JP3840076B2 - Image processing apparatus and method, computer program, and storage medium - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image processing apparatus having a function of compressing and encoding image data with image area information accompanying the image data within a predetermined code amount.
[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 that contain both chromatic and achromatic colors and black characters that are often found 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 conventional example, and provides an effective image processing apparatus for controlling the input of image area information within a code amount within a target value, a control method thereof, a computer program, and a storage medium. It is something to try.
[0011]
[Means for Solving the Problems]
  In order to solve this problem, for example, the image processing of the present inventionMethodHas the following configuration. That is,
  An image processing method for inputting image area information for each pixel of multi-value image data and compressing and encoding the image area information
  A first encoding step for lossless encoding of the input image area information;
  A second encoding step of expanding the lossless encoded data in the first encoding step and lossless encoding again;
  Monitoring the amount of encoded data obtained in the first encoding step, and determining whether or not the amount of encoded data satisfies a predetermined standard,
  When it is determined by the monitoring step that the encoded data amount satisfies a predetermined standard, the first encoding step converts the image area information that is subsequently input according to a predetermined condition, and then performs lossless encoding. In the second encoding step, the image area information represented by the encoded data already encoded by the first encoding means is converted according to a predetermined condition and then re-encoded.
[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.ⁿThis 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 encoding unit, and the differences 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.ⁿThis 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 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]
In the embodiment described below, it will be described how image area information is encoded and the amount of encoded data is controlled.
[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, it is determined whether the area is a character / line drawing area or a halftone area. In the case of a character / line drawing area, the brightness (or density) of the background 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
If all of the above are satisfied, it may be determined as an achromatic color (Δ is an appropriate small numerical value), and the others may be determined as chromatic colors.
[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 third memory 1709 via the third memory control unit 1707. At the same time, the fourth counter 1711 cumulatively counts the amount of code output from the lossless encoding unit 1705 (reset when reading one page is started), and the result is encoded control. It supplies to the part 1713.
[0106]
  The encoding control unit 1713 is provided with a register (not shown), and a target code amount of image area information is preset in this register. The encoding control unit 1713 monitors whether or not the code amount counted by the fourth counter 1711 exceeds the target value. If the encoding control unit 1713 determines that the target value has been exceeded, the encoding control unit 1713Chemical departmentThe following commands are issued to 1705 and the lossless code re-encoding unit 1707, respectively, and the fourth counter 1711 is reset.
[0107]
First, the lossless code re-encoding unit 1707 is instructed to read out the image area data encoded from the third memory 1709 and re-encode it. As a result, the lossless code re-encoding unit 1715 reads the block-unit image area information encoded from the third memory 1709, decodes it once, performs a process to increase the run length, encodes it again, Store in the third memory 1709.
[0108]
The following two methods were prepared for increasing the run length.
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.
[0109]
If the encoding control unit 1713 first determines that the target value will be exceeded while encoding the image area information of a certain page, the encoding control unit 1713 employs the above-described processing P1. And even if this process is performed, when it is determined that the target value is exceeded (when it is determined that the target value is exceeded for the second time), the process P2 is used for the re-encoding.
[0110]
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.
[0111]
In any case, by changing the image area information, the entropy is reduced, so the data amount after run-length encoding is reduced. The attribute data after re-encoding is stored again in the memory 1709 and the code amount is counted by the fifth counter 1717. Then, the lossless code re-encoding unit 1715 performs this process for all codes already encoded by the lossless encoding unit 1705. In this way, when there is a command from the encoding control unit 1713, the encoded data (data encoded by the lossless encoding unit 1705) stored in the third memory 1709 is re-encoded and stored. The code amount at this time is counted by the fifth counter 1715, and the count result is added to the fourth counter.
[0112]
On the other hand, the lossless encoding unit 1705 starts the same processing as the lossless code re-encoding unit 1715 for the block of interest and the following in accordance with an instruction issued when the target value is exceeded from the encoding / encoding control unit 1713. That is, when it is determined that the page is first exceeded after encoding a certain page, a process for increasing the run length is performed on the block from the blocking unit 1703 by the process P1 described above, and the result is encoded. And stored in the third memory 1709. During this time, the amount of code encoded by the lossless encoding unit 1705 starts counting with the fourth counter (reset when it is determined to exceed), but as described above, reversible code re-encoding is performed. Since the encoding unit 1715 also adds the code amount (fifth counter 1717) when re-encoding is performed, as a result, the result of processing P1 on the attribute information for one page The fourth counter 1711 counts the same code amount as.
[0113]
In this way, when it is determined that the target value will be exceeded again while the processing is switched to the process P1 and the image area information is being encoded, the encoding control unit 1713 resets the fourth counter 1711 and reversible code. The control unit 1705 and the lossless code re-encoding unit 1715 are instructed to switch to the process P2 described above.
[0114]
The above is summarized as follows.
[0115]
  The encoding control unit 1713 monitors the encoding amount of the image area information in the lossless encoding unit 1705, and determines that the encoding amount exceeds the target value, the lossless encoding unit 1705 and the lossless code re-encoding. The unit 1715 is set to perform the process P1, and the fourth counter 1711 is reset. Thereafter, the fourth counter 1711 adds the code amount by the lossless encoding unit 1705 and the count value of the fifth counter 1717. Therefore, lossless code re-encodingPartAt the time when the re-encoding by 1715 is completed, substantially the same code amount as that in the process P1 is counted for one image (or one page image) from the beginning. The third memory 1709 stores the encoded data in the process P1.
[0116]
If it is determined that the target value is exceeded again during the processing by the processing P1, this time, the lossless encoding unit 1705 and the lossless code re-encoding unit 1715 are set to perform processing P2, and the fourth counter 1711 and the fifth counter 1717 are reset.
[0117]
As a result, the image area information can be losslessly encoded within the target value (target size) while continuing to input the image data from the input unit 101.
[0118]
Next, a flowchart showing the processing contents of the first embodiment is shown in FIG. 18, and the description will be given using this flowchart. As described above, the process according to the present embodiment is roughly divided into two processes. One is a lossless encoding process and the other is a re-encoding process.
[0119]
The encoding process includes an image area information conversion process in step S1805 and a lossless encoding process in step S1807. The re-encoding process includes a decoding process in step S1815, an image area information conversion process in step S1817, and a step. And the re-encoding process of S1819.
[0120]
The other steps are conditional branching and start and end steps, except for the change in the image area information changing process of S1813.
[0121]
First, encoding processing of image area information is started from step S1801. In the next step S1803, it is detected whether or not the input of image area information for one page of the image has been completed. If it has been completed, the process proceeds to step S1821, and if it has not been completed, that is, the input of image area information has been completed. If there is, the image area information conversion process in step S1805 is performed.
[0122]
In the initial state where the re-encoding process has not been started yet, nothing is performed in the image area conversion process, and the input image area information is directly encoded by the lossless encoding process in the next step S1807.
[0123]
In the next step S1809, it is determined whether or not the re-encoding process is being performed. If the re-encoding process is being performed, the re-encoding process including steps S1815 to S1819 is performed. For example, the process goes to step S1811 to determine whether or not the encoded data (code amount) exceeds the set value.
[0124]
If not, the process returns to step S1803, and the encoding process is repeated. If it is over, the processing content in the image area information conversion process is changed. With this change, the contents of the image area conversion processing in steps S1805 and S1817 change. Specifically, in the initial state, processing P1, that is, the chromatic / achromatic color at the pixel position in which the character / line drawing / halftone identification information is determined to be halftone in the input image area information. All of the identification information is chromatic.
[0125]
After changing the image area information conversion processing content, re-encoding processing is performed. In the re-encoding process, in step S1815, the encoded image area information is decoded and returned to the data before encoding. In the next step S1817, the image area information conversion process is performed, and the image area information change process is performed. In the next step S1819, the converted image area information is losslessly encoded again.
[0126]
When the re-encoding process is completed, the process returns to step S1803, and if there is input of image area information, it is encoded. If the code amount exceeds the set value even once, the image area information conversion process content is changed, and after the image area information conversion process in step S1805 is replaced with the process P1, the lossless encoding is performed in step S1807. .
[0127]
Thus, after replacing the process P1, if it is determined again in step S1811 that the code amount has exceeded the target value, in step S1813, the image area change in steps S1805 and S1817 is changed to the process P2. To do.
[0128]
In any case, if all the input of the image area information is completed and the re-encoding process is not performed, the process proceeds to step S1823, and the image area information encoding process is ended.
[0129]
As described above, according to the first embodiment, image data is encoded within a target size without interrupting or re-inputting one or one page of image data, The image area information of the image can be losslessly encoded within the target size.
[0130]
An example in which the lossless encoding unit and the lossless code re-encoding unit in the embodiment employ packbits encoding will be described below.
[0131]
Here, specific processing in this embodiment when 6 bits data “000000” is added to 2 bits image area information per pixel to 8 bits and then Packbits encoding is performed as a lossless code. The contents will be described with reference to FIG.
[0132]
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 identifies the character / line drawing / halftone on the upper side of the lower 2 bits. It is assumed that a flag indicating chromatic / achromatic color is stored in the lower side. Therefore, the values that the 8-bit data can take are values of 0 or more and 3 or less. In order to simplify the description, it is assumed that one-dimensional image area information is output from the image area information generation unit 1701.
[0133]
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.
[0134]
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 (b). 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.
[0135]
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.
[0136]
The next data “4” is also length information, but this time is a positive value, which indicates that four non-continuous data continues. Therefore, the four data “2, 3, 2, 3” following “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.
[0137]
“−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 length information of non-continuous data, the following three data “1, 0, 1” are image area flag data, and the next “−6, 0” It shows that 6 pieces of data “0” continue.
[0138]
What happens when the reversible code re-encoding unit 1715 re-encodes the compressed data will be described with reference to FIGS. In order to simplify the description, a case will be described in which all the chromatic colors are fixed by fixing the bits of the chromatic color / achromatic color flag to “1” in the re-encoding process.
[0139]
The encoded image area data is once decoded and returned to the data of FIG. 19B, and then converted to the data of FIG. 19D by replacing the flag data. If this is encoded again with Packbits, the encoded data shown in FIG. It can be seen that the encoded data of 15 bytes before re-encoding is reduced to 6 bytes after re-encoding.
[0140]
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.
[0141]
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.
[0142]
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.
[0143]
Since the Packbits encoding circuit, decoding circuit, and data conversion circuit are well-known techniques, descriptions of individual circuit configurations are omitted.
[0144]
In the above embodiment, for the sake of simplification, the image area flag of each pixel has been described as 2 bits. However, as described above, other information may be added as the image area flag.
[0145]
Theoretically, the process for converting the image area information is 2 if the type of the image area is N bits.^NThere will be. However, the compression ratio needs to be high every time conversion is performed. In any case, the larger the number of bits of the image area information, the more the number of re-encoding processes can be increased, and the code amount can be controlled in multiple stages.
[0146]
As described above, the lossless encoding process of the image area information data is controlled independently of the compression encoding process of the image data, and each is stored in data within the target code amount.
[0147]
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. In consideration of the multiplexing, the units for encoding the two types of data are matched to the same size, and the encoded data generated by encoding one unit is managed and stored as one packet or file. . 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.
[0148]
Since the two encoding processes are controlled independently, the image data compression encoding processing unit may have another configuration. Therefore, even if units 1701 to 1717 for performing lossless encoding processing on image area information data are added to the configuration of FIG. 2, the same processing can be performed. The configuration is shown in FIG. 20. The operations of the units 1701 to 1717 are exactly the same as those in FIG. 17, and the operation of the image data compression portion is also exactly the same as the operation in FIG.
[0149]
<Modification of First Embodiment>
In the above-described embodiment, two bits of the image area component information are a character / line drawing / halftone identification bit, the other is a chromatic / achromatic bit, and has a value of 0 to 3 as one value. Treated as a thing. However, the character / line drawing / halftone identification information and the chromatic / achromatic identification information are originally independent information. Therefore, a block composed of character / line drawing / halftone identification bits and a block composed of chromatic / achromatic identification bits may be made independent and encoded independently. . As a result, each bit in each block is composed of only the same type of bits, so that compression efficiency can be increased in the first stage, and as a result, some bits of image area information are fixed. By reducing the probability of conversion to a value, it is possible to increase the probability of compression encoding with the original image area information.
[0150]
<Second Embodiment>
In the second embodiment, a description will be given of a processing method capable of finely controlling the amount of code by increasing the number of re-encoding processes even when the number of bits of image area information is the same as that in the first embodiment. The configuration of this embodiment is the same as that of the first embodiment, and the difference is the image area flag data compression method in the lossless encoding unit 1705 and the lossless code re-encoding unit 1715.
[0151]
In the first embodiment, the image area flag data is replaced with a fixed value bit by bit, but in the second embodiment, the number of states is degenerated. 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, and the data amount (encoding amount) after encoding is reduced finely.
[0152]
When the first embodiment is expressed using the term number of states, it can be said that the number of states is reduced to half each time image area information is re-encoded.
[0153]
In the first embodiment, the number of states is substantially halved in one re-encoding process, whereas in the present embodiment, the number of states is reduced by one, so that the code amount can be reduced finely. Naturally.
[0154]
The processing result of the second embodiment will be described with reference to FIGS.
[0155]
FIG. 19A shows the same data as the image area flag data shown in FIG. 19B, in which all of the two 2-bit states exist. The definition of the four states is as follows.
(1) Chromatic character line drawing (corresponding to data “3”)
(2) Achromatic line drawing (corresponding to data “2”)
(3) Chromatic halftone (corresponds to data “1”, also called chromatic image part)
(4) Achromatic halftone (corresponds to data “0”, also called achromatic image part)
In the second embodiment, in the first re-encoding process, two states of (3) chromatic halftone and (4) achromatic halftone are combined into one of the above four states. State (3 ′) is degenerated to a halftone. As a result, the following three states are obtained. This corresponds to the process P1.
(1) Chromatic character part
(2) Achromatic character part,
(3 ') Halftone
Specifically, the above state is degenerated by replacing data “0” with “1”. The data after the state degeneration is changed to the data shown in FIG. If 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.
[0156]
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.
(1 ') Character part
(3 ') Non-character part
This time, the data “2” is replaced with “3” to reduce the 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. Encoded data obtained by Packbits encoding FIG. 21 (e) is naturally the same encoded data as FIG. 19 (e).
[0157]
In the first embodiment, the 15-byte data before re-encoding is reduced to 6 bytes by one re-encoding, but in this embodiment, it is reduced to 11 bytes by the first re-encoding, and 2 It is finally reduced to 6 bytes by the second re-encoding. Eventually, in the second embodiment, it is possible to obtain a code amount that varies finely and decreases that cannot be obtained in the first embodiment. Therefore, compressed image area flag data close to the target code amount can be obtained.
[0158]
<Application example>
In the first embodiment and its modifications, and in the second embodiment, an apparatus for reading an image from an image scanner is taken as an example, and the functional operation of the apparatus has been described. Most of the functions (including the encoding process) can be realized by the computer program as described above.
[0159]
Therefore, the present invention may be applied to an application program that operates on a general-purpose information processing apparatus such as a personal computer. In the case of application to an application program, a GUI may be provided such as allowing the user to specify an image file to be compressed and allowing the user to select a target size. The target value at this time can be set arbitrarily by the user, but setting with numerical values is difficult to understand, so it should be selected from an intuitive menu that takes into account the document size and image quality (high, medium, low, etc.). It would be good to make a decision.
[0160]
Further, although the quantization step has been described as an example of the encoding parameter of the encoding unit, when data having different compression ratios are mixed, as long as the image quality between them does not cause a sense of incongruity, other The parameters may be used. However, for example, in the configuration of FIG. 1, in order to make the re-encoded data from the re-encoding unit 109 substantially the same as the encoded data from the encoding unit 102 after the parameter change, the above-described implementation is required. As shown in the embodiment, a method of increasing the quantization step is preferable.
[0161]
Further, as described above, the present invention can be realized by an application program that runs on a general-purpose device, and therefore the present invention includes a computer program. In addition, since the computer program is usually performed by setting or copying or installing a storage medium such as a floppy disk or CDROM in the apparatus, such a storage medium is naturally included in the scope of the present invention.
[0162]
In the embodiment, the image data is input from the scanner. However, the present invention may be applied to a printer driver that operates on a host computer. In the case of application to a printer driver, when data to be printed is received from a higher-level process (such as an application), it is of course possible to determine whether the data is a halftone image or a character / line image. The configuration related to the area information generation processing can be omitted or simplified.
[0163]
The present invention can also be applied to a combination of a computer program and appropriate hardware (such as an encoding circuit).
[0164]
As described above, according to the first and second embodiments, the decoding means for decoding losslessly encoded image area information and 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 a part of the image area information, and re-encoding 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. Encoding means, lossless encoding means including the information conversion means, and storage means capable of storing data obtained by encoding image area information associated with image data for at least one page,
By controlling both the image area information converting means provided in the lossless converting means and the image area information converting means in the preceding stage of the re-encoding means according to the amount of the encoded data, an image for one page is obtained. The area information can be contained in a desired encoded data amount.
[0165]
<Third Embodiment>
The third embodiment will be described. The third embodiment performs substantially the same operation as the first embodiment described above, but the structure is different. FIG. 22 is a block configuration diagram thereof. The constituent elements having the same reference numerals as those in FIG. 1 have the same operation (encoding process of image data), and therefore the description thereof will be omitted. Hereinafter, the encoding part of the image area information in the third embodiment will be described. explain.
[0166]
Image data (multi-valued color image data) input via the input unit 101 from an image scanner, page description language rendering, or the like is supplied to the encoding unit 102 and also to the image area information generation unit 2201. As described above, since the encoding unit 102 and the subsequent steps are the same as those in FIG. 1, the description thereof is omitted.
[0167]
The image area information generation unit 2201 generates image area information from the input image data. When the input target is a scanner, the same processing as that of the image area information generation unit 1701 in the first embodiment described above may be performed, and in the case of PDL rendering, when developing an image by PDL rendering. Since the image area information is known for each pixel, the information may be used.
[0168]
The generated image area information is blocked by a blocking unit 2202 to a data size to be encoded together, for example, a size of M × N.
[0169]
Multi-value irreversible compression such as JPEG used for compressing image data is inconvenient for use in compressing image area information that is a collection of binary data. Therefore, a run such as JBIG or PackBits that is reversible compression is used. The lossless encoding unit 2203 performs lossless encoding using length encoding.
[0170]
The reversibly encoded image area information is stored in the first memory 104 via the memory control unit 2204.
[0171]
FIG. 27 shows the state of the memory in the initial state of encoding. 4 is different from FIG. 4 in that a storage area for image area information is provided as shown. The encoded image area information is sequentially stored in this storage area via the memory control unit 2204.
[0172]
As described above, the coding sequence control unit 108 detects whether or not the count value of the first counter 107 has reached a certain set value, and when it has detected that the set value has been reached, a predetermined control signal And the encoding unit 102 is controlled to encode the image data at a higher compression rate than before.
[0173]
In the third embodiment, at the same time, the encoding sequence control unit 108 synchronizes with the re-encoding timing of the image data described above, and instructs the encoding control unit 2205 to re-encode the image area information. To instruct.
[0174]
The encoding control unit 2205 reads the encoded image area data from the first memory 104 and outputs a control signal to the memory control unit 2204 so as to send the data to the lossless code re-encoding unit 2206.
[0175]
When the lossless code re-encoding unit 2206 receives the encoded data, the lossless code re-encoding unit 2206 discards or replaces a part of the plurality of attribute flag data with a fixed value, and then performs lossless encoding again. Even when a part of the attribute flag 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 first memory 104.
[0176]
On the other hand, the encoding control unit 2205 performs image area information conversion provided in the lossless encoding unit 2203 so as to encode attribute flag data whose information amount has been reduced in the lossless code re-encoding unit 2206 and attribute flag data of the same information. A control signal is sent to the processing unit so that part of the attribute flag is discarded or replaced with a fixed value, and the encoding process is continued.
[0177]
The process is continued until the image area flag data to be re-encoded disappears and the re-encoding process is completed.
[0178]
The encoding sequence control unit 108 detects whether or not the count value of the counter 107 has reached a certain set value, and every time the target value is exceeded or image data is re-encoded, the image sequence is synchronized with that. By increasing the number of attribute flags to be discarded by the area flag, the code amount of the image area data can be reduced stepwise, and the code amount of the image area data can be kept within the target value.
[0179]
Next, the processing content (encoding process of image area information) of the third embodiment will be described with reference to the flowchart of FIG. The process of the third embodiment is roughly divided into two processes as described above. One is a lossless encoding process and the other is a re-encoding process.
[0180]
The encoding process is realized by the image area information conversion process in step S2305 and the lossless encoding process in step S2307. The re-encoding process is realized by the decoding process in step S2315, the image area information conversion process in step S2317, and the re-encoding process in step S2319.
[0181]
The other steps are conditional branch and start and end steps, except for the change in the image area information change processing in S2313.
[0182]
First, from step S2301, encoding processing of image area information is started. In the next step S2303, it is detected whether or not the input of the image area information for one page of the image has been completed. If it has been completed, the process goes to step S2321, and if it has not been completed, that is, the input of the image area information has been completed. If there is, the image area information conversion process in step S2305 is performed.
[0183]
In the initial state where the re-encoding process has not been started yet, nothing is performed in the image area conversion process, and the input image area information is directly encoded in the lossless encoding process of the next step S2307.
[0184]
In the next step S2309, it is determined whether or not the re-encoding process is being performed. If the re-encoding process is being performed, the re-encoding process including steps S2315 to S2319 is performed. In step S2311, it is determined whether re-encoding of the image data is performed.
[0185]
If the control signal that the encoded data has exceeded the predetermined target value has not been received from the encoding sequence control unit 108, the process returns to step S2303, and the encoding process is repeated. Changes the processing contents in the image area information conversion processing. With this change, the contents of the image area conversion processing in steps S2305 and S2317 are changed. Specifically, in the initial state, the input image area information has been encoded without invalidating even one bit. That is, nothing was done in the image area conversion process, but after changing the processing contents, at least one bit in the image area information is discarded or replaced with a fixed value in the image area conversion process. . For example, all the bits indicating a character / line image are converted into bits indicating halftone. Thereafter, each time the processing content is changed, the number of bits of the image area flag to be discarded or replaced with a fixed value is increased (a state in which the run length is likely to be long).
[0186]
After changing the image area information conversion processing content, re-encoding processing is performed. In the re-encoding process, in step S2315, the encoded image area information is decoded and returned to the data before encoding. In the next step S2317, the image area information conversion process is performed, and a part of the image area information is discarded or replaced with a fixed value. In the next step S2319, the converted image area information is losslessly encoded again.
[0187]
When the re-encoding process is completed, the process returns to step S2303, and if image area information is input, it is encoded. When the code amount of the image data exceeds the set value even once and re-encoding is started, the image area information conversion processing content is changed in conjunction with it, and part of the image area information conversion processing in step S2305 After the image area flag data is discarded or replaced with a fixed value, lossless encoding is performed in step S2307.
[0188]
If the re-encoding process continues even after all the image area information has been input, the process proceeds from step S2303 to step S2321, where it is determined that the re-encoding process is in progress, and the steps S2315˜ The re-encoding process consisting of S2319 is performed.
[0189]
If all the input of the image area information is completed and the re-encoding process is not performed, the process proceeds to step S2323, and the image area information encoding process is ended.
[0190]
Further, when the code amount of the image data once exceeds the set value even once, all the bits indicating the chromatic color / achromatic color in the image area information are changed to chromatic colors.
[0191]
Next, the third embodiment in the case where Pac kbit s encoding is performed as a lossless code after 6-bit data “000000” is added to 2-bit image area information per pixel to form 8 bits. The specific processing contents in will be described in more detail with reference to FIG.
[0192]
As shown in FIG. 24A, the upper 6 bits are all 0, and the corresponding pixel data is the character line drawing area on the upper side of the lower 2 bits. , Halftone or flag bits, and flag bits representing chromatic or achromatic colors are assigned to the lower side. Therefore, the values that the 8-bit data can take are values of 0 or more and 3 or less.
[0193]
It is assumed that the 8-bit data is output from the image area information generation unit 2201 in units of pixels. As specific output data, consider the data shown in FIG.
[0194]
When this is packed bits encoded, it is compressed into the 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.
[0195]
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.
[0196]
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. 9C, only the positive length information is underlined so that the length information and the image area flag data can be easily distinguished.
[0197]
“−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.
[0198]
What happens when the above-described compressed data is re-encoded by the lossless code re-encoding unit 1715 will be described with reference to FIGS. Here, an example will be described in which, in the re-encoding process, the chromatic / achromatic color flag is fixed to “1” to make all chromatic colors.
[0199]
The encoded image area data is once decoded and returned to the data shown in FIG. 5B, then the flag data is replaced and converted into the data shown in FIG. Then, the encoded data shown in FIG. 5E 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.
[0200]
Even after performing the above-described re-encoding process, in the case of encoding image data, if the count value of the total code amount again exceeds the set target value and the image data is re-encoded, the encoding is performed. When a control signal indicating that the image area data is also re-encoded is received from the sequence control unit 108 and the re-encoding process is completed, 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.
[0201]
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.
[0202]
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.
[0203]
Since the Packbits encoding circuit, decoding circuit, and data conversion circuit are well-known techniques, explanations of the specific arrangements are omitted.
[0204]
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.
[0205]
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.
[0206]
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. In consideration of the multiplexing, the units for encoding the two types of data are matched to the same size, and the encoded data generated by encoding one unit is managed and stored as one packet or file. . 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.
[0207]
Since the two encoding processes are controlled independently, the image data compression encoding processing unit may have another configuration. Therefore, even if units 2201 to 2206 for performing lossless encoding processing on the image area flag data are added to the configuration of FIG. 2, the same processing can be performed. The configuration is shown in FIG. 25. The operations of the units 2201 to 2206 are exactly the same as those in FIG. 22, and the operation of the image data compression portion is also exactly the same as the operation in FIG.
[0208]
<Fourth Embodiment>
In the fourth embodiment, a description will be given of a processing method capable of finely controlling the code amount by increasing the number of re-encoding processes even if the number of bits of image area information is the same as that of the third embodiment. The configuration of this embodiment is also the same as that of the first embodiment, and the difference is the image area flag data degeneration method in the lossless encoding unit 1703 and the lossless code re-encoding unit 1706.
[0209]
In the first embodiment, the image area flag data is replaced with a fixed value bit by bit, that is, the data is degenerated bit by bit. In the present embodiment, the number of states is degenerated. 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, and the data amount (code amount) after encoding is reduced finely.
[0210]
When the third embodiment is expressed using the term number of states, it can be said that the number of states is reduced to half each time image area flag data is re-encoded.
[0211]
While the third embodiment reduces the number of states by half in one re-encoding process, the present embodiment reduces the number of states one by one, so it is natural that the code amount can be reduced finely. It is.
[0212]
The processing results of this embodiment are shown in FIGS. 26B, 26C, 26D, and 26E, and will be described.
[0213]
FIG. 26A shows the same data as the image area flag data shown in FIG. The four states are listed again as follows.
[0214]
(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 present embodiment, in the first re-encoding process, two states of (3) a chromatic non-character portion and (4) an achromatic non-character portion are combined into one state among the four states. (3 ′) Reduce to a non-character part.
As a result, the following three states are obtained.
[0215]
(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 packedbits 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 shown in FIG.
[0216]
In the second re-encoding process, the two states of (1) the chromatic color character portion and (2) the achromatic color character portion are merged to be reduced to one state (1 ′) character portion. As a result, the following two states are obtained.
[0217]
(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 encoding this by Pac kbit s FIG. 26 (e) is naturally the same encoded data as FIG. 24 (e).
[0218]
In the third embodiment, 15-byte data before re-encoding is reduced to 6 bytes by one re-encoding, but in the fourth embodiment, it is reduced to 11 bytes by the first re-encoding. In the second re-encoding, it is finally reduced to 6 bytes. Eventually, in the fourth embodiment, it is possible to obtain a code amount that changes finely and decreases that cannot be obtained in the third embodiment, and therefore it is possible to obtain compressed data of an image area flag close to the target code amount.
[0219]
As described above, according to the third and fourth embodiments, similarly to the first and second embodiments described above, the image area information for one page can be contained in a desired encoded data amount. it can.
[0220]
<Fifth Embodiment>
The fifth embodiment will be described. The fifth embodiment performs substantially the same operation as the first embodiment described above, but the structure is different. FIG. 28 is a block configuration diagram thereof. Since the operations (image data encoding process) are the same as those of the constituent elements having the same reference numerals as those in FIG. explain.
[0221]
Image data (multi-valued color image data) input via the input unit 101 from an image scanner, page description language rendering, or the like is supplied to the encoding unit 102 and also to the image area information generation unit 2801. As described above, since the encoding unit 102 and the subsequent steps are the same as those in FIG. 1, the description thereof is omitted.
[0222]
The image area information generation unit 2801 generates image area information from the input image data. When the input target is a scanner, the same processing as that of the image area information generation unit 1701 in the first embodiment described above may be performed, and in the case of PDL rendering, when developing an image by PDL rendering. Since the image area information is known for each pixel, the information may be used.
[0223]
The generated image area information is blocked by a blocking unit 2803 into a data size to be encoded together, for example, a size of M × N.
[0224]
Multi-level lossy compression such as JPEG used for compressing image data is inconvenient to use for compressing image data, which is a collection of binary data. The image area information is losslessly encoded by the lossless encoding unit 2805 using length encoding.
[0225]
The encoded image area information is stored in the first memory 104 via the third memory control unit 2807. At the same time, the amount of code data output from the lossless encoding unit is cumulatively counted by the fourth counter 2811, and the count value is sent to the encoding control unit 2813.
[0226]
FIG. 33 shows the state of the memory in the initial state of encoding. The difference from FIG. 4 is that an image area information storage area is provided. Basically, the encoded image area information is sequentially held in this storage area, but the encoded image data can also be stored in this storage area, as will be described later. Further, even if the encoded image area data does not fit in this storage area, if there is a surplus in the image data storage area, it is of course possible to hold it in the surplus storage area. is there.
[0227]
The encoding control unit 2813 and the encoding sequence control unit 108 send the count values from the fourth counter 2811 and the first counter 107 to the sixth counter 2809, respectively.
[0228]
The sixth counter adds up the counts of the encoding of the image data and the encoding of the image information, and sends the count value to the image / image area encoding control unit 2819.
[0229]
A total target value of image data and image area data is set in a register in the image / image area encoding control unit 2819, and the total count value of the code amount of the image data and image area data is set to a target value. When over, a control signal is output to the encoding control unit 2813 and the encoding sequence control unit 108 so as to perform re-encoding processing.
[0230]
The encoding control unit 2813 reads the encoded image area data from the first memory 104 and outputs a control signal to the memory control unit 2807 so as to send the image area data to the lossless code re-encoding unit 2815.
[0231]
The encoding sequence control unit 108 outputs a control signal to the first memory control unit 103 so as to discard the data stored in the first memory 104. 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 the control signal. The encoding sequence control unit 108 controls the encoding unit 102 to perform encoding at a higher compression rate than before, and performs re-encoding processing.
[0232]
That is, even if the count value of the first counter 107 exceeds the target value of the code amount of the image data stored in the register in the encoding sequence control unit 108, or the count value of the fourth counter 2811 Even if the value exceeds the target value of the code amount of the image area data stored in the register in the encoding control unit 2813, the target value of the code amount of the image data and the daily sign of the code amount of the image area data If the sum of the code amounts of the image data and the image area data does not exceed the sum of the values, the encoding process is continued.
[0233]
As a result, for example, the image data slightly exceeds the target value of the image data, but the code amount of the image area information corresponding to the image data is small, so that the image data is assigned to the image area data in the first memory 104. If the sum of the code amount of the image data and image area information falls within the target value of the code amount of the image data and the image area data, the image data is re-encoded. There is no need. This eliminates the need for further high compression, leading to improved image quality and performance.
[0234]
In the re-encoding process of the image data, when a control signal for the re-encoding process is output from the image / image area encoding control unit 2819 to the encoding sequence control unit 108, the encoding sequence control unit 108 Control for performing re-encoding processing as described above in the description of 1 is performed.
[0235]
When the control signal for the re-encoding process is output from the image / image area encoding control unit 2819 to the encoding control unit 2813, the encoding control unit 2813 The encoded image area data is read from the memory 104 and a control signal is output to the memory control unit 2807 so as to send the data to the lossless code re-encoding unit 2815.
[0236]
When the lossless code re-encoding unit 2815 receives the encoded data, it decodes it, discards some of the attribute information or replaces it with a fixed value, and then performs lossless encoding again. Even when a part of the attribute flag is replaced with a fixed value, the information entropy decreases, so the data amount after run-length encoding decreases. The attribute data after re-encoding is stored again in the first memory 104 and the code amount is counted by the fifth counter 2817.
[0237]
On the other hand, like the lossless code re-encoding unit 2815, the encoding control unit 2813 sends a control signal to the lossless encoding unit 2805 to discard part of attribute information input thereafter or to replace it with a fixed value. Send and continue the encoding process. At the same time, a control signal is also sent to the fourth counter 2811 to reset the value that has been counted and held so far, and a part of the attribute information is discarded or replaced with a fixed value and then generated by encoding processing. The code amount to be counted is newly counted.
[0238]
When the image area information to be re-encoded disappears and the re-encoding process is completed, the count value of the fifth counter 2817 is transferred to the fourth counter 2811 and added. As a result, the counter 2811 counts the total code amount of the lossless encoded data after the attribute information is partially discarded or replaced with a fixed value.
[0239]
Each time image data and image area information are re-encoded, the respective code amounts are counted, and the total value of the code amounts of the image data and image area information is stored in a register in the image / image area encoding control unit 2819. Each time the sum of the image data and the target value of the image area information is exceeded, image data re-encoding processing and image area information re-encoding processing are performed. Re-encoding of image area information can reduce the code amount of image area data in a stepwise manner by increasing the number of attribute flags to be discarded, and the code amount of the image area information can be kept within the target value. It becomes.
[0240]
Next, the processing contents of this embodiment will be described with reference to the flowchart of FIG. As described above, the process according to the present embodiment is roughly divided into two processes. One is a lossless encoding process and the other is a re-encoding process.
[0241]
The encoding process includes an image area information conversion process in step S2905 and a lossless encoding process in step S2907. The re-encoding process includes a decoding process in step S2915, an image area information conversion process in step S2917, and a re-encoding process in step S2919. The other steps are conditional branch and start and end steps, except for the change in the image area information change processing in S2913.
[0242]
First, from step 2901, encoding processing of image area information is started. In the next step 2903, it is detected whether or not the input of the image area information for one page of the image (one image) is completed. If area information is input, the image area information conversion process in step S2905 is performed.
[0243]
In the initial state where the re-encoding process has not been started yet, nothing is performed in the image area conversion process, and the input image area information is directly encoded in the lossless encoding process of the next step S2907.
[0244]
In the next step S2909, it is determined whether or not the re-encoding process is being performed. If the re-encoding process is being performed, the re-encoding process including steps S2915 to S2919 is performed. In step S2911, it is determined whether the total data amount (total code amount) of the image data and image area information encoded by the image / image area encoding control unit has exceeded the set value.
[0245]
If not, the process returns to step S2903, and the encoding process is repeated. If it is over, the processing content in the image area information conversion process is changed. With this change, the contents of the image area conversion processing in steps S2905 and S2917 change. Specifically, in the initial state, all the input image area flag data is encoded without invalidating even one bit. That is, nothing has been done in the image area conversion process, but after changing the processing contents, at least the 1-bit flag data in the image area information is discarded or replaced with a fixed value in the image area conversion process. Do. Thereafter, every time the processing content is changed, the number of bits of the image area flag to be discarded or replaced with a fixed value is increased.
[0246]
After changing the image area information conversion processing content, re-encoding processing is performed. In the re-encoding process, in step S2915, the already encoded image area information is decoded and returned to the data before encoding. In next step S2917, image area information conversion processing is performed, and a part of the image area information is discarded or replaced with a fixed value. In the next step S2919, the converted image area information is losslessly encoded again.
[0247]
When the re-encoding process is completed, the process returns to step S2903, and if there is input of image area information, it is encoded. In the image / image area encoding control unit, when the sum of the code amount of the image data and the image area data exceeds the set value even once, the content of the image area information conversion process is changed, and the image area information conversion process in step S2905 After a part of the image area flag data is replaced with waste medicine or a fixed value, lossless encoding is performed in step S2907.
[0248]
If the re-encoding process continues even after all the image area information has been input, the process proceeds from step S2903 to step S2921, where it is determined that the re-encoding process is being performed, and step S2915, The re-encoding process consisting of S2919 is performed.
[0249]
If all the input of the image area information has been completed and the re-encoding process has not been performed, the process proceeds to step S2923 to end the image area information encoding process.
[0250]
Next, specific processing in this embodiment when 6-bit data “000000” is added to 2-bit image area flag data per pixel to 8 bits, and then Packbits encoding is performed as a lossless code The contents will be described in more detail with reference to FIG.
[0251]
As shown in FIG. 30A, the 8-bit data before Packbits encoding is all 0 in the upper 6 bits, and a flag indicating whether the corresponding pixel data is a character part or not in the upper side of the lower 2 bits. On the lower side, flag data representing a chromatic color or an achromatic color is stored. Therefore, the values that the 8-bit data can take are values of 0 or more and 3 or less.
[0252]
It is assumed that the 8-bit data is output from the image area information generation unit 2801 in units of pixels. As specific output data, consider the data shown in FIG.
[0253]
When this is Packbits encoded, it is compressed into the 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 a sign bit (MSB) of the length information. Each data after compression is 8 bits (1 byte) as in FIG. The maximum value that can be represented by 1-byte length information is about 128, which is half of 255. If the length information is less than that, one set of length information followed by flag data group of image area information Encoding is possible, and if it exceeds that, it is divided into a plurality of sets of length information + image area flag data group.
[0254]
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.
[0255]
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. 9C, only the positive length information is underlined so that the length information and the image area flag data can be easily distinguished.
[0256]
“−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.
[0257]
A description will be given of how the compressed data is re-encoded by the lossless code re-encoding unit 2815 with reference to FIGS. Here, an example is shown in which all the chromatic colors are fixed by fixing the chromatic / achromatic color flag to “1” in the re-encoding process.
[0258]
The encoded image area data is once decoded and returned to the data of FIG. 30B, and then the flag data is replaced and converted to the data of FIG. Then, the encoded data shown in FIG. 5E 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.
[0259]
In spite of performing the re-encoding process, the count value of the total code amount that is the sum of the code amounts of the image data and the image area data is set in the register in the image / image area encoding control unit 2819. When the total target value of the code amount of the image data and the image area data is exceeded again, if the re-encoding process is completed, 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.
[0260]
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.
[0261]
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.
[0262]
Since the Packbits encoding circuit, decoding circuit, and data conversion circuit are well-known techniques, descriptions of individual circuit configurations are omitted.
[0263]
In the above description, the number of significant bits of the image area information 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.
[0264]
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.
[0265]
The two types of encoded data are multiplexed when they are output to a network lateral device, an image output device, a mass storage device, or the like connected to the outside. In consideration of the multiplexing, the units for encoding the two types of data are matched to the same size, and the encoded data generated by encoding one unit is managed and stored as one packet or file. . 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.
[0266]
Since the two encoding processes are controlled independently, the image data compression encoding processing unit may have another configuration. Therefore, even if units 2801 and 2819 for performing lossless encoding processing of the image area flag data are added to the configuration of FIG. 2, the same processing can be performed. The configuration is shown in FIG. 31. The operations of the units 2801 to 2819 are exactly the same as those of FIG. 28, and the operation of the image data compression portion is also the same as the operation of FIG.
[0267]
<Sixth Embodiment>
In the second embodiment, a description will be given of a processing method capable of finely controlling the amount of code by increasing the number of re-encoding processes even when the number of bits of image area information is the same as that in the first embodiment. The configuration of this embodiment is also the same as that of the fifth embodiment, and the difference is the image area flag data degeneration method in the lossless encoding unit 2805 and the lossless code re-encoding unit 2815.
[0268]
In the first embodiment, the image area information is replaced with a fixed value bit by bit, that is, data is degenerated bit by bit. In the present embodiment, the number of states is degenerated. 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, and the data amount (code amount) after encoding is reduced finely.
[0269]
When the fifth embodiment is expressed using the term number of states, it can be said that the number of states is reduced to half each time image area information is re-encoded.
[0270]
While the fifth embodiment reduces the number of states by half in one re-encoding process, the sixth embodiment reduces the number of states one by one, so that the code amount can be reduced finely. Of course.
[0271]
The processing results of the present embodiment are shown in FIGS. 32B, 32C, 32D, and 32E, and will be described.
[0272]
The same figure (a) is the same data as the image area flag data shown in (b) in FIG. The four states are listed again as follows.
[0273]
(1) Chromatic character line drawing (corresponding to data “3”)
(2) Achromatic character line drawing (corresponding to data “2”)
(3) Chromatic color non-character line drawing part (halftone part) (corresponding to data “1”, also called chromatic color image part)
(4) Achromatic non-character line drawing part (halftone part) (corresponding to data “0”, also referred to as achromatic image part)
In the present embodiment, in the first re-encoding process, two states of (3) a chromatic non-character portion and (4) an achromatic non-character portion are combined into one state among the four states. (3 ′) Reduce to a non-character part.
[0274]
As a result, the following three states are obtained.
[0275]
(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 degeneration is changed to the data shown in FIG. When this is encoded by Packbits, the encoded data shown in FIG. It can be seen that the encoded data before re-encoding is somewhat smaller in code amount than in FIG.
[0276]
In the second re-encoding process, the two states of (1) the chromatic color character portion and (2) the achromatic color character portion are merged to be reduced to one state (1 ′) character portion. As a result, the following two states are obtained.
[0277]
(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 degradation is changed to the data shown in FIG. This data is the same as the data in FIG. FIG. 32 (e), which is encoded data obtained by encoding Pac kbit s, is naturally the same encoded data as FIG. 30 (e).
[0278]
In the fifth embodiment, the 15-byte data before re-encoding is reduced to 6 bytes by one re-encoding, but in the sixth embodiment, it is reduced to 11 bytes by the first re-encoding. In the second re-encoding, it is finally reduced to 6 bytes. Eventually, in the sixth embodiment, since it is possible to obtain a code amount that changes finely and cannot be obtained in the fifth embodiment, compressed data of an image area flag close to the target code amount can be obtained. .
[0279]
<Seventh Embodiment>
In the fifth embodiment, the encoding control unit 2813 and the encoding sequence control unit 108 send the count values from the fourth counter 2811 and the first counter 107 to the sixth counter 2809, respectively. 6 counter 2809 adds up the count of image data encoding and image area data encoding, and sends the count value to image / image area encoding control section 2819. Then, with respect to the total target value of the image data and the image area data held in the register in the image / image area encoding control unit 2819, the total count value of the code amount of the image data and the image area data is calculated as follows. The configuration has been described in which it is determined whether or not the target value has been exceeded, and when the target value is exceeded, a control signal is output to the encoding control unit 1713 and the encoding sequence control unit 108 so as to perform re-encoding processing.
[0280]
In the seventh embodiment, with reference to the count values of the fourth counter 2811, the first counter 107, and the sixth counter 2809, re-encoding processing of image data and image area data is performed independently. In the following, an embodiment will be described.
[0281]
The register in the image / image area encoding control unit 1719 holds the total target value (target code amount) of the image data and the image area information, and the image data and image area information are stored from the sixth counter 2809. The total count value of the code amount is sent. When the total code amount exceeds the target value in the register, the image / image area encoding control unit 2819 performs re-encoding processing on the encoding control unit 2813 and the encoding sequence control unit 108. A control signal is output.
[0282]
The fact that the target value in the image / image area encoding control unit 2819 has been exceeded means that the target code amount of the image data and the image data held in the registers in the encoding sequence control unit 108 and the encoding control unit 2813, respectively. This means that at least one of the image data and the image area information has exceeded the target code amount of the area information (there may be both cases).
[0283]
Receiving the re-encoding control signal from the image / image area encoding control unit 2819, the encoding control unit 2813 and the encoding sequence control unit 108 indicate that the count values of the first counter 107 and the fourth counter 2811 are encoded. The image data code amount target value and image area data code amount target value, which are held in the registers in the encoding control unit 2813 and the encoding sequence control unit 108, are determined to determine whether they are over. If it is over, the control signal for the re-encoding process described above is output and the re-encoding process is performed.
[0284]
For example, the code amount of the image area data does not exceed the target value in the encoding control unit 2813, and the code amount of the image data exceeds the target value in the encoding sequence control unit 108, As a result, when the target value of the image / image area encoding control unit 1719 is exceeded, the encoding control unit 1713 does not output a re-encoding control signal for the image area data, and the encoding sequence control unit Reference numeral 108 outputs a control signal for re-encoding processing on the image data.
[0285]
As a result, even if the total target value of image data and image area data is exceeded and re-encoding processing is performed, re-encoding processing is performed only on the dominant data as a factor exceeding the target value. Thus, each target value is not exceeded. For example, in the above-described example, it is not necessary to re-encode the image area data, so it is possible to avoid useless image quality degradation.
[0286]
<Eighth Embodiment>
In the fifth embodiment, the count values from the fourth counter 2811 and the first counter 107 are sent from the encoding control unit 2813 and the encoding sequence control unit 108 to the sixth counter 2809, respectively. The sixth counter 2809 sums the encoding amount (count value) of image data encoding and image area information encoding, and sends the total value to the image / image area encoding control unit 1719. Then, for the total target value of the image data and the image area information held in the register in the image / image area encoding control unit 2819, the total value of the code amounts of the image data and the image area information is the target value. When the signal exceeds the value, the encoding unit 2813 (including the lossless code re-encoding unit 2807 as a result) and the control signal for performing re-encoding processing on the encoding sequence control unit 108 The configuration for outputting is described.
[0287]
In such a configuration, a re-encoding process control signal for the image / image area encoding control unit 2819 to the encoding control unit 2813 and the encoding sequence control unit 108 may be alternately output.
[0288]
  When the target value held in the register in the image / image area encoding control unit 2819 is exceeded, first, the encoding sequence control unit 108 isRe-encodingA processing instruction request is issued and re-encoding is performed. If the target value held in the register in the image area encoding control unit 1719 is exceeded even after performing this re-encoding, the encoding control unit 2813 (lossless encoding unit 2805) is next executed. The lossless code re-encoding unit 2807) outputs a request signal to perform re-encoding processing.
[0289]
Thereafter, every time it is determined that the target value is exceeded, the compression rate of re-encoding is alternately increased.
[0290]
As a result, it is possible to suppress encoding with an excessively high compression rate.
[0291]
The processes of the first to eighth 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 diagram shown in FIG. 1 and the first to eighth 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.
[0292]
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.
[0293]
【The invention's effect】
As described above, according to the present invention, it is possible to perform encoding that fits in a target size without re-inputting image area information of a multilevel image.
[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 showing another configuration in the first embodiment.
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 block configuration diagram of an apparatus according to a third embodiment.
FIG. 23 is a flowchart showing a processing procedure in the third embodiment.
24 is a diagram illustrating encoded data of a lossless code and encoded data after re-encoding in the third embodiment. FIG.
FIG. 25 is a diagram showing another configuration in the third embodiment.
FIG. 26 is a diagram illustrating encoded data after re-encoding of the lossless code and encoded data after re-encoding according to the fourth embodiment.
FIG. 27 is a diagram illustrating a data flow and memory contents in an encoding phase in an initial state according to the third embodiment.
FIG. 28 is a block configuration diagram of an apparatus according to a fifth embodiment.
FIG. 29 is a flowchart illustrating a processing procedure in the fifth embodiment.
FIG. 30 is a diagram illustrating encoded data of a lossless code and encoded data after re-encoding in the fifth embodiment.
FIG. 31 is a diagram showing another configuration in the fifth embodiment.
FIG. 32 is a diagram illustrating encoded data after re-encoding of lossless code and encoded data after re-encoding in the sixth embodiment.
FIG. 33 is a diagram illustrating a data flow and memory contents in an encoding phase in an initial state according to the fifth embodiment.

Claims (8)

An image processing method for inputting image area information for each pixel of multi-value image data and compressing and encoding the image area information,
A first encoding step for lossless encoding of the input image area information;
A second encoding step of expanding the lossless encoded data in the first encoding step and lossless encoding again;
Monitoring the amount of encoded data obtained in the first encoding step, and determining whether or not the amount of encoded data satisfies a predetermined standard,
When it is determined by the monitoring step that the encoded data amount satisfies a predetermined standard, the first encoding step converts the image area information that is subsequently input according to a predetermined condition, and then performs lossless encoding. In the second encoding step, the image area information represented by the encoded data already encoded by the first encoding means is converted in accordance with a predetermined condition and then re-encoded. . And a third encoding step for encoding the multi-value image data.
The monitoring step monitors the total of the encoded data amount obtained in the third encoding step and the encoded data amount obtained in the first encoding step, and determines the predetermined reference based on the total data amount. The image processing method according to claim 1, wherein it is determined whether or not the image is satisfied. And a third encoding step for encoding the multi-value image data.
The monitoring step monitors the total of the encoded data amount obtained in the third encoding step and the encoded data amount obtained in the first encoding step, and the total data amount and the first encoding step 2. The image processing method according to claim 1, wherein it is determined whether or not each of the encoded data amounts obtained in step 1 exceeds a target code amount, thereby determining whether or not the predetermined criterion is satisfied. An image processing apparatus that inputs image area information for each pixel of multi-value image data and compresses and encodes the image area information.
First encoding means for losslessly encoding the input image area information;
A second encoding means for decompressing the encoded data that has been losslessly encoded by the first encoding means and performing lossless encoding again;
Monitoring means for monitoring the amount of encoded data obtained by the first encoding means, and determining whether or not the amount of encoded data satisfies a predetermined standard;
When the monitoring unit determines that the encoded data amount satisfies a predetermined standard, the first encoding unit converts the image area information that is subsequently input according to a predetermined condition, and then performs lossless encoding. The second encoding means converts the image area information represented by the encoded data already encoded by the first encoding means according to a predetermined condition and re-encodes the image processing apparatus. . And further comprising third encoding means for encoding the multilevel image data.
The monitoring means monitors the sum of the encoded data amount obtained by the third encoding means and the encoded data amount obtained by the first encoding means, and determines the predetermined reference based on the total data amount. The image processing apparatus according to claim 4, wherein it is determined whether or not the condition is satisfied. And further comprising third encoding means for encoding the multilevel image data.
The monitoring means monitors the sum of the encoded data amount obtained by the third encoding means and the encoded data amount obtained by the first encoding means, and the total data amount and the first encoding means 5. The image processing apparatus according to claim 4, wherein it is determined whether or not each of the encoded data amounts obtained in step S1 exceeds a target code amount, thereby satisfying the predetermined criterion. . A computer program that functions as an image processing apparatus for inputting and compressing and encoding image area information for each pixel of multi-valued image data by being read and executed by a computer,
First encoding means for losslessly encoding the input image area information;
A second encoding means for decompressing the encoded data that has been losslessly encoded by the first encoding means and performing lossless encoding again;
Monitoring the amount of encoded data obtained by the first encoding means, and functioning as monitoring means for determining whether or not the amount of encoded data satisfies a predetermined standard;
When the monitoring unit determines that the encoded data amount satisfies a predetermined standard, the first encoding unit converts the image area information that is subsequently input according to a predetermined condition, and then performs lossless encoding. The second encoding unit converts the image area information represented by the encoded data already encoded by the first encoding unit according to a predetermined condition, and re-encodes the image area information.
A computer program characterized by the above. A storage medium storing the computer program according to claim 7.

Images