JP4693309B2 - Image processing apparatus, control method therefor, computer program, and storage medium - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image processing apparatus that compresses and encodes image data, a control method thereof, a computer, and a computer-readable storage medium.
[0002]
[Prior art]
Conventionally, the JPEG method using discrete cosine transform and the method using Wavelet transform are often used as still image compression methods. Since this type of encoding method is a variable length encoding method, the amount of code changes for each image to be encoded.
[0003]
In the JPEG method, which is an international standardization method, only one set of quantization matrices can be defined for an image. Therefore, without pre-scanning, the code amount cannot be adjusted and used in a system that stores in a limited memory. There was a danger of causing memory over.
[0004]
In order to prevent this, in order to adjust the code amount by changing the compression rate and re-reading the original when the code amount exceeds the planned code amount, or by estimating the code amount by pre-scanning in advance , The method of resetting the quantization parameter was taken.
[0005]
On the other hand, the image information includes, in addition to the original image data, image area information accompanying the image data. The image area information is mainly used for color processing and tone adjustment in the image output unit in order to improve the appearance at the time of image output. For natural images with a mixture of chromatic and achromatic colors and black characters often seen in the original, changing the type of ink used in the same black makes the natural image look like a natural image while outputting clear characters I can do it.
[0006]
As described above, each pixel has 1-bit attribute flag data indicating whether it is a chromatic color or an achromatic color and whether it is a character portion, thereby improving the image quality of the output image at the time of image output, particularly at the time of printout. I can do it. The image area information includes information other than the above.
[0007]
In order to compress image information, it is necessary to compress not only the image data but also the image area information. Image area information is a collection of binary data, and in order to compress it, it is basically necessary to use a reversible encoding method. Conventionally, Packbits and JBIG encoding methods have been used for compression of image area information.
[0008]
However, only by compressing the image area information with these encoding methods, the code amount cannot be adjusted, and when used in a system that stores in a limited memory, there is a risk of causing a memory overload. It was a problem.
[0009]
[Problems to be solved by the invention]
However, conventionally, only compression of image data has been studied, and compression of image area information has been rarely studied. In addition, there is almost no possibility of keeping the code amount after compression of the image area information within a target value, and the image area information is simply encoded using a certain encoding method.
[0010]
The present invention has been made in view of the above-described conventional example, and is an effective image processing apparatus, a control method thereof, and a computer program for storing each of image data and image area information within a code amount within each target value. And a computer readable storage medium.
[0011]
In order to solve this problem, for example, an image processing apparatus of the present invention comprises the following arrangement. That is,
An image processing device that inputs multi-value image data and image area information of each pixel of the multi-value image data and includes independent multi-value image compression means and image area information compression means,
A memory for storing compression-coded multi-value image data and image area information;
The multi-value image compression means includes
A first multi-valued image compression means capable of changing a parameter for determining a compression rate;
A second multi-valued image compressing unit that can change a parameter for determining a compression rate, decodes the code data compressed by the first multi-valued image compressing unit, and re-compresses;
An image data code amount monitoring unit that monitors the code amount generated by the first multi-value image compression unit and determines whether or not the code data amount has reached a predetermined amount;
If the image data code amount monitoring means determines that the predetermined amount has been reached, the compression rate is sent to the first and second multi-value image compression means. Change Image code parameter setting means for setting parameters to be
When the parameter is changed by the image code parameter setting means, the code data previously generated by the first multi-value image compression means is re-encoded by the second multi-value image compression means, and the re-encoding is performed. Is the code data after changing the parameters of the first multi-valued image compression means. Me And let it be stored in Mori
Image compression control means for storing the encoded data generated by the first multi-value image compression means after parameter change in the memory as subsequent code data;
The image area information compression means includes:
First image area information for lossless encoding of the image area information compression Means,
The first image area information compression Image area information encoded by the means Decrypt and degenerate some types of information Second image area information to be losslessly encoded again compression Means,
An image area information amount monitoring means for monitoring the code amount generated by the first image area information compression means and determining whether the code data amount has reached a predetermined amount;
When it is determined by the image area information amount monitoring means that the predetermined amount has been reached, The type of image area information to be reduced The first and second image areas; information To compression means Pa Parameter As Image area code parameter setting means to be set;
When the parameter is changed by the image area code parameter setting means, the code data previously generated by the first image area information compression means is re-encoded by the second image area information compression means, and the re-encoding is performed. Finished Mark Code data as code data after changing the parameters of the first image area information compression means In the memory As well as saving
And image area compression control means for storing the encoded data generated by the first image area information compression means after the parameter change in the memory as subsequent code data.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments according to the present invention will be described with reference to the accompanying drawings. First, basic portions will be described.
[0013]
FIG. 1 is a functional block configuration diagram of an image processing apparatus 100 to which the embodiment is applied. Hereafter, each part of the same figure is demonstrated easily.
[0014]
The image processing apparatus 100 includes an input unit 101 that inputs an image from an image scanner. The input unit 101 may input image data from page description language rendering or the like, or may be realized by reading an image file stored in a storage medium. Anyway.
[0015]
The encoding unit 102 encodes input image data. The encoding method uses a known JPEG encoding method, orthogonally transforms image data corresponding to 8 × 8 pixel units, and performs quantization and Huffman encoding processing using a quantization step described later. .
[0016]
The first memory control unit 103 and the second memory control unit 105 transmit the encoded data (the same encoded data) output from the encoding unit 102 to the first memory 104 and the second memory, respectively. Control is performed so that the data is stored in 106. Here, the first memory 104 is a network device or an image output device for connecting the encoded data finally determined (compressed to the data amount within the target value) outside the basic configuration of FIG. And a memory for holding the encoded data for output to a mass storage device or the like. The second memory 106 is a working memory that assists in the compression encoding process for forming the encoded data on the first memory.
[0017]
The counter 107 counts the data amount of the image data compressed and encoded by the encoding unit 102, holds the count value, and outputs the count result to the encoding sequence control unit 108 that controls the encoding sequence. To do.
[0018]
The encoding sequence control unit 108 detects whether or not the count value of the counter 107 has reached a certain set value. When it is detected that the set value has been reached (exceeded the target value), it has been stored in the memory 104. A control signal is output to the first memory control unit 103 so as to discard the data. The first memory control unit 103 discards the stored data by clearing the memory address counter or clearing the encoded data management table based on this control signal. At this time, the encoding sequence control unit 108 clears the first counter 107 to zero (the input from the input unit 101 continues), and the encoding unit 102 has a higher compression rate than before. To control encoding. That is, control is performed so that the amount of encoded data generated in the encoding process of this apparatus is finally reduced to, for example, ½. In addition, although it set to 1/2 here, it cannot be overemphasized that it can set arbitrarily.
[0019]
The encoded data after the compression rate change is also stored in the first memory 104 and the second memory 106 via the first memory control unit 103 and the second memory control unit 105, respectively, as before. The
[0020]
Furthermore, the encoding sequence control unit 108 reads out the encoded data stored in the second memory 106 so far to the second memory control unit 105 and re-encoding unit 109 serving as encoded data conversion means. A control signal is output to output the encoded data.
[0021]
The re-encoding unit 109 decodes the input encoded data, performs re-quantization to reduce the amount of data, etc., and then performs the encoding process again, and is the same as the encoding unit 102 whose compression rate has been changed. The data amount of the compression rate is output to the second counter 110.
[0022]
The encoded data output from the re-encoding unit 109 is stored in the first memory 104 and the second memory 106 via the first memory control unit 103 and the second memory control unit 105, respectively. Is done.
[0023]
The second memory control unit detects whether or not the re-encoding process has been completed. That is, when there is no more data to be read for the re-encoding process, the encoding sequence control unit 108 is notified of the end of the re-encoding process. Actually, not only the reading process of the second memory control unit 105 but also the process of the re-encoding unit 109 is completed, the encoding process is completed.
[0024]
The count value obtained by the second counter 110 is added to the counter value held by the first counter 107 after the re-encoding process is completed. This addition result represents the total amount of data in the first memory 104 immediately after the re-encoding process is completed. That is, at the time when the encoding process of the encoding unit 102 and the re-encoding unit 109 for one screen is completed, the counter value held in the first counter 107 after the addition is equivalent to one screen. Represents the total amount of data generated when is encoded (details will be described later).
[0025]
The encoding unit 102 continues the encoding process as long as image data from the input unit 101 to be encoded remains, regardless of whether the re-encoding process is completed or not.
[0026]
Whether or not the count value of the counter 107 has reached a certain set value is repeated until the encoding process (encoding and re-encoding) of one page of image data input from the input unit 101 is completed. The re-encoding process is executed under control according to the detection result obtained here.
[0027]
FIG. 8 is a flowchart showing the process flow in the configuration shown in FIG. 1, but for the sake of simplicity, description will be given first according to the simplified flowchart shown in FIG.
[0028]
As described above, the image processing apparatus 100 of the present invention is an apparatus that compresses and encodes one page of image data input from the input unit 101 such as a scanner to a predetermined data amount or less. In order to realize the encoding process, in addition to the input unit 101, an encoding unit 102, a re-encoding unit 109, a first memory 104, a second memory 106, and the like are provided. Using these functional blocks, encoding processing is performed based on the flowchart shown in FIG.
[0029]
The flowchart of FIG. 3 is roughly divided into the following three processing phases.
(1) Encoding phase
(2) Encoding / re-encoding phase
(3) Transfer phase
FIG. 4 to FIG. 7 show how the image data, encoded data, etc. flow and are processed and stored in the memory in each of the above processing phases in an easy-to-understand manner. .
[0030]
FIG. 4 shows an initial state of the encoding phase corresponding to steps S303 and S305 in the flowchart of FIG. 5 shows the processing state of the encoding / recoding phase corresponding to steps S307 to S315, FIG. 6 shows the processing state of the transfer phase corresponding to step S317, and FIG. 7 shows the encoding phase after the transfer phase. Indicates processing status. Hereinafter, each phase will be described.
[0031]
<< Encoding Phase >>
Encoding processing of image data for one page starts from initial setting of encoding parameters (step S301). Here, the upper limit value of the encoded data amount uniquely determined from the image size to be encoded (paper size read from the input unit 101 such as a scanner) or the encoding unit 102 (here, a known JPEG encoding method is used). Parameter such as a quantization step (Q1) to be applied.
[0032]
In step S303, the first counter 107 performs actual encoding processing (JPEG compression in units of 8 × 8 pixels of the image), and cumulatively counts the amount of encoded data to be output.
[0033]
Next, in step S305, it is detected whether the count value of the data amount has exceeded the upper limit value. If not, the JPEG encoding process in step S303 is continued. This is the initial encoding phase.
[0034]
The encoded data output from the encoding unit 102 is stored in both the first memory 104 and the second memory 106 as shown in FIG. A region indicated by vertical stripes represents the stored code.
[0035]
<< Encoding / Recoding Phase >>
When the encoding process of the encoding unit 102 proceeds and the count value of the data amount exceeds the set upper limit value, in step S307, the encoded data in the first memory 104 is discarded and the step In step S309, the quantization step of the encoding unit 102 is changed to Q2.
[0036]
That the count value of the data amount of the encoded data exceeds the set upper limit value means that the data amount after compression does not fall within the target value. Therefore, since it is meaningless to continue the encoding process using the same quantization step, it is changed to the quantization step Q2 having a larger quantization step width than Q1 so that the data amount is smaller than before. is there.
[0037]
After changing the quantization step, in step S311, the encoding process of the encoding unit 102 is restarted, and the encoded data is stored only in the second memory 106 as shown in FIG. In parallel with this, the re-encoding process in step S313 is performed. In the re-encoding process, the encoded data stored in the second memory 106 is read out, re-encoded by the re-encoding unit 109, and stored in the two memories 104 and 106. Then, the encoding process and the re-encoding process are continued until all the codes of the vertical stripes (1) are re-encoded. The re-encoded data output from the re-encoding unit 109 has exactly the same code as the encoded data obtained by encoding in the same quantization step as the encoded data output from the encoding unit 102 after changing the quantization step. Data.
[0038]
Specifically, in this re-encoding process, these values are set to 2 for each quantized value after the encoded data is once Huffman-decoded. ⁿ This is realized by performing a Huffman coding again after performing a bit shift process that produces a result similar to that obtained by dividing by. This method enables high-speed re-encoding processing in that the quantization step is changed only by bit shift and that inverse orthogonal transformation or re-orthogonal transformation processing is not performed. In step 315, the end of the re-encoding process is detected.
[0039]
Since the amount of data after re-encoding is smaller than the amount of encoded data before re-encoding, as shown in FIG. 5, after re-encoding in the memory area where the code before re-encoding was stored Can be stored so as to be overwritten. When the re-encoding process is completed, the data amount of the encoded data of the vertical stripes (1) decreases to the data amount of the encoded data of the diagonal stripes (1) shown in FIG.
[0040]
Steps S307 to 315 described above are processes performed in the encoding / recoding phase.
[0041]
<< Transfer Phase >>
When the re-encoding process is completed, a transfer process is performed in step S317. In the transfer process, as shown in FIG. 6, encoded data of diagonal stripes (2) stored only in the second memory 106 in the encoding / re-encoding phase is converted into diagonal lines ▲ in the first memory 104. It is transferred to the address linked to the encoded data 1) and stored. On the other hand, the encoded data of the diagonal stripe {circle around (1)} and the encoded data of the diagonal stripe {circle around (2)} dispersed on the second memory 106 are continuously stored on the first memory 104. Similarly, the encoded data of the diagonal stripe {circle around (2)} is transferred in the second memory 106 and connected. This is processing performed in the transfer phase.
[0042]
When the transfer phase ends, the process returns to the encoding phase of steps S303 and S305, and the code of the diagonal stripe (4) is output from the encoding unit 102 and stored in the two memories 104 and 106 as shown in FIG. This encoding phase is slightly different from the encoding phase in the initial state (FIG. 4), the quantization step at the time of encoding by the encoding unit 102 is changed from Q1 to Q2, and the two memories 104 and 106 The encoded data stored in is also a collection of codes processed in various phases. If these differences are ignored, the encoding phase immediately after the transfer phase and the initial encoding phase can be regarded as the same.
[0043]
Therefore, by repeating the encoding phase, the encoding / re-encoding phase, and the transfer phase, the code that finally compresses the image data of one page below the data amount setting value is stored in the first memory. I can do it. In addition, the input unit 101 simply continues input until a series of processing is completed. That is, it is not necessary to input the image again from the beginning.
[0044]
The flowchart shown in FIG. 3 describes only the processing corresponding to each phase shown in FIGS. 4, 5, and 6 so that the explanation can be easily understood. In practice, however, the input of image data for one page ends in some phase. Therefore, the correspondence after that is slightly different depending on which phase it is completed. FIG. 8 is a flowchart showing the flow considering this. The flowchart in FIG. 8 considers the relationship between the completion of input of image data for one page and the various processes described with reference to FIG. 3. Here, steps S801, S803, S805, and S807 are added to the flowchart in FIG. It has been added.
[0045]
Steps S801, S803, and S805 detect that the input of image data for one page from the input unit 101 has been completed in the encoding phase, the encoding / recoding phase, and the transfer phase, respectively.
[0046]
If it is detected that the input of image data for one page has been completed in the encoding phase and the transfer phase (steps S801 and S805), the process proceeds to step S807, where the compression encoding process for the page is ended, and the next process is performed. If there is more than one page of image data, the compression encoding process of the next one page of image data is started, and if there is no image data, a stop state is entered.
[0047]
On the other hand, when the end of input of image data for one page is detected in the encoding / re-encoding phase (step S803), the encoding unit 102 needs to stop operation until there is no image data to be re-encoded. Therefore, the encoding process of step S311 is passed, and in step S313, only the re-encoding process for suppressing the image data encoded by the encoding unit 102 so far to a predetermined encoded data amount is continued. And do it. When all the re-encoding processes are completed and the subsequent transfer process is not completed, the encoded data of the entire image data for one page is not collected on the first memory, so the input of the image data for one page is completed. After that, the re-encoding process and the subsequent transfer process need to be performed continuously. In this case, when it is detected in step S315 that all the re-encoding processes have been completed, the encoded data stored only in the second memory 106 is stored in the first memory during the encoding / re-encoding phase. After the transfer to the memory (step S317), in the next step S805, the input end of the image data for one page is detected, and the process proceeds to step S807.
[0048]
The above is the operation, and is also the operation description of FIG.
[0049]
<Modification of memory storage method>
9 and 10 are diagrams showing modifications of the memory storing method shown in the conceptual diagrams of FIGS.
[0050]
In the conceptual diagram of FIG. 5, in the encoding / re-encoding phase, the encoded data output from the encoding unit 102 is stored only in the second memory 106. However, as shown in FIG. During the re-encoding phase, the encoded data output from the encoding unit 102 is directly stored in both the first and second memories.
[0051]
When viewed from the encoding unit 102, encoded data to be encoded and output in any phase is stored in both memories. Further, unlike the conceptual diagram of FIG. 6, as shown in FIG. 10, it is not necessary to transfer data between memories in the transfer phase. In the case of this modification, the encoded data and the re-encoded data are sequentially stored in the order in which they are sent to the first memory 104 in the encoding / re-encoding phase. Therefore, there is a problem that two types of data are mixed.
[0052]
Therefore, in the case of this modification, the encoded data is divided into certain units and managed as a file or a packet in order to cope with this. Specifically, a file management table or a packet management table is created and managed separately.
[0053]
As one method, when data from the encoding unit 102 is stored in the first memory 104, an appropriate unit (for example, 8 × i (i = 1 because the unit of the orthogonal transform is an 8 × 8 block). 2) (integer) for each line), a management number is assigned from the top of the image data, and the storage start address of the encoded data corresponding to each management number and the amount of the encoded data are stored in the order of the management number. Create a management table that can be used.
[0054]
The encoding unit 102 and the re-encoding unit 109 hold the management number of the data being processed, and based on the management number, write the start address and the encoded data amount when storing the encoded data in the management table. In this way, even if the encoded data processed by the encoding unit 102 and the re-encoding unit 109 is randomly stored, the management table is accessed in the order of the management number, and the head address and the encoded data to be read at that time are read. If the encoded data is read from the first memory 104 based on the amount, the encoded data can be read sequentially from the top of the image. Providing such a management mechanism eliminates the need to store continuous data on the image so as to be continuous on the memory.
[0055]
The encoding phase after the transfer phase in the conceptual diagram of FIG. 10 is almost the same as the two encoding phases described above (FIGS. 4 and 7), and the code storage state in the first memory is shown in FIG. It is only slightly different as shown in. Therefore, the above description and this modification are the same in that the three phases are repeated.
[0056]
Next, a second basic configuration example (the configuration described so far is referred to as a first example) for performing a characteristic encoding process in the present invention will be described with reference to FIG.
[0057]
FIG. 2 is a block diagram of the image processing apparatus 200 in the second example.
[0058]
A significant difference from the image processing apparatus 100 of FIG. 1 is that two encoding units that perform encoding first exist in parallel. The image processing apparatus 200 encodes image data input from the input unit 201 in parallel with the first encoding unit 202 and the second encoding unit 205, and two types of encoded data having different compression rates. Is generated. Also in this example, a known JPEG encoding method is used, image data corresponding to 8 × 8 pixel units is orthogonally transformed, and quantization and Huffman encoding processing using quantization steps described later are performed. It is.
[0059]
In this example, a case where the compression rate applied by the second encoding unit 205 is set higher than that of the first encoding unit 202 will be described. Specifically, the quantization step in the first encoding unit 202 is Q1, and the quantization step in the second encoding unit 205 is Q2 (= 2 × Q1).
[0060]
The encoded data output from the encoding unit 202 is stored in the first memory 204 via the first memory control unit 203. At this time, the first counter 208 counts the amount of encoded data output from the encoding unit 202, holds this, and also outputs it to the encoding sequence control unit 209.
[0061]
On the other hand, the encoded data encoded by the encoding unit 205 is stored in the second memory 207 via the second memory control unit 206. At this time, the second counter 210 counts the data amount of the encoded data output from the encoding unit 205 and holds it. Further, when the encoded data stored in the second memory 207 described later is transferred to the first memory 204, the count value is transferred to the first counter 208 at the same time.
[0062]
When the first counter 208 counts the data amount of the encoded data output from the encoding unit 202 and the count value reaches a certain set value, the encoding sequence control unit 209 As in the example, a control signal is issued to the memory control unit 203 so as to discard the data stored in the memory 204.
[0063]
Then, the encoding sequence control unit 209 reads the encoded data stored in the second memory 207, transfers it to the first memory 204, and stores it in the first memory 204. A control signal is output to the memory control unit 203. As a result, the count value of the second counter 210 is transferred to the first counter 208, and the value is loaded (overwritten) as the count value of the first counter.
[0064]
In short, since the count value of the second counter 210 represents the amount of encoded data stored in the second memory 207, the correspondence between the count value and the encoded data is changed. It can be considered that the data is copied to the first counter and the first memory as it is.
[0065]
Furthermore, the encoding sequence control 209 controls the first encoding unit 202 and the second encoding unit 205 so as to perform encoding so that encoded data is smaller than before. Put out.
[0066]
For example, the quantization step S in the first encoding unit 202 and the second encoding unit 205 is switched to twice. As a result, the first encoding unit 202 inherits the quantization step Q2 (= 2 × Q1) in the second encoding unit 205 up to immediately before, and the second encoding unit 205 further Using a large quantization step Q2 × 2, an encoding process with a higher compression ratio in preparation for the next overflow is performed.
[0067]
Here, although the magnification ratio of the quantization step is set to double, it is not limited to this, and needless to say, it can be arbitrarily set. The encoded data output from the switched encoding units 202 and 205 is stored in the corresponding memories 204 and 207 via the corresponding memory control units 203 and 206, respectively.
[0068]
Then, the encoding sequence control 209 reads out the encoded data already stored in the second memory to the memory control unit 206 and sends a control signal to send the data to the re-encoding unit 211. The re-encoding unit 211 performs re-encoding processing of encoded data in the same manner as the re-encoding unit 109 in FIG.
[0069]
The third counter 212 counts the amount of data output from the re-encoding unit 211, is reset to zero immediately before starting the re-encoding process, and counts the output data amount during the re-encoding process. When the re-encoding process is completed, the counter 212 transfers the count value obtained there to the second counter 210.
[0070]
The second counter 210 adds the transferred data amount count value to the counter value held in the second counter 210 to thereby store the code stored in the memory 207 during the re-encoding process. The total data amount of the encoded data and re-encoded data is calculated. That is, the amount of data stored in the memory 207 matches the count value of the counter 210.
[0071]
Regardless of whether the re-encoding process is completed or not, if the image data from the input unit 201 to be encoded remains, the encoding process by the two encoding units 202 and 205 is continued. Then, monitoring whether the count value of the counter 208 has reached a certain set value is repeated until the encoding process (encoding, re-encoding) of image data for one page input from the input unit 201 is completed, The encoding and re-encoding processes described above are executed under control according to the detection result obtained here.
[0072]
FIG. 12 is a flowchart showing the process flow in the configuration of FIG.
[0073]
As described with reference to FIG. 2, when there are two encoding units, image data for one page is encoded based on the flowchart shown in FIG. Note that the description of FIG. 12 is mostly similar to FIG. 8, which is a flowchart in the case of one encoding unit, and those skilled in the art will fully understand the features of the second example from the above description. Since it will be possible, the process will be described in three phases as in the case of one encoder, and the points different from FIG. 8 will be mainly described.
[0074]
The biggest difference between the flow of FIG. 8 described above and the flow of this example is that the transfer processing in step S317 is moved between step S307 and step S309. In short, it can be regarded that the encoding / re-encoding phase and the transfer phase are switched (the exception is the discarded processing of the encoded data in step S307).
[0075]
In the initial setting of the encoding parameter in step S301, the quantization step Q1 is set in the first encoding unit 202, and the quantization step Q2 (= 2 × Q1) is set in the second encoding unit 205.
[0076]
In the encoding phase, steps S801, S303, and S305 are repeatedly executed. Steps S801 and S305 are the same processing as in the case of one encoding unit, but only the encoding processing in step S303 is different as shown in FIG.
[0077]
In order to increase the compression rate of the encoded data stored in the first memory 204 in stages, the encoded data stored first stores the data encoded in the quantization step Q1 having the lowest compression rate. The encoded data stored in the second memory stores the data encoded in the quantization step Q2.
[0078]
When the amount of data stored in the first memory 204 exceeds the set upper limit value (step S305), the encoded data held in the first memory 204 is immediately discarded (step S307). The encoded data having a high compression rate held in the second memory 207 is transferred to the first memory 204 (step S317, see FIG. 14). As a result, without waiting for the end of the first re-encoding process described in the first example (FIG. 1), the encoded data of the appropriate second candidate that does not exceed the upper limit value can be quickly obtained. It can be stored in the memory 207. This is the greatest advantage of applying FIG. 2 with two encoders over FIG.
[0079]
In this second example, since it is a wasteful idea to have encoded data having the same compression rate in the two memories 204 and 207, the second memory 207 has the encoding stored in the first memory 204. The encoded data having a higher compression rate than the data is stored. Accordingly, the subsequent processing is also performed based on this concept, and after the processing (transfer phase) for transferring the encoded data in the second memory 207 to the first memory 204 is completed, the second processing is performed. The encoded data in the memory 207 is re-encoded so as to hold encoded data with a higher one-stage compression rate.
[0080]
Specifically, first, as shown in FIG. 15, in the encoding / re-encoding phase subsequent to the transfer phase, each quantization applied to the two encoding units 202 and 205 before the re-encoding. Steps Q1 and Q2 are changed to Q2 and Q3, respectively (step S309). If the input of one page of image data is not completed (step S803), the subsequent image data is set by a new quantization step. The input data is encoded by the two encoded units (step S311) and stored in the corresponding memories 204 and 207. The encoded data (transferred to the first memory 204) stored in the second memory in parallel with the encoding process is compressed one step higher than the encoded data in the first memory. In order to change to encoded data of rate, the re-encoding unit 211 performs re-encoding processing (S313) so that the data encoded using the quantization step Q3 is obtained, and the re-encoded data is 2 is stored again in the second memory 207.
[0081]
In the second example, as in the first example, in the re-encoding process, these values are set to 2 for each quantized value after the encoded data is once Huffman-decoded. ⁿ This is realized by performing a Huffman coding again after performing a bit shift process that produces a result similar to that obtained by dividing by. This method is capable of high-speed re-encoding processing in that the quantization step is changed only by bit shift and the inverse orthogonal transformation or re-orthogonal transformation processing is not performed.
[0082]
In the case where there are two encoding units as in the second example, as shown in FIG. 15, the encoded data and re-encoded data are mixedly stored in the second memory 207. Will occur. Therefore, as described above, it is necessary for the second memory 207 to manage the encoded data as a file or a packet by dividing the encoded data into a certain unit. For this purpose, for example, a configuration similar to that of the modification of the first example may be provided.
[0083]
In FIG. 12, when the end of the re-encoding process is detected in step S315, the process proceeds to the encoding phase (steps S801 and S303) again. In the encoding phase after the encoding / re-encoding phase, as shown in FIG. 16, the encoded data held in the two memories 204 and 207 not only have different compression ratios but also a mixture of encoded data. The way (address) is also quite different. Accordingly, when the data amount of the first memory 204 again exceeds the set value, the encoded data held in the second memory 207 (the code of the horizontal stripe region of (6) + (8)) Needs to be transferred to the first memory 204. Considering these, it is necessary to manage the encoded data as a file or a packet not only in the second memory 207 but also in the first memory 204. Therefore, the first memory 204 also requires a management mechanism using the above-described management table.
[0084]
The state of the encoding phase shown in FIG. 16 is the initial state of the encoding phase (FIG. 13) except that the method of mixing the quantization step and the encoded data is different before and after the re-encoding process. Is the same. Therefore, by repeating the encoding phase, the transfer phase, and the encoding / re-encoding phase, the encoded data that is finally compressed to be equal to or less than the set upper limit value of the image data for one page is surely stored in the first memory. 204 can be stored.
[0085]
Note that since the arrangement order of the transfer phase and the encoding / re-encoding phase is reversed from the description of the first example, the input end detection of image data for one page, which has been performed after the transfer processing in FIG. (Step S805) has almost the same timing as the input end detection of image data for one page (step S803) performed in the encoding / recoding phase. The two detection processes are functionally the same as step S805 and the timing is the same as step S803. Therefore, these two steps detect the end of input of image data for a new page. Are integrated as a step to be performed and described as step S1201.
[0086]
In the first and second examples described above, the first memory and the second memory have been described as physically separate memories. This is advantageous because access to the two memories can be independent, which is a feature of the present invention. However, the case where the first memory and the second memory are not physically separate memories is also included in the scope of the present invention. Two areas corresponding to the first memory and the second memory are secured on one physical memory, the first memory is the first memory area, and the second memory is the second memory. It can be understood that the present invention can be realized with a single memory by re-reading the above description by rephrasing the area.
[0087]
Further, when each of the above examples is realized with one memory, some of the data transfer processes described in the transfer phase are unnecessary. The details can be easily imagined each time, so the explanation will be omitted. However, when the two areas are used strictly separated, data transfer processing is necessary as in the case of physically having two memories. If the same data is shared between the two areas, not only the data transfer process becomes unnecessary, but also the storage capacity can be reduced.
[0088]
For example, when the encoded data held in the second memory area is transferred to the first memory area, two pieces of information of the head address and the data size in which the encoded data is stored are stored in the second memory. The same effect as that obtained by transferring the encoded data can be obtained only by transferring the data from the control unit to the first memory control unit.
[0089]
When the encoded data is stored in a file format or a packet format, the information transferred between the memory control units is slightly increased, and it is necessary to transfer the management table information related to the encoded data. Nevertheless, it is more efficient than transferring encoded data.
[0090]
Now, according to the above-described image processing apparatus, even when the input image data is encoded, even if it exceeds the target size, processing is performed so that the input is continued and the target size is maintained. In the present invention, in addition to controlling the code amount of the compressed data of the image data, the code amount of the data obtained by encoding the image area information attached to the image data is also controlled in the present invention. Is.
[0091]
The embodiment described below is characterized in that not only an image but also its image area information is encoded. The specific configuration and operation (or processing) will be described below.
[0092]
<First Embodiment>
FIG. 17 shows a first embodiment in which the present invention is applied to the above-described image processing apparatus. In this figure, the present invention is applied to the basic configuration shown in FIG. 1, and the same functional blocks as those in the configuration of FIG.
[0093]
Image data input through the input unit 101 from an image scanner, page description language rendering, or the like is repeatedly encoded and re-encoded based on the processing method already described, and the encoded data falls within the set code amount. .
[0094]
On the other hand, the image data is supplied to an image area information generation unit 1701 to generate the above-described image area information. In this embodiment, since the scanner input image is described, image area information is generated based only on the image data. However, in the case of an image in which a page description language (PDL) is developed and drawn, the PDL information is also referred to. Image area information may be generated. Note that the image area information may be generated by an image input device such as a scanner. In that case, the image area information is also input through the input unit 101, passes through the image area information generation unit 1701, and is sent to the next unit.
[0095]
The image area information generated by the image area information generation unit 1701 indicates, in the embodiment, whether the pixel of interest is a character / line drawing area or a halftone area, and whether it is a chromatic color or an achromatic color. Generate information. Since each pixel can be expressed by 1 bit, a total of 2 bits of image area information (each bit constitutes image area information, and hence each area is referred to as image area component information) is generated.
[0096]
The operation of the image area information generation unit 1701 will be briefly described as follows.
[0097]
First, a determination is made as to whether the area is a character / line drawing area or a halftone area. In the case of a character / line drawing, the luminance (or density) of the character / line drawing changes sharply with respect to the background. On the other hand, when the pixel is in the halftone area, the luminance (or density) of the target pixel has a small change with respect to the adjacent pixel. Therefore, the luminance of the target pixel is set to L _i , L and L _i-1 , L _{i + 1} When defined as
｜ L _i -L _i-1 ｜ ＞ T
Or
｜ L _i -L _{i + 1} ｜ ＞ T
If it is, it can be determined that the pixel of interest is at the edge of the character line image. Here, | x | indicates the absolute value of x.
[0098]
Note that the formula for determining whether or not the density changes sharply is not limited to the above. For example,
｜ 2L _i -L _i-1 -L _{i + 1} ｜ ＞ T
Or may be determined not only in the one-dimensional direction but also in the two-dimensional direction (however, in the case of determining in two dimensions, the image area information generation unit 1701 may Requires a memory for storing image data for a plurality of lines).
[0099]
On the other hand, the determination of chromatic / achromatic color is made. Since the input image data is read by the scanner, the data format is R, G, B.
[0100]
An achromatic color means that each color component of RGB has the same luminance,
R = G = B
Is determined as an achromatic color, and if not satisfied, it is determined as a chromatic color. However, since it is necessary to consider the accuracy of the CCD that the scanner device has,
B−Δ <R <B + Δ
R−Δ <G <R + Δ
G-Δ <B <G + Δ
It may be determined that an achromatic color is satisfied when all of the above are satisfied (Δ is an appropriate small numerical value), and other colors are determined as a chromatic color.
[0101]
In some cases, the RGB color space is converted into, for example, luminance, hue, and saturation (for example, Lab color space), and when the saturation is below a predetermined value, it is determined to be an achromatic color, and when it exceeds a predetermined value, it is determined as a chromatic color. It would be fine.
[0102]
As described above, the image area information generation unit 1701 generates and outputs 2-bit image area information indicating whether the pixel of interest is a character / line drawing / halftone area, a chromatic color or an achromatic color, from the input image data. .
[0103]
Returning to the description of FIG. As described above, the generated image area information is blocked by the blocking unit 1703 to the size of data to be encoded together, for example, the size of M × N (and therefore M × N × 2 bits). Although the block size is 32 × 32, in order to increase the encoding efficiency, it may be more than that, for example, 64 × 64 or 128 × 128, and does not necessarily have to be a square size. Therefore, the size is M × N.
[0104]
By the way, when encoding image area information, multi-value irreversible compression such as JPEG used for compression of normal image data is not suitable. Therefore, we decided to use run-length encoding such as JBIG or PackBits which is lossless compression. The lossless encoding unit 1705 performs lossless encoding on the image area information of the corresponding block.
[0105]
The encoded image area information is stored in the first memory 104 via the first memory control unit 103 and also stored in the second memory 106 via the second memory control unit 105. To do. That is, the encoded image area information is also stored in the two memories at the same time as the encoded image data. At the same time, the code size information output from the lossless encoding unit 1705 is cumulatively counted by the fourth counter 1707 (reset when reading one page is started), and the result is the lossless code. To the control unit 1709.
[0106]
A target value (which can be appropriately changed from the outside) is set in advance in a register in the lossless encoding control unit 1709. When the code amount of the image area information exceeds the target value, the first memory control unit 103, the second memory control unit 105, the lossless encoding unit 1705, and the lossless encoding point encoding unit 1711 Output a control signal. At this time, the fourth counter 1707 is reset.
[0107]
Hereinafter, the operations of the first memory control unit 103, the second memory control unit 105, the lossless encoding unit 1705, and the lossless encoding unit 1711 when receiving this control signal will be described below.
[0108]
First, when the first memory control unit 103 receives the control signal (a signal indicating target value over), the encoded data (image area information) stored in the first memory 104 is discarded. The method of discarding is the same as the method of discarding the encoded data of the image data described above.
[0109]
When the second memory control unit 105 receives this control signal, it reads out the encoded image area information from the second memory 106 and sends the information to the lossless code re-encoding unit 1711.
[0110]
The lossless code re-encoding unit 1711 receives the encoded data from the second memory control unit 105, decodes it, discards a part of the image area information or replaces it with a fixed value, and then performs the lossless encoding again. Do. Although details will be described later, even when a part of the image area information is replaced with a fixed value, the information entropy is reduced, so that the data amount after run-length encoding is reduced. The attribute data after re-encoding is stored again in the second memory 106 (at this stage, it is not stored in the first memory 104). The code amount after re-encoding is counted by a fifth counter 1713. When it is determined that the target value is exceeded, the fifth counter 1713 counts the already encoded data stored in the second memory until the re-encoding is completed, and when the re-encoding is completed. Add to the fourth counter 1707. When the re-encoding is completed, the re-encoded data of the image area information input before the target value over detection stored in the second memory 106 is transferred from the second memory 106 to the first memory. It transfers to 104 at a stretch.
[0111]
On the other hand, when the lossless encoding unit 1705 receives a signal indicating that the target value is exceeded, the image area information input thereafter is converted in the same manner as the lossless code re-encoding unit 1711, that is, the input image area information is converted. (Entropy reduction processing is performed) and encoded.
[0112]
Thereafter, when it is detected that the target value has been exceeded again, the lossless encoding control unit 1709 repeatedly generates a control signal similar to the above. However, the lossless encoding unit 1705 and the lossless code re-encoding unit 1711 change or convert part of the image area component information so that the compression rate is higher than before.
[0113]
The above operation will be described in an easy-to-understand manner as follows.
[0114]
The image area information encoded by the lossless encoding unit 1705 is stored in the first memory 104 and the second memory 106, respectively. When the lossless encoding control unit 1709 detects that the code amount of the image area information exceeds the target value, the lossless encoding control unit 1709 first discards the previously encoded image area information in the first memory 104 and inputs the image area information thereafter. One of the image area component information in the image area information is converted into a fixed value, and a control signal is issued to the lossless encoding unit 1709 so that encoding is performed after changing to an efficient run length.
[0115]
As a result, the image area information input after the target value is exceeded is losslessly encoded at a higher compression rate and stored in the first memory 104. The fourth counter 1707 is reset when it is detected that the target value has been exceeded, and starts counting. However, by adding the value of the fifth counter described below, the fourth counter 1707 The amount of information equivalent to that counted from the beginning is counted.
[0116]
On the other hand, the image area information before the target value is exceeded is discarded from the first memory 104 but remains in the second memory 106. Therefore, the lossless code re-encoding unit 1711 receives and decodes the encoded image area information stored in the second memory 106, and the lossless encoding unit 1705 in which the encoding method is changed. The same encoding is performed and stored in the second memory 106. At this time, the code amount re-encoded by the lossless code re-encoding unit 1711 is counted by the fifth counter 1713. When the re-encoding process by the lossless code re-encoding unit 1711 is completed, the count of the fifth counter 1711 is counted. The result is added to the fourth counter. As a result, the fourth counter counts the same code amount as when the original image was encoded from the beginning.
[0117]
In this way, when re-encoding of the image area information encoded before the target value over detection is completed by the lossless code re-encoding unit 1711, the encoded image area information is stored in the first memory 106 from the first memory 106. When transferred (copied) to the memory, the encoded image area information output from the lossless encoding unit 1705 is stored in both the first memory 104 and the second memory 105.
[0118]
As a result, the image area information before the target value over is re-encoded and stored in the first memory 104, and as a result, the first memory 104 stores the original image. The encoded data of the image area information being currently input from the beginning is stored.
[0119]
Therefore, the first memory 104 also stores a document image (in the embodiment, an irreversible code) compressed by substantially the same processing as the image area information. In this case, both the compressed image data and the compressed image area information are stored in amounts of information equal to or less than the respective target values.
[0120]
The lossless encoding unit 1705 and the lossless code re-encoding unit 1711 are specific means for increasing the run length (processing for increasing the compression rate while being lossless compression). I prepared one.
Process P1: All the chromatic / achromatic identification information at the pixel position where the character / line drawing / halftone pixel identification bit indicates a halftone pixel is changed to a chromatic color.
Process P2: The character / line drawing / halftone pixel identification bit is changed to indicate the halftone pixel.
[0121]
When the encoding control unit 1713 first determines that the target value is exceeded during encoding of the image area information of a certain page, the lossless encoding unit 1705 adopts the above-described processing P1. The lossless code re-encoding unit 1711 is controlled. If it is determined that the target value is exceeded even if this process is performed (when it is determined that the target value is exceeded for the second time), the lossless encoding unit 1705 and the lossless code are used to perform the encoding again using the process P2. The re-encoding unit 1711 is controlled.
[0122]
The reason why the chromatic / achromatic color identification information is chromatic is that the chromatic color space includes an achromatic color in the color space, and thus does not pose a major problem. Also, the character / line drawing / halftone identification information is changed to halftone for the same reason.
[0123]
In any case, since the entropy is reduced by changing the image area information, the amount of information after run-length encoding is reduced stepwise.
[0124]
As a result, both the image data and the image area information can be encoded within the target value (target size) while the input of the image data from the input unit 101 is continued.
[0125]
Next, processing contents for the image area information of the first embodiment will be described. The image area information encoding process is substantially the same as the image data encoding process shown in FIG. 8 except for the process specific to the image area information described below.
(1) Encoding process and lossless encoding process
(2) Change of quantization step and change of image area information conversion process
(3) Re-encoding process and reversible code re-encoding process
The flowchart of FIG. 18 reflects the difference in the above processing in the flowchart of FIG. The processing in steps S303, S309, S311, and S313 in FIG. 8 is replaced with the processing in steps S1803, S1809, S1811, and S1813 in FIG. In the initial setting of the encoding parameter, the upper limit value of the lossless encoded data amount determined by the image size is set in a register in the lossless encoding control unit, and the contents of the image area information conversion process are reset to the initial state. The rest is the same as the flowchart of FIG. That is, the image area component conversion processing in the lossless encoding unit 1705 (and the lossless code re-encoding unit 1711) when the image area information exceeds the target value is performed in step S1809.
[0126]
Next, specific processing contents in this embodiment when 6-bit data “000000” is added to 2-bit image area information per pixel to 8 bits and then Packbits encoding is performed as a lossless code Will be described in more detail with reference to FIG.
[0127]
In the 8-bit data before Packbits encoding, as shown in FIG. 19A, the upper 6 bits are all 0, and the corresponding pixel data is a character / line drawing on the upper side (bit 1) of the lower 2 bits. A flag indicating whether the region is a halftone region, and flag data indicating a chromatic color or an achromatic color is contained in the lower side (bit 0 = LSB). Therefore, the values that the 8-bit data can take are values of 0 or more and 3 or less.
[0128]
It is assumed that the 8-bit data is output from the image area information generation unit 1701 in units of pixels. As specific output data, consider the data shown in FIG.
[0129]
When this is encoded by Packbits, it is compressed into data shown in FIG. In the compressed data, a negative value represents the number of continuous data, and a non-continuous data number represents a positive value. These are length information, and it is possible to determine whether continuous data continues or non-continuous data continues from the sign bit of the length information. Each data after compression is 8 bits (1 byte) as in FIG. The maximum value that can be represented with 1-byte length information is about 128, which is half of 255. If the length information is less than that, it is encoded with a set of length information and the image area flag data group that follows. If it exceeds that, it is divided into a plurality of sets of length information + image area flag data group and encoded.
[0130]
Let us take a closer look at the compressed data in FIG. Since the first length information “−4” is a negative value, it represents the number of continuous data as described above, and represents that four image area flag data “1” immediately after the length information follow.
[0131]
The next data “4” is also length information, but this time is a positive value, indicating that four non-consecutive data continue. Therefore, the four data “2, 3, 2, 3” following the “4” represent discontinuous data. In FIG. 19C, only the positive length information is underlined so that the length information and the image area flag data can be easily distinguished.
[0132]
“−5” next to the non-continuous data is also length information of the continuous data, and represents that five image area flag data “2” immediately after the length information follow. The next underlined data “3” is the length information of the non-continuous data, the following three data “1, 0, 1” are the image area flag data, and the next “−6, 0” is It shows that 6 pieces of data “0” continue.
[0133]
What happens when the reversible code re-encoding unit 1715 re-encodes the compressed data will be described with reference to FIGS. Here, a case will be described in which the chromatic color / achromatic color flag is fixed to “1” in the re-encoding process to make all chromatic colors.
[0134]
The encoded image area information is once decoded and returned to the data of FIG. 19B, and then the flag data is replaced and converted to the data of FIG. 19D. Then, the encoded data shown in FIG. 19E is obtained by performing Packbits encoding on the converted data again. It can be seen that the encoded data of 15 bytes before re-encoding is reduced to 6 bytes after re-encoding.
[0135]
In spite of performing the above re-encoding process, when the count value of the total code amount again exceeds the target value set in the register in the encoding control unit 1713, the re-encoding process ends. If so, the next new re-encoding process is immediately started. If the re-encoding process is not completed, the next new re-encoding process is started immediately after the re-encoding process is completed.
[0136]
In the new re-encoding process, the remaining 1-bit image area flag is also replaced with “1”. As a result, the value of all image area flag data (8 bits) is “3”, and when the number of data bytes is N, the amount of data after encoding is approximately (2N / 128) +2 bytes.
[0137]
This is because every time the number of continuous data exceeds 128, a new set of encoded data (length information and continuous data) of 2 bytes increases.
[0138]
Since the Packbits encoding circuit, decoding circuit, and data conversion circuit are well-known techniques, descriptions of individual circuit configurations are omitted.
[0139]
In the above description, the image area flag of each pixel has been described as 2 bits for simplification. However, as described above, there are some other information as the image area flag. In the re-encoding process, 2-bit image area flag data can be re-encoded up to 2 times, and 4-bit image area flag data can be re-encoded up to 4 times. As the number increases, the number of re-encoding processes can be increased, and the amount of codes can be controlled in multiple stages.
[0140]
Furthermore, if a method for reducing the number of states is used, the amount of codes can be further controlled in multiple stages. For example, in a 2-bit image area flag, four states can be represented, but this is reduced to 3 states by the first re-encoding process and reduced to 2 states by the second re-encoding process. The information entropy before encoding is reduced little by little, and the data amount (code amount) after encoding is reduced finely.
[0141]
If the process of replacing the flag data described above with a fixed value bit by bit is expressed using the term number of states, it can be said that the number of states is reduced by half each time the image area flag data is re-encoded.
[0142]
Naturally, the amount of code can be reduced more finely by reducing the number of states by one than by reducing the number of states by half in one re-encoding process.
[0143]
The processing results when the number of states is reduced by one are shown in FIGS. 20B, 20C, 20D, and 20E, which will be described. FIG. 20A shows the same 2-bit 4-state data as the image area flag data shown in FIG. 19B. The four states are listed again as follows.
(1) Chromatic character part (corresponding to data “3”)
(2) Achromatic character part (corresponding to data “2”)
(3) Chromatic non-character part (corresponds to data “1”, also called chromatic image part)
(4) Achromatic non-character part (corresponding to data “0”, also called achromatic image part)
In the first re-encoding process, two states, (3) chromatic non-character part and (4) achromatic non-character part, are combined into one state (3 ′) Reduce to character. As a result, the following three states are obtained.
(1) Chromatic character part
(2) Achromatic character part,
(3 ') Non-character part
Specifically, the above state is degenerated by replacing data “0” with “1”. The data after the state degradation is changed to the data shown in FIG. When this is Packbits encoded, the encoded data shown in FIG. It can be seen that the code amount is somewhat smaller than that of the encoded data before re-encoding in FIG.
[0144]
In the second re-encoding process, the two states of (1) a chromatic color character portion and (2) an achromatic color character portion are merged and degenerated into one state (1 ′) character portion. As a result, the following two states are obtained.
[0145]
(1 ') Character part
(3 ') Non-character part
This time, the data “2” is replaced with “3” to degenerate the above state. The data after the state degeneration is changed to the data shown in FIG. This data is the same as the data in FIG. The encoded data obtained by packing this into Packbits FIG. 20 (e) is naturally the same encoded data as FIG. 19 (e).
[0146]
When the number of states is reduced by one, the 15-byte data before re-encoding is reduced to 11 bytes by the first re-encoding, and finally reduced to 6 bytes by the second re-encoding. Since it is possible to obtain a code amount that changes finely and decreases in this way, it is possible to obtain compressed data of an image area flag that is close to the target code amount.
[0147]
As described above, the lossless encoding process of the image area flag data is controlled independently of the compression encoding process of the image data, and each is stored in data within the target code amount.
[0148]
The encoded two types of data are multiplexed when output to a network device, an image output device, a mass storage device, or the like connected to the outside. Considering the multiplexing, the unit for encoding the two types of data is matched to the same size as described above, and the encoded data generated by encoding one unit is stored in one packet or file. Manage and store as When multiplexing, two types of packet data having the same image position are connected in the order of, for example, image data and image area data to form one packet and output to the outside.
[0149]
<Second Embodiment>
In the second embodiment, the present invention is applied to the configuration of FIG. 2, and the configuration is shown in FIG. In the figure, the functional blocks used in FIGS. 2 and 17 are used. The same numbers are assigned to the blocks, and the description is omitted.
[0150]
In the second embodiment, two types of image area information having different information entropy are losslessly encoded by the two encoding units in the same way as the image data compression encoding processing in the configuration of FIG. These two encoding units are a first lossless encoding unit 1705 and a second lossless encoding unit 2106. The second lossless transform unit 2106 added in the second embodiment encodes image area information having lower entropy than the first lossless encoding unit.
[0151]
The other blocks added in the present embodiment are only the sixth counter 2108 that counts the code amount output from the second lossless transform unit 2106.
[0152]
In FIG. 21, a block for compressing and encoding image data and a block for reversibly encoding image area information have the following correspondence.
(1) First and second encoding units and first and second lossless encoding units
(2) First, second and third counters and fourth, sixth and fifth counters
(3) Re-encoding unit and lossless code re-encoding unit
(4) Encoding sequence control unit and lossless encoding control unit
Image data is compression-encoded using the former blocks of the above items, and image area information is losslessly encoded using the latter blocks. The two encoding processes are independently controlled in almost the same manner, and each data is compressed to a target code amount or less.
[0153]
The amount of code for image data is gradually reduced by changing the quantization step, but the image area information is losslessly encoded by reducing the number of states of the flag data of the image area information before lossless encoding. The amount of later code is reduced.
[0154]
In the initial state, the first lossless encoding unit 1705 encodes the entire image area information. The second lossless encoding unit 2106 determines the number of states of the flag data of the image area information in the first embodiment. It is reduced by the image area information conversion process described above, and then lossless encoding is performed.
[0155]
When the amount of code output from the first lossless encoding unit exceeds the target value, the lossless code stored in the first memory 104 is discarded and the lossless code stored in the second memory 106 is replaced. Encoded after the lossless code transferred to the first memory, transferred to the first memory, inherited the image area information conversion processing performed by the second lossless encoding unit with the first lossless encoding. Store the data.
[0156]
The second lossless encoding unit performs image area information conversion processing that further reduces the number of states of the flag data than before, and performs lossless encoding. By doing so, the first lossless encoding unit generates a lossless code with a smaller code amount and stores it in the second memory.
[0157]
The lossless code in the second memory that has already been encoded by the second lossless encoding unit, that is, the lossless code transferred to the first memory is decoded by the lossless code re-encoding unit 1711, The reversible code re-encoding unit performs image area information conversion processing so as to have the same number of states as the image area information conversion processing performed by the lossless encoding unit, performs lossless encoding again, and writes back to the second memory. As described above, also in the present embodiment, it is possible to control the code amount by performing the image area information encoding process in the same manner as the image data compression encoding process.
[0158]
Therefore, the flowchart of the above-described process can be used as it is by changing only a part of the expression of the flowchart for compressing and encoding the image data shown in FIG. The parts to be changed are the following three points, as in the first embodiment.
(1) Encoding process → Lossless encoding process
(2) Change quantization step → Change image area information conversion process
(3) Re-encoding process → Lossless code re-encoding process
FIG. 22 shows a flowchart in which the above three points are changed. The four processing contents of steps S2103, S2109, S2111, and S2113 are changed as described above.
[0159]
Since the compression encoding process of image data and the encoding process of image area information are performed in parallel and controlled independently, the second embodiment shown in FIG. 21 is processed according to the two flowcharts of FIGS. A flow can be defined.
[0160]
The processes of the first and second embodiments described above can be realized by a computer program by a general-purpose information processing apparatus (for example, a personal computer) equipped with a multitask OS, including the basic part described first. Therefore, the present invention can also be applied to such a computer program. In this case, those skilled in the art can easily understand that each unit in the block configuration diagrams shown in FIG. 1 and the first and second embodiments can be realized by a module of a computer program or a function program. Therefore, the present invention may be applied to a computer program.
[0161]
In general, when a computer program is installed in a general-purpose information processing apparatus such as a personal computer, it is realized by setting a storage medium (floppy disk, CDROM, MO, etc.) for storing the computer program and installing or copying it. Therefore, the present invention includes such a storage medium as its category.
[0162]
As described above, according to the present embodiment, decoding means for decoding losslessly encoded image area information and a part of the image area information so that the information entropy of the image area information is reduced. Image area information converting means for rewriting or deleting the image area information, re-encoding means for reversibly encoding the image area information obtained by converting the image area information decoded by the decoding means by the image area information converting means, A lossless encoding unit including an information conversion unit, and a storage unit capable of storing data obtained by encoding image area information attached to at least one page of image data, and the amount of the encoded data Accordingly, by controlling both the image area information converting means provided in the reversible converting means and the image area information converting means in the preceding stage of the re-encoding means, the image area information for one page is converted into a desired code. Can be stored in the data volume
[0163]
【The invention's effect】
As described above, according to the present invention, it is possible to encode multi-value image data and its image area information so as to be within a target size without re-inputting multi-value image data.
[Brief description of the drawings]
FIG. 1 is a diagram showing a first basic configuration of an image processing apparatus to which the present invention is applied.
FIG. 2 is a diagram illustrating a second basic configuration of an image processing apparatus to which the present invention is applied.
FIG. 3 is a flowchart showing a simplified process in the configuration of FIG. 1;
FIG. 4 is a diagram illustrating a data flow and memory contents in an encoding phase in an initial state.
FIG. 5 is a diagram showing a data flow and memory contents in an encoding / re-encoding phase.
FIG. 6 is a diagram illustrating a data flow and memory contents in a transfer phase.
FIG. 7 is a diagram illustrating a data flow and memory contents in an encoding phase after a transfer phase.
FIG. 8 is a flowchart showing details of processing in the configuration of FIG. 1;
9 is a diagram showing a data flow and memory contents in an encoding / re-encoding phase in the modification of the configuration of FIG. 1; FIG.
10 is a diagram showing a data flow and memory contents in a transfer phase in the modification of FIG. 9;
11 is a diagram showing a data flow and memory contents in an encoding phase after a transfer phase in the modification of FIG.
12 is a flowchart showing a processing procedure in the configuration of FIG. 2;
13 is a diagram showing a data flow and memory contents in an encoding phase in an initial state in the configuration of FIG.
14 is a diagram showing a data flow and memory contents in a transfer phase in the configuration shown in FIG.
15 is a diagram illustrating a data flow and memory contents in an encoding / re-encoding phase in the configuration of FIG.
16 is a diagram illustrating a data flow and memory contents in an encoding phase after an encoding / re-encoding phase in the configuration of FIG. 2;
FIG. 17 is a block configuration diagram of an apparatus according to the first embodiment of the present invention.
FIG. 18 is a flowchart showing a processing procedure in the first embodiment.
FIG. 19 is a diagram illustrating encoded data of a lossless code and encoded data after re-encoding in the first embodiment.
FIG. 20 is a diagram illustrating another example of encoded data after re-encoding of lossless code and encoded data after re-encoding.
FIG. 21 is a diagram illustrating encoded data after re-encoding of the lossless code and encoded data after re-encoding according to the second embodiment.
FIG. 22 is a flowchart showing a processing procedure in the second embodiment.

Claims (9)

An image processing device that inputs multi-value image data and image area information of each pixel of the multi-value image data and includes independent multi-value image compression means and image area information compression means,
A memory for storing compression-coded multi-value image data and image area information;
The multi-value image compression means includes
A first multi-valued image compression means capable of changing a parameter for determining a compression rate;
A second multi-valued image compressing unit that can change a parameter for determining a compression rate, decodes the code data compressed by the first multi-valued image compressing unit, and re-compresses;
An image data code amount monitoring unit that monitors the code amount generated by the first multi-value image compression unit and determines whether or not the code data amount has reached a predetermined amount;
An image code parameter setting unit that sets a parameter for changing a compression rate to the first and second multi-valued image compression units when the image data code amount monitoring unit determines that the predetermined amount has been reached;
When the parameter is changed by the image code parameter setting means, the code data previously generated by the first multi-value image compression means is re-encoded by the second multi-value image compression means, and the re-encoding is performed. the code data finished the, dissipate stored in the memory as the code data after the parameter change in the first multivalued image compressing means,
Image compression control means for storing the encoded data generated by the first multi-value image compression means after parameter change in the memory as subsequent code data;
The image area information compression means includes:
First image area information compression means for reversibly encoding the image area information;
A second image area information compression means for decoding the encoded image area information, again lossless encoding by degenerated some types of information in the image area information compression means first,
An image area information amount monitoring means for monitoring the code amount generated by the first image area information compression means and determining whether the code data amount has reached a predetermined amount;
If it is determined to have reached the predetermined amount by said image area information amount monitoring means, the type of image area information to be degenerated, the first image area code parameter to be set in the second image area information compression means as parameters Setting means;
When the parameter is changed by the image area code parameter setting means, the code data previously generated by the first image area information compression means is re-encoded by the second image area information compression means, and the re-encoding is performed. the sign-data finished the reduction, causes stored in the memory as the code data after the parameter change in the first image area information compression means,
An image processing apparatus comprising: image area compression control means for storing the encoded data generated by the first image area information compression means after the parameter change in the memory as subsequent code data. The image encoding parameter setting means, whenever it is determined that exceeds the target amount of data, according to claim Paragraph 1, characterized by setting the parameter to be larger than before the quantization steps in the coding Image processing device. The image area code parameter setting means, whenever it is determined that exceeds the target amount of data, setting the parameters for reducing entropy by replacing a part of the image frequency component data constituting the image area information to a fixed value The image processing apparatus according to claim 1, wherein: The image area information includes data indicating whether the pixel of interest is a character / line drawing region or a halftone region, and data indicating whether the pixel of interest is a chromatic color or an achromatic color. The image processing apparatus according to claim 3. When the image area code amount monitoring means first determines that the code data amount exceeds the target data amount, the image area code parameter setting means is an image area of a pixel indicating that the image area code parameter setting means is in a halftone area and is achromatic. set parameters for changing the image area information indicating the chromatic and information,
When the image area code amount monitoring means determines that the code data amount exceeds the target data amount for the second time, the image area code parameter setting means is the image area information of the pixel indicating that it is an achromatic color in the character line image The image processing apparatus according to claim 4, wherein a parameter for changing the image area information to chromatic color is set . Further, by inputting multi-value image data and analyzing the input multi-value image data, attribute component data indicating whether each pixel is a character / line drawing area or a halftone area, and chromatic / the image processing apparatus according to a fourth claims which attribute component data indicating whether the achromatic characterized in that it comprises the image area information generating means for outputting as the image area information. A method of controlling an image processing apparatus that includes multi-value image data and image area information of each pixel of the multi-value image data, and includes an independent multi-value image compression step and an image area information compression step, respectively.
The multi-value image compression step includes:
A first multi-value image compression step in which a parameter for determining a compression ratio can be changed;
A second multi-valued image compressing step that can change a parameter for determining a compression rate, decodes the code data compressed in the first multi-valued image compressing step, and recompresses;
An image data code amount monitoring step of monitoring the code amount generated by the first multi-value image compression step and determining whether or not the code data amount has reached a predetermined amount;
An image code parameter setting step for setting a parameter for changing a compression rate in the first and second multi-valued image compression steps when it is determined that the predetermined amount has been reached by the image data code amount monitoring step;
When the parameter is changed by the image code parameter setting step, the code data previously generated in the first multi-value image compression step is re-encoded by the second multi-value image compression step, and the re-encoding is performed. The code data that has been completed is stored in a predetermined memory as code data after the parameter change in the first multi-value image compression step,
An image compression control step for storing the encoded data generated in the first multi-value image compression step after the parameter change in the memory as subsequent code data,
The image area information compression step includes:
A first image area information compression step for lossless encoding of the image area information;
A second image area information compression step that decodes the image area information encoded in the first image area information encoding step, degenerates some types of information, and performs lossless encoding again;
An image area information amount monitoring step of monitoring the code amount generated by the first image area information compression step and determining whether the code data amount has reached a predetermined amount;
An image area code parameter setting step for setting the type of image area information to be degenerated as a parameter to the first and second image area compression steps when it is determined by the image area information amount monitoring step that the predetermined amount has been reached. When,
When the parameter is changed in the image area code parameter setting step, the code data previously generated in the first image area information compression step is re-encoded in the second image area information compression step, and the re-encoding is performed. The code data that has been converted to the first image area information compression step is stored in the memory as code data after the parameter change in the first image area information compression step ,
A control method for an image processing apparatus, comprising: an image area compression control step for storing encoded data generated in the first image area information compression step after parameter change in the memory as subsequent code data. By reading the computer and executing it, the computer inputs multi-value image data and image area information of each pixel of the multi-value image data, and functions as an independent multi-value image compression means and image area information compression means , respectively. A computer program,
The multi-value image compression means includes
A first multi-valued image compression means capable of changing a parameter for determining a compression rate;
A second multi-valued image compressing unit that can change a parameter for determining a compression rate, decodes the code data compressed by the first multi-valued image compressing unit, and re-compresses;
An image data code amount monitoring unit that monitors the code amount generated by the first multi-value image compression unit and determines whether or not the code data amount has reached a predetermined amount;
If it is determined to have reached the predetermined amount by the image data coding amount monitoring means, and the image coding parameter setting means for setting a parameter for changing the compression ratio to said first, second multi-level image compression means,
If you change the parameters by the image encoding parameter setting means, to re-encode the code data generated previously in the first multi-level image compression means by said second multi-level image compression means, the re-encoding The code data that has been processed is stored in a predetermined memory as code data after the parameter change of the first multi-value image compression means ,
The encoded data generated by the first multi-valued image compression means after the parameter change is caused to function as an image compression control means for storing in the memory as subsequent code data ,
The image area information compression means includes:
First image area information compression means for reversibly encoding the image area information;
A second image area information compression means for decoding the encoded image area information, again lossless encoding by degenerated some types of information in the image area information compression means first,
An image area information amount monitoring means for monitoring the code amount generated by the first image area information compression means and determining whether the code data amount has reached a predetermined amount;
If it is determined to have reached the predetermined amount by said image area information amount monitoring means, the type of image area information to be degenerated, the first image area code parameter to be set in the second image area information compression means as parameters Setting means ;
If you change the parameter by said image region code parameter setting means, the code data generated previously in the first image area information compression means to re-encoding by said second image area information compression means, the recoding the sign-data finished the reduction, causes stored in the memory as the code data after the parameter change in the first image area information compression means,
A computer program that causes the encoded data generated by the first image area information compression means after the parameter change to function as image area compression control means for storing in the memory as subsequent code data. Computer-readable storage medium characterized by storing a computer program according to the eighth claims.

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