and a decoding processing unit that execute encoding processing and decoding processing of image data. In FIG. 2, reference numeral 200 denotes an image signal input from an image input device (not shown). In the case of a color signal, 256 colors of red (R), green (G), and blue (B) are used. It is a key signal. The image signal 200 is input to the color converter 21 and converts the RGB signals into luminance and color difference signals (YCbCr). Next, the discrete cosine transform (DCT) unit 22 performs spatial frequency transform (DCT transform) on each of the luminance and color difference signals in units of 8 × 8 (pixels).
[0038]
Further, the quantizer 23 quantizes the DCT coefficients using the set quantization matrix, thereby reducing the data amount. Then, in the variable length coder (VLC) unit 24, the reduced quantized value is further reduced by Huffman coding processing. The above is the configuration of the encoding processing unit and the operation of each unit. The compressed image data is stored in the storage device 25 such as a compression memory or a large-capacity storage device.
[0039]
Next, the stored data is decoded in the following procedure. First, Huffman decoding is performed on the compressed image data by a variable length decoder (VLD) 26. Next, in the inverse quantizer 27, the DCT coefficient value is returned to a DCT coefficient value by a preset inverse quantization matrix. Further, the inverse DCT transform is performed by the IDCT unit 28 to return to the luminance / color difference signal. Further, the luminance / color difference signal is returned to the RGB signal by the color converter 29. Thus, a color image signal 201 output to the outside is obtained.
[0040]
FIG. 3 is a diagram illustrating an example of a quantization matrix for 8 × 8 DCT coefficients used in the present embodiment. 3A shows an example of the quantization matrix T1 applied first, and FIG. 3B shows an example of the quantization matrices T2, T3, T4... Applied to increase the compression ratio. I have.
[0041]
In the present embodiment, first, compression encoding is performed using the quantization matrix T1, and if image data cannot be compressed to a desired data amount or less, a matrix for coarsening the quantization step, for example, quantization matrices T2, T3, T4 The compression is performed using any one of. Here, which one of the quantization matrices T2, T3, T4,... Is selected depends on the compression state of the quantization matrix T1. Details of this processing will be described later.
[0042]
As described above, in the present embodiment, the quantization matrices T1, T2, T3, T4... And the corresponding inverse quantization matrices are stored in the quantizer 23 and the inverse quantizer 27 shown in FIG. It is assumed that which is to be used is switched by a CPU (not shown) in accordance with the quantization matrix at the time of compressing the image data.
[0043]
FIG. 4 is a conceptual diagram showing a data structure when the compressed image data is stored in the compression block line buffer 8 and the hard disk 11. As shown in FIG. 4, header information 41 of the first tile and DCT-encoded image information 42 are stored in order from the top of the image data, and information on the second tile and information on the third tile have the same configuration. Data is continuously written as information. In this way, information up to the last tile included in one entire page is written.
[0044]
The header information of each tile records the data size of the compressed data, the number of the tile, and the like. At the same time, information as to whether the quantization matrix T1 is used or the quantization matrices T2, T3, T4,.
[0045]
Therefore, when decoding the encoded and recorded image data, the information of whether the used quantization matrix is T1, T2, T3, T4,... The inverse quantization may be performed by selecting the inverse quantization matrix.
[0046]
That is, in the image processing device according to the present invention, the color image encoder 9 enables compression of image data at a plurality of compression ratios. Then, the image processing apparatus determines a compression rate when re-compressing the image data based on the compression rate during the compression processing of the image data, the plurality of compression rates, and the data amount that is cumulatively added. I do.
[0047]
In the present embodiment, as described above, image data is divided into tiles of 32 (pixel) × 32 (line) units, 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 even by a compression method such as JPEG compression that is originally performed using an image for one page. . This makes it possible to estimate the compressed image size of the entire page by estimating the size of the remaining image data of the page.
[0048]
According to the equation (1), the size of the image data for one page, the target compression ratio, the number of tiles of the entire image, and the A predetermined number of tiles for estimating the image size of one page, and the relationship between the image data size at the predetermined number of tiles can be represented.
[0049]
Sn · Pt> α · (1-x / X) + x · Sc / X (1)
In equation (1), Sn is the size of image data for one page when not compressed, Pt is a target compression ratio (1.0 is not compressed at all), and α is a part that has not been read yet. X is a predetermined number of tiles for estimating the image size after compression, X is a number of tiles for one page of image data, and Sc is a predetermined number of tiles (x). It shows the cumulative value of the size of the image data at the point in time.
[0050]
FIG. 5 is a schematic diagram for explaining image data in which one page includes 14 tiles in the main scanning direction and 10 tiles in the sub-scanning direction. At the time when up to the tiled portion (126 pieces) indicated by hatching in the image data for one page shown in FIG. 5, the following values are applied as the parameters of the equation (1). Can be. For simplicity of explanation, it is assumed that the image of one tile is 1 (MB) when not compressed, and that the image data of the part that has not been read is not compressed at all even if the encoding process is performed. Is calculated.
[0051]
That is, Sn = 140 (MB), Pt = 1/8, α = 1.0 (that is, image data of a part that has not been read is not compressed at all), x = 126, X = 140, Sc <3.89 (MB).
[0052]
That is, in this example, the cumulative value of the size of the image data must be smaller than 3.89 (MB) until the 126th tile is read out of the 140 tiles of the image data for one page. If the cumulative value is larger than 3.89 (MB), rescanning is performed.
[0053]
That is, the image processing apparatus according to the present invention cumulatively adds the data amount of the image data when the image data is compressed for each predetermined region, and based on the cumulatively added data amount and the number of compressed regions, Is estimated to be able to be compressed to a predetermined data amount or less.
[0054]
Further, the image processing device according to the present invention enables the color image encoder 9 to compress image data at a plurality of compression ratios. Then, the image processing apparatus determines a compression rate when re-compressing the image data based on the compression rate during the compression processing of the image data, the plurality of compression rates, and the data amount that is cumulatively added. I do.
[0055]
FIG. 6 is a flowchart for explaining an image reading control procedure in the scan sequence of the control device 3 of the image processing apparatus according to the present embodiment. First, the control device 3 is in a reading operation start request waiting state (step S1701). Upon receiving a reading operation start request from an operation unit (not shown), the control device 3 issues a first document feed request command to the document feed unit 5 (step S1702).
[0056]
Thereafter, the control device 3 is in a state of waiting for a paper-feed completion notification from the document feed unit 5 (step S1703). Then, upon receiving a feed completion notification from the document feed unit 5, the control device 3 issues a scan start request to receive image data, performs encoding processing for each tile image, compresses the tile image, and outputs the next document. Is read or the same document is scanned again with the quantization matrix changed (step S1704). Details of this processing will be described later.
[0057]
After that, the control device 3 waits for a scan completion notification from the scanner unit 6 indicating the end of the transfer of the image data (step S1705). If the last document read immediately before is the last one, the reading operation is terminated. If there is still a document to be read remaining in the document feeding unit 5, the control device 3 issues a notification of completion of feeding the next document. The state shifts to a waiting state (step S1706).
[0058]
FIG. 7 is a flowchart for explaining a control procedure in the re-scanning process and the compression process of the control device 3.
[0059]
First, before receiving the image data, the control device 3 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 S1501). Next, the control device 3 determines whether or not the next scan operation is a rescan by referring to the value of a counter that counts the number of rescans (step S1502). As a result, if it is a rescan (Yes), it is checked whether the number of rescans is equal to or less than a predetermined number (step S1503). On the other hand, if it is not a re-scan (No), the process proceeds to step S1505.
[0060]
If the result of the check in step S1503 is that the number of rescans is greater than the predetermined number (No), the reading operation is terminated as an error. On the other hand, if the number is equal to or less than the predetermined number (Yes), the quantization matrix is determined according to the compression state of the previous scan (step S1504). For example, in the first reading scan, if the cumulative value Sc of the image data size exceeds 3.89 (MB) in the 126th tile described above, the achievable compression ratio is predicted by performing an inverse calculation.
[0061]
For example, if it is possible to compress up to the 126th tile out of 140, the compression ratio may be increased a little more, and the above-described T2 quantization matrix is selected. Further, if the image data size becomes insufficient for the 50th tile, for example, it is necessary to greatly increase the size of the image data, and a T3 or T4 quantization matrix with higher compression is selected. The predetermined number of tiles for estimating the compression ratio, the predetermined size of the image data at the number of tiles, and the like are also determined according to the quantization matrix.
[0062]
On the other hand, 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 also set to the initial value (step S1505). Further, a predetermined number of tiles for estimating a compression ratio and a predetermined size of image data at the number of tiles are determined according to the quantization matrix.
[0063]
After the processing in steps S1504 and S1505, preparation for receiving the image data is ready, so the control device 3 issues a scan start request command to the scanner unit 6 (step S1506). After that, the control device 3 enters a state of waiting for a notification of completion of scan preparation from the scanner unit 6 (step S1507).
[0064]
Upon receiving the scan preparation completion notification, the control device 3 enters a state of waiting for tile image reception (step S1508). When the tile image is received, the control device 3 adds the size of the received tile image after performing the encoding process and compressing it to a counter for accumulating the size of the image data (step S1509). Also, one counter for counting the number of received tiles is added (step S1510).
[0065]
Next, it is determined whether or not the value of the image data size cumulative value counter exceeds a predetermined size (step S1511). As a result, if it exceeds (Yes), the control device 3 adds a counter for counting the number of rescans (step S1512), and waits for a scan completion notification (step S1513).
[0066]
As a result, when a scan completion notification is received (Yes), the process shifts to a rescan sequence. In this case, since the image reading scan is performed without issuing the next document feed request command to the document feeding unit 5, the image reading scan is performed on the same document as the previously read document, that is, A rescan will be performed.
[0067]
On the other hand, if it is determined in step S1511 that the number does not exceed (No), it is next checked whether the number of received tiles does not exceed a predetermined number (step S1514). As a result, if not exceeded (No), the control device 3 shifts to a tile image reception waiting state. On the other hand, if the number of tiles exceeds the predetermined number (Yes), the control device 3 determines that the cumulative size of the image data is equal to or smaller than the predetermined size even if the predetermined number of tiles are received. It is estimated that the image data of the page will be smaller than a certain size, and a command for requesting the next document feed is issued to the document feed unit (step S1515).
[0068]
As described above, instead of sequentially increasing the compression ratio of the quantization matrix to T1, T2, T3, T4,... Each time the compression ratio has not been reached, T2, T3, T4 is determined based on the previous compression ratio. ... Since one of the quantization matrices is selected, the number of unnecessary rescans can be reduced.
[0069]
FIGS. 8 and 9 are diagrams showing an operation sequence between the document feeding unit 5 and the scanner unit 6 by the control device 3 when no rescan occurs and when a rescan occurs, respectively.
[0070]
Hereinafter, the control timing of the document feed unit 5 and the scanner unit 6 by the control device 3 will be described with reference to FIG. Communication between the units is performed by a known technique such as command transmission by serial communication.
[0071]
First, a copy operation start request command is given from the operation unit (not shown) to the control device 3 (step S801). As a result, the control device 3 issues a document feed request command to the document feed unit 5 (step S802. In response, the document feed unit 5 performs a sheet feeding operation (step S803). When the operation is completed, a paper feed completion command is issued to the control device 3 (step S804).
[0072]
In response, the control device 3 issues a scan start request command to the scanner unit 6 (step S805). After issuing a scan preparation completion command in response to the scan start request command (step S806), the scanner unit 6 starts a scanning operation (step S807), reads a document, and transfers image data to the control device (step S807). S808).
[0073]
If the accumulated size of the image data is equal to or smaller than the predetermined size at the time when the image of the predetermined number of tiles is received during the reception of the image data, the control device 3 sends the second document to the document feeding unit 5. Is issued (step S809).
[0074]
When the scanning operation is completed and the image transfer is completed, the scanner unit 5 issues a scanning operation completion command to the control device 3 and the document feeding unit 5 (steps S810 and S811).
[0075]
The document feeding unit 5, 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 S812). After the document exchange operation is completed, the document feeding unit 5 issues a command for completing the feeding of the second document to the control device 3 (step S813).
[0076]
The control device 3, which has received the scan operation completion command for the first document in advance, issues a scan start request command to the scanner unit 6 in response to the feed completion command for the second document (step S814). ). Hereinafter, the above-described sequence is repeated for the number of originals.
[0077]
In the example shown in FIG. 8, it is assumed that there are only two originals set in the original feeding unit 5, and therefore, in response to a feed request for the third original, the original feeding unit 5 performs a sheet discharging operation for the second document (step S815), thereafter issues a document end notification to the control device 3 (step S816), and ends the reading operation.
[0078]
Next, the control timing of the control unit 3 with the document feeding unit 5 and the scanner unit 6 when rescanning occurs will be described with reference to FIG.
[0079]
First, a copy operation start request command is given from the operation unit (not shown) to the control device 3 (step S901). As a result, the control device 3 issues a document feed request command to the document feed unit 5 (step S902). Then, in response to this, the document feeding unit 5 performs a sheet feeding operation (step S903), and when the sheet feeding operation is completed, issues a sheet feeding completion command to the control device 3 (step S904).
[0080]
In response, the control device 3 issues a scan start request command to the scanner unit 6 (step S905). Then, in response to the scan start request command, the scanner unit 6 issues a scan preparation completion command (step S906), starts a scanning operation (step S907), reads a document, and transfers image data to the control device. (Step S908).
[0081]
Here, 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 3 sends the second sheet to the document feeding unit 5. Without issuing a feed request command for the document, the scanner enters a scan operation completion command reception wait state.
[0082]
Then, when the scanning operation is completed and the image transfer is completed, a scanning operation completion command is issued to the control device 3 and the document feeding unit 5 (steps S909 and S910). In response to this, the control device 3 issues a scan start request command to the scanner unit 6 (step S911). Here, since the feed request command for the second document has not been issued, the document feed unit 5 has not fed the next document, and as a result, scans the first document again. Will be read. The following is the same as the sequence shown in FIG.
[0083]
<Other embodiments>
Further, in the above-described embodiment, the case where the input source of the image data is the reader unit 2 has been described. However, even when the input source is the page description language rendering unit 1 in FIG. It is possible to do. That is, the image processing apparatus according to the present invention is characterized in that the image input means is a PDL controller.
[0084]
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.
[0085]
Further, an object of the present invention is to supply a recording medium (or a recording medium) in which a program code of software for realizing the functions of the above-described embodiments is recorded to a system or an apparatus, and 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.
[0086]
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 expansion is performed based on the instruction of the program code. It goes without saying that the CPU or the like provided in the 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.
[0087]
When the present invention is applied to the recording medium, the recording medium stores program codes corresponding to the flowcharts described above.
[0088]
As described above, according to the present invention, at the time of recompression, the code amount control is performed by determining the target compression rate based on the compression state at the time of the previous compression, so that unnecessary rescanning can be minimized. In addition, it is possible to achieve a desired compression ratio while minimizing deterioration of the productivity of the device. Further, according to the present invention, it is possible to form an image of as high quality as possible while performing compression with a more appropriate compression control parameter according to an image to prevent a decrease in performance.
[0089]
【The invention's effect】
As described above, according to the present invention, image data can be efficiently compressed to a desired data amount or less by minimizing unnecessary rescanning.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of an image processing apparatus including an input unit, an accumulation unit, and an output unit for image data.
FIG. 2 is a block diagram illustrating a detailed configuration when the control device 3 is viewed as an encoding processing unit and a decoding processing unit that execute encoding processing and decoding processing of image data.
FIG. 3 is a diagram illustrating an example of a quantization matrix for 8 × 8 DCT coefficients used in the present embodiment.
FIG. 4 is a conceptual diagram showing a data structure when compressed image data is stored in a compression block line buffer 8 and a hard disk 11.
FIG. 5 is a schematic diagram for explaining image data in which one page includes 14 tiles in the main scanning direction and 10 tiles in the sub-scanning direction.
FIG. 6 is a flowchart for explaining an image reading control procedure in a scan sequence of the control device 3 of the image processing apparatus according to the present embodiment.
FIG. 7 is a flowchart illustrating a control procedure in a rescan process and a compression process performed by the control device 3.
FIG. 8 is a diagram showing an operation sequence between the document feeding unit 5 and the scanner unit 6 by the control device 3 when re-scanning does not occur.
FIG. 9 is a diagram showing an operation sequence between the document feeding unit 5 and the scanner unit 6 by the control device 3 when a rescan occurs.
FIG. 10 is a block diagram showing an overall configuration of a conventional color copying machine provided with an image memory.
FIG. 11 is a sequence diagram for explaining control timings of a control device 101, a document feeding unit 107, and a scanner unit 108.
12 illustrates control timings of the control device 101, the document feed unit 107, and the scanner unit 108 when rescanning image data after image data compression processing is performed to determine the image data size. FIG. FIG.
[Explanation of symbols]
1 Page description language rendering unit
2 Leader Club
3 control device
4 Printer section
5 Document feeding unit
6 Scanner unit
7 Selector
8 Block line buffer for compression
9 Color image encoder
11 Hard Disk
13 Color image decoder
14 Block line buffer for expansion

Claims (16)

An image processing apparatus comprising: image input means for inputting image data, compression means for compressing input image data, and image output means for outputting compressed image data,
Estimating means for estimating the data amount of the compressed image data during the compression of the image data by the compression means,
When it is estimated that the image data is not compressed to a predetermined data amount or less, re-input control means for re-inputting the image data to the image input means,
A compression ratio determining unit that determines a compression ratio when re-compressing the re-input image data based on the compression state of the image data,
An image processing apparatus, wherein the compression unit re-compresses re-input image data using the determined compression ratio. Data amount accumulating means for accumulating and adding the data amount of the image data when the image data is compressed for each predetermined area,
2. The image processing apparatus according to claim 1, wherein the estimating unit estimates whether or not the image data can be compressed to a predetermined data amount or less based on the cumulatively added data amount and the number of compressed regions. apparatus. The compression means enables compression of the image data by a plurality of compression ratios,
The compression ratio determining means determines a compression ratio when re-compressing the image data based on a compression ratio during compression processing of the image data and the data amount obtained by cumulatively adding the plurality of compression ratios. The image processing apparatus according to claim 2, wherein: Setting means for setting the timing for executing the re-input and re-compression of the image data,
2. The image processing apparatus according to claim 1, further comprising control means for causing said re-input control means and compression ratio determining means to execute predetermined processing operations based on the set timing. The image processing apparatus according to any one of claims 1 to 4, wherein the image input unit is a PDL controller. The image processing apparatus according to any one of claims 1 to 4, wherein the image input unit is an optical reading device. The image processing apparatus according to claim 1, wherein the compression unit compresses the image data using a JPEG compression method. An image input unit for inputting image data, a compression unit for compressing the input image data, and a control method of an image processing apparatus including an image output unit for outputting compressed image data,
An estimating step of estimating a data amount of the compressed image data during the compression of the image data by the compression unit;
When it is estimated that the image data is not compressed to a predetermined data amount or less, a re-input control step of causing the image input means to re-input the image data,
Based on the compression state of the image data, a compression ratio determination step of determining a compression ratio when re-compressing the re-input image data,
A recompression control step of recompressing the image data re-input to the compression means using the determined compression ratio. A data amount accumulating step of accumulatively adding a data amount of the image data when the image data is compressed for each predetermined region,
9. The image processing apparatus according to claim 8, wherein the estimating step estimates whether or not the image data can be compressed to a predetermined data amount or less based on the cumulatively added data amount and the number of compressed regions. How to control the device. A control method of the image processing apparatus, wherein the compression unit enables compression of the image data by a plurality of compression ratios,
The compression ratio determining step determines a compression ratio for recompressing the image data based on a compression ratio during the compression processing of the image data and the data amount obtained by cumulatively adding the plurality of compression ratios. The method for controlling an image processing apparatus according to claim 9, wherein: A setting step of setting a timing for executing the re-input and re-compression of the image data,
9. The control method for an image processing apparatus according to claim 8, further comprising a control step of causing said re-input control means and said compression ratio determining means to execute a predetermined processing operation based on the set timing. . The method according to claim 8, wherein the image input unit is a PDL controller. 12. The method according to claim 8, wherein the image input unit is an optical reading device. 14. The control method according to claim 8, wherein the compression unit compresses the image data using a JPEG compression method. A computer program for controlling an image processing apparatus including image input means for inputting image data, compression means for compressing input image data, and image output means for outputting compressed image data,
An estimating step of estimating a data amount of the compressed image data during the compression of the image data by the compression unit;
When it is estimated that the image data is not compressed to a predetermined data amount or less, a re-input control step of causing the image input means to re-input the image data,
Based on the compression state of the image data, a compression ratio determination step of determining a compression ratio when re-compressing the re-input image data,
A computer program for causing a computer to execute a recompression control step of recompressing image data re-input to the compression unit using the determined compression ratio. A computer-readable recording medium storing the computer program according to claim 15.

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