JP4065522B2 - Image processing apparatus and control method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a technique for encoding image data.
[0002]
[Prior art]
Conventionally, as a still image compression method, a JPEG method using discrete cosine transform (hereinafter abbreviated as DCT) and a method using Wavelet transform are often used. Since this type of encoding method is a variable-length encoding method, the code amount 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, when reading an original image with an image scanner, the code amount cannot be adjusted without pre-scanning, and there is a risk of memory over when used in a system that stores data in a limited memory.
[0004]
In order to prevent this, it is necessary to secure a sufficient memory capacity. However, the sizes of the input images are not always the same but may be different. Therefore, until now, it has been necessary to secure a memory having a capacity that can be adapted to the maximum size that can be input.
[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 in the image output unit and adjustment of the number of gradations in order to improve the appearance at the time of image output. By changing the type of ink that is used in the same black color, natural images that contain both chromatic and achromatic colors and black characters that are often found in document manuscripts can be seen as natural images, but characters are clear. Can be output.
[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 data can be stored in a predetermined memory capacity by using a known JPEG encoding method and gradually increasing the quantization step.
[0008]
On the other hand, 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. As an example of lossless encoding, Packbits and JBIG encoding methods are known.
[0009]
[Problems to be solved by the invention]
The present applicant has already proposed several techniques for compressing image data and image area information while inputting an image. According to such a proposal, the image data and the image area information are successfully suppressed within the target size. For example, when one code amount is sufficiently smaller than the target size, the remaining memory capacity is reduced to the other code. It has not been used effectively for storing structured data. That is, when the total size of the two types of code amounts is viewed, the total storable memory capacity has not been effectively used.
[0010]
The present invention has been made in view of such problems, and an object of the present invention is to provide a technique for effectively using a memory by making the total code amount of image data and image area information equal to or less than a target size.
[0011]
[Means for Solving the Problems]
  In order to solve this problem, for example, an image processing apparatus of the present invention has the following configuration. That is,
  An image processing apparatus that compresses and encodes image data and image area attribute data represented by a plurality of bits for each pixel of the image data,
  First image encoding means for compressing and encoding the input image data in accordance with an image compression parameter;
  Second image encoding means for decoding encoded data generated by the first image encoding means and recompressing and encoding according to the compression parameters for the image;
  First attribute encoding means for compressing and encoding the input image area attribute data in accordance with an image area compression parameter;
  Decoding the encoded data generated by the first attribute encoding means, the image area attribute of the bit specified by the compression parameter for the image area in the image area attribute data obtained by decoding, other Second attribute encoding means for converting to a value indicating the image area attribute and performing recompression encoding;
  During the compression encoding by the first image encoding unit and the first attribute encoding unit, the total code amount of the encoded data generated by each reaches a set amount. Monitoring means for determining whether or not,
  When the monitoring unit determines that the total code amount has reached the set amount, the data amount of the encoded data generated by the first image encoding unit and the first attribute encoding unit Based on the correlation of the data amount of the encoded data generated in step 1, the first and second image encoding means or the first and second attribute encoding means are used as compression parameter update targets. A determination means for determining whether to
  When the determination unit determines that the compression parameter update target is the first and second image encoding units, the compression parameter for the image of the first and second image encoding units is updated and the setting is performed. The image data input after it is determined that the amount has been reached is compressed and encoded by the first image encoding means in accordance with the compression parameters for the updated image, and before it is determined that the set amount has been reached For the encoded data generated by the first image encoding means, the second image encoding means performs recompression encoding according to the updated image compression parameters,
  When the determination unit determines the compression parameter change target to be the first and second attribute encoding units, updates the compression parameters for the image areas of the first and second attribute encoding units, The image area attribute data input after it is determined that the set amount has been reached is compression-encoded by the first attribute encoding means according to the updated image area compression parameters, and the set amount has been reached. Control for causing the second attribute encoding unit to perform recompression encoding on the encoded data generated by the first attribute encoding unit before the determination in accordance with the compression parameter for the updated image area With means,
  The determining means includes
  The ratio between the encoded data amount of the image data set in advance and the encoded data amount of the image area attribute data, the data amount of the encoded data generated by the first image encoding means, and the first attribute code First means for tentatively determining a compression parameter update target and a compression parameter based on a ratio of the amount of code data generated by the conversion means;
  A second means for calculating a recompression prediction time required when recompressing with the compression parameter update target and the compression parameter temporarily determined and a predicted arrival time for reaching the set amount again by the first means; Means of
  Recompression prediction time and prediction arrival time obtained by the second means
  Recompression predicted time <predicted arrival time
  If the above condition is satisfied, third means for final determination of the compression parameter change target and the compression parameter that are provisionally determined;
  When the condition is not satisfied, the image when it is assumed that compression encoding is performed by the provisional determination. The estimated code amount of the data and the estimated code amount of the image area attribute data are used as the data amount of the encoded data of the image data and the encoded data amount of the image area attribute data in the first means. A fourth means for repeating the third means;
  It is characterized by including.
[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 means for rendering a page description language into a raster image, or may be realized by reading an image file stored in a storage medium. May be received from the network.
[0015]
The encoding unit 102 encodes input image data. The encoding method uses a known JPEG encoding method, DCT transforms image data with 8 × 8 pixels, and quantization and Huffman encoding processing using a quantization step (determined by a compression parameter) described later. Is to do.
[0016]
The first memory control unit 103 and the second memory control unit 105 use the encoded data (the same encoded data) output from the encoding unit 102 as the first memory 104 and the second memory 106. It controls to store each. 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 it to the encoding sequence control unit 108 that controls the encoding sequence based on the count result. 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 encoded 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 to match the data amount in the first memory 104 (the input from the input unit 101 is continued). Further, the encoding unit 102 is controlled to perform encoding at a higher compression rate than before. Specifically, the quantization step for quantizing the DCT transform coefficient is set to be doubled.
[0019]
Although the quantization step is simply doubled here, in the case of a color image, one luminance signal (luminance data) generated when color conversion is performed and two color difference signals (color difference data). Therefore, finer control may be performed by assigning different quantization steps and alternately doubling each one.
[0020]
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 The first memory 104 stores a code generated by encoding data input after the discard operation shift.
[0021]
When the count value of the counter 107 reaches a certain set value, the encoding sequence control unit 108 transfers the second memory control unit 105 to the second memory 106 so far in parallel with the control. The stored encoded data is read, and a control signal is output so that the encoded data is output to the re-encoding unit 109 serving as encoded data conversion means.
[0022]
The re-encoding unit 109 decodes the input encoded data, performs re-quantization to reduce the amount of data, and then performs the encoding process again. The encoded data includes the first and second encoded data. The data is stored in the first and second memories 104 and 105 via the memory control units 103 and 105. At this time, the re-encoding quantization step in the re-encoding unit 109 is the same as the updated quantization step in the encoding unit 102. The code amount obtained by re-encoding by the re-encoding unit 109 is counted by the second counter 110.
[0023]
The second memory control unit detects whether or not the re-encoding process of the re-encoding unit 109 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 re-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 is performed when the encoding sequence unit 108 receives a re-encoding completion notification from the second memory control unit 105. As a result of this addition, the first counter 107 holds a count value representing the total amount of data in the first memory 104. That is, at the time when the encoding process of the encoding unit 102 and re-encoding unit 109 for one screen (page) is completed, the counter value held by the first counter 107 after the addition is one screen. This represents the total amount of data generated when this apparatus encodes minutes (for one page) (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]
The detection of whether or not the count value of the first counter 107 has reached a certain setting value is repeated until the encoding process (encoding and re-encoding) of image data for one page input from the input unit 101 is completed. Thus, the encoding and re-encoding processes described above are executed under control according to the detection result obtained here.
[0027]
The above processing contents will be described in a more easy-to-understand manner as follows. The following is about monochrome image encoding.
[0028]
The image data input from the input unit 101 is compressed and encoded by the encoding unit 102 in accordance with the quantization parameter Q1 at the initial stage. The generated compressed code data is written into the first memory 104 and the second memory 106, respectively. At this time, the first counter 107 counts the amount of code data to be generated. When the compression encoding process is completed while the amount is less than or equal to the set amount, the data stored in the first memory 104 is externally stored. If there is a subsequent image (image of the next page), the counters 107 and 110 are reset and input.
[0029]
On the other hand, when the encoding sequence control unit 108 detects that the amount of encoded data to be generated has reached the set value while encoding a certain page, the data in the first memory 104 is discarded. Then, the quantization parameter Q2 at the next stage is set so that the compression rate becomes higher for the encoding unit 102, and the input of the image data is continued. At this time, the first counter 107 is reset. As a result, the image data input after it is determined that the set value has been reached is encoded at a higher compression rate. Also, the encoded data (data encoded with the quantization parameter Q1) before the encoded data amount reaches the set value is stored in the second memory 106. Therefore, this data is re-encoded by the re-encoding unit 109 and the result is stored in the first memory 104 and the second memory 106, respectively. The quantization parameter at the time of re-encoding by the re-encoding unit 109 is the same as the quantization parameter Q2 of the encoding unit 102 after the setting change. When the re-encoding for the previous encoded data stored in the second memory 106 is completed, the code amount is held in the second counter 110, so that it is added to the first counter 107.
[0030]
As a result, the first memory 104 and the second memory 106 store the encoded data compressed with the quantization parameter Q2 from the top of one page. When it is determined that the value of the counter 107 has reached the set value again during compression encoding with the quantization parameter Q2, the quantization parameter Q3 is re-established with the encoding unit 102 and the re-encoder to achieve a higher compression rate. The above processing is performed by setting in the encoding unit 109. When it is determined that the set value is reached even with the quantization parameter Q3, the quantization parameter is set to Q4.
[0031]
The quantization step is increased by m times (m> 1) (Q2 = Q1 × m, Q3 = Q2 × m, Q4 = Q3 × m,... (Not necessarily equal). When the quantization step is increased, the frequency component value at the time of DCT conversion can be expressed with a small value, that is, with a small number of bits, and thus the data amount can be reduced.
[0032]
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.
[0033]
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.
[0034]
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. .
[0035]
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.
[0036]
<< Encoding Phase >>
Encoding processing of image data for one page starts from initial setting of encoding parameters (step S301). Here, the quantization step Q1 to be applied to the encoding unit 102 is set based on 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).
[0037]
In step S303, the first counter 107 performs actual encoding processing (JPEG compression of the image in units of 8 × 8 pixels) and cumulatively counts the amount of encoded data to be output.
[0038]
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.
[0039]
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.
[0040]
<< 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 S309, the quantization parameter of the encoding unit 102 is changed to Q2.
[0041]
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.
[0042]
After changing the quantization step and the contents of the quantization operation, in step S311, the encoding process of the encoding unit 102 is resumed, 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.
[0043]
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 (when m = 2). 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.
[0044]
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.
[0045]
Steps S307 to 315 described above are processes performed in the encoding / recoding phase.
[0046]
<< 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.
[0047]
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.
[0048]
Therefore, by repeating the encoding phase, the encoding / re-encoding phase, and the transfer phase, a code in which one page of image data is finally compressed to a set code amount or less 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.
[0049]
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.
[0050]
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.
[0051]
When 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 to end the compression encoding process for the page, and then the compression process If there is image data to be processed, compression encoding processing of image data for the next one page is started (respective counters are reset and quantization parameters are set to initial values).
[0052]
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.
[0053]
The above is the operation, and is also the operation description of FIG.
[0054]
<Modification of memory storage method>
9 and 10 are diagrams showing modifications of the memory storing method shown in the conceptual diagrams of FIGS.
[0055]
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.
[0056]
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.
[0057]
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.
[0058]
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.
[0059]
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.
[0060]
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.
[0061]
<Second example>
Next, a second example (the configuration described so far is referred to as the first example) for performing a characteristic encoding process in the present invention will be described with reference to FIG.
[0062]
FIG. 2 is a block diagram of the image processing apparatus 200 in the second example.
[0063]
A significant difference from the image processing apparatus 100 in the first example 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 the second example, a known JPEG encoding method is used as the encoding method, image data is DCT-converted in units of 8 × 8 pixel blocks, and quantization and Huffman encoding processing using a quantization step described later is performed. Is to do.
[0064]
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 parameter in the first encoding unit 202 is Q1, and the quantization parameter of the second encoding unit 205 is Q2 (the Q2 quantization step is larger than the Q1 quantization step). .
[0065]
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.
[0066]
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. Furthermore, when the encoded data stored in the second memory 207 described later is transferred to the first memory 204, the count value of the second counter 210 is transferred to the first counter 208 at the same time.
[0067]
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 first memory 204.
[0068]
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 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.
[0069]
In short, since the count value of the second counter 210 represents the amount of encoded data stored in the second memory 207, the encoded data corresponding to the count value is directly used as the first value. It can be considered that the data has been copied to the counter and the first memory.
[0070]
Further, the encoding sequence control 209 outputs a control signal to the second encoding unit 205 so as to perform encoding so that encoded data is smaller than before. On the other hand, for the first encoding unit 202, the setting is changed so as to inherit the quantization parameter Q2 in the second encoding unit 205 until just before.
[0071]
For example, the quantization step in the second encoding unit 205 is switched to twice. As a result, the first encoding unit 202 performs encoding processing with a higher compression ratio in preparation for the next overflow using the second encoding unit 205 using a larger quantization step Q3. 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.
[0072]
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. For example, in the case of a color image, separate quantization steps are assigned to one luminance signal (luminance data) generated at the time of color conversion and two color difference signals (color difference data), and each one is doubled alternately. By making it, it becomes possible to make finer settings.
[0073]
Then, the encoding sequence control 209 reads out the encoded data already stored in the second memory 207 and sends a control signal to the re-encoding unit 211 to the memory control unit 206. The re-encoding unit 211 performs re-encoding processing of encoded data in the same manner as the re-encoding unit 109 in FIG.
[0074]
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.
[0075]
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.
[0076]
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.
[0077]
To summarize the above operations, the second encoding unit 205 performs encoding at a compression rate that is one higher than that of the first encoding unit 202. When the code amount generated by the first encoding unit 202 reaches the set amount, the quantization parameter of the first encoding unit 202 is set to be the same as that of the second encoding unit 205 immediately before. Also, the quantization parameter of the second encoding unit 205 is set to be a higher compression rate. Then, the data in the first memory 204 is discarded, the data stored in the second memory 207 is transferred to the first memory 204, and the value of the second counter 210 is transferred to the first counter 208. Write. Then, in order to re-encode the data in the second memory at a higher compression rate, the re-encoding unit 211 is made the same as the quantization parameter newly set in the second encoding unit 205. As a result, the data in the second memory 207 stores code data equivalent to the data compressed with the newly set quantization parameter from the top of the page.
[0078]
When there are two encoding units as described with reference to FIG. 2, the image data for one page is encoded based on the flowchart shown in FIG. Note that the description of FIG. 12 is mostly similar to FIG. 8, which is a flowchart in the case of one encoding unit, and those skilled in the art will fully understand the features of the second example from the above description. Since it will be possible, the process will be described in three phases as in the case of one encoder, and the points different from FIG. 8 will be mainly described.
[0079]
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).
[0080]
In the initial setting of the encoding parameter in step S301, the quantization parameter Q1 is set in the first encoding unit 202, and the quantization parameter Q2 is set in the second encoding unit 205. However, the quantization step represented by the quantization parameter Q2 is larger than Q1.
[0081]
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.
[0082]
In order to increase the compression rate of the encoded data stored in the first memory 204 in a stepwise manner, the encoded data stored first stores data encoded with the quantization parameter Q1 having the lowest compression rate. The encoded data stored in the second memory stores data encoded with the quantization parameter Q2.
[0083]
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, the appropriate second candidate encoded data that does not exceed the upper limit value is quickly stored in the first memory 207. Can be stored. This is the greatest advantage of applying FIG. 2 with two encoders over FIG.
[0084]
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.
[0085]
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. The parameters 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 rate encoded data, the re-encoding unit 211 performs a re-encoding process (S313) so that data encoded using the quantization parameter Q3 is obtained, and the re-encoded data is 2 is stored again in the second memory 207.
[0086]
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.
[0087]
Further, when there are two encoding units as in the second example, as shown in FIG. 15, a situation in which encoded data and re-encoded data are mixedly stored in the second memory 207. Occurs. 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.
[0088]
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)) Need 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.
[0089]
The state of the encoding phase shown in FIG. 16 is the encoding phase in the initial state (FIG. 13) except that the method of mixing the quantization parameter 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.
[0090]
Since the arrangement order of the transfer phase and the encoding / re-encoding phase is opposite to that of the first example, the input end detection of one page of image data performed after the transfer process in FIG. S805) is 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.
[0091]
In the first and second examples described above, the first memory and the second memory have been described as physically separate memories. This is because it is advantageous that the accesses to the two memories are independent. 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.
[0092]
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.
[0093]
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.
[0094]
When the encoded data is stored in a file format or a packet format, the information transferred between the memory control units is slightly increased, and it is necessary to transfer the management table information related to the encoded data. Nevertheless, it is more efficient than transferring encoded data.
[0095]
<Third Example (Example in which Image Area Information Compression Function is Added to First Example)>
In the first and second examples, image data is encoded by the JPEG method and only the JPEG code is stored. FIG. 17 shows a configuration of an image processing apparatus that performs lossless encoding of image area information in parallel with this and stores the lossless code. This figure is obtained by adding an image area information processing system to the basic configuration shown in FIG. 1, and will be described below. However, the same functional blocks as those in the configuration of FIG.
[0096]
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. .
[0097]
On the other hand, the image data is sent to the image area information generation unit 1701 to generate the above-described image area information. In the case of a scanner input image, image area information is generated based only on the image data, but in the case of an image in which a page description language (PDL) is developed and drawn, the image area information is also generated with reference to the PDL information. 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.
[0098]
However, in order to simplify the description in the embodiment, the image area information includes 1 bit for distinguishing chromatic / achromatic color and 1 bit for distinguishing a character line image / halftone image for each pixel. And If the input image data is RGB format data, the chromatic / achromatic distinction is determined as an achromatic color when the values of the respective color components are substantially equal to each other, and as a chromatic color otherwise. Further, when the density (or luminance) of the pixel of interest changes sharply with respect to adjacent pixels (changes above a preset threshold value), it is determined that the edge of the character / line image is changed. If it is gentle, it can be realized by judging as a halftone image. The data that the image area information can take are binary representations of 00, 01, 10, and 11 (0 to 3 in decimal number).
[0099]
The generated image area information is the same size as the data to be encoded together in the encoding unit 102 in the blocking unit 1703 (since it was 8 × 8 in the first example, 8 × 8 Block).
[0100]
Multi-value compression such as JPEG used for image data compression is inefficient and lossy compression for use in compression of image area information that is a collection of binary data. For compression of the image area information, run length encoding such as JBIG or PackBits which is lossless compression is used, and the lossless encoding unit 1705 performs lossless encoding of the image area information.
[0101]
The encoded image area information is stored in the first memory 104 via the first memory control unit 103, and the same data is also stored in the second memory 106 via the memory control unit 105. At the same time, the fourth counter 1707 counts the amount of code output from the lossless encoding unit, and sends the count value to the lossless encoding control unit 1709.
[0102]
When a target value is set in the register in the lossless encoding control unit 1709 and the code amount exceeds the target value, the encoded data already stored in the first memory 104 (the encoded data of the image area information) A control signal is output to the first memory control unit 103 so as to be discarded. The method of discarding is the same as the method of discarding the encoded data of the image data. Subsequently, the lossless encoding control unit 1709 reads the encoded image area data from the second memory 106 and sends the data to the lossless code re-encoding unit 1711, so that the control signal is sent to the second memory control unit 105. Is output.
[0103]
That is, the lossless encoding 1705 and the lossless code re-encoding unit 1711 are similar to the case where the encoding unit 102 and the re-encoding unit 109 perform the compression process according to the instruction information (compression parameter) from the encoding sequence unit 108. The image area information is compressed in accordance with the compression parameter (parameter for determining the compression rate) from the lossless encoding control unit 1709.
[0104]
When the lossless code re-encoding unit 1709 receives the encoded data, the lossless code re-encoding unit 1709 performs lossless encoding again after discarding or replacing a part of the plurality of attribute flag data with a fixed value. As will be described later, 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 second memory 106 and also in the first memory 104. The code amount after re-encoding is counted by a fifth counter 1713.
[0105]
On the other hand, the lossless encoding control unit 1709 includes an image area included in the lossless encoding unit 1705 to encode attribute flag data whose amount of information has been reduced in the lossless code re-encoding unit 1711 and attribute flag data having the same information entropy. A control signal is sent to the information conversion processing unit so that part of the attribute flag is discarded or replaced with a fixed value, and the encoding process is continued. However, the encoded data is stored only in the second memory. At the same time, a control signal is also sent to the fourth counter 1711 to reset the value that has been counted and held so far, and the code generated by encoding processing after the content of the image area information conversion processing has been changed Let the amount count anew.
[0106]
When there is no encoded data of the image area information to be re-encoded and the re-encoding process is completed, the encoded data stored only in the second memory is transferred and stored also in the first memory. At the same time, the count value of the fifth counter 1713 is transferred to the fourth counter 1707 and added. Accordingly, the counter 1711 counts the total code amount of the lossless encoded data after the content of the image area information conversion process is changed, and the corresponding encoded data is stored in each of the first and second memories. Stored state. This state is almost the same as when only the initial lossless encoding process is performed. Therefore, thereafter, the encoded data output from the lossless encoding unit 1705 is stored in both the first and second memories, and the state returns to the same state as the initial state in which the lossless encoding process is performed. The code amount is monitored.
[0107]
Every time the count value of the fourth counter exceeds the target value set in the register in the encoding control unit 1709, the attribute flag is discarded or the attribute flag to be replaced with a fixed value is increased, so that the code amount of the image area data is increased. It can be reduced step by step, and the code amount of the image area data can be kept within the target value.
[0108]
Next, a flowchart showing the processing contents of the image processing apparatus of FIG. 17 is shown in FIG. As described above, the processing of the image processing apparatus is basically the same as the method for controlling the code amount of the image data in the configuration of FIG. 1, and the contents of the individual processing are slightly different. The differences are listed below.
(1) Encoding process and lossless encoding process
(2) Change of quantization step and change of image area information conversion process
(3) Re-encoding process and reversible code re-encoding process
The flowchart of FIG. 18 reflects the difference in the above processing in the flowchart of FIG. The processing in steps S303, S309, S311, and S313 in FIG. 8 is replaced with the processing in steps S1703, S1709, S1711, and S1713 in FIG. In the initial setting of the encoding parameter, the upper limit value of the lossless encoded data amount determined by the image size is set in a register in the lossless encoding control unit, and the contents of the image area information conversion process are reset to the initial state. The rest is the same as the flowchart of FIG.
[0109]
Next, 6-bit data “000000” is added to 2-bit image area information per pixel to make it 8 bits (generally because the processing is efficient with 8 bits in a computer), and then Packbits coding as a lossless code The specific processing contents when performing the above will be described in more detail with reference to FIG.
[0110]
As shown in FIG. 19A, the 8-bit data before Packbits encoding is 0 in all 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. It is assumed that flag data representing a chromatic color or an achromatic color is included in the lower side. Therefore, the values that the 8-bit data can take are values of 0 or more and 3 or less. Note that the characteristics of the image area are determined by each bit being 0 or 1 as described above and have characteristics as a flag. Therefore, the image area information is expressed as an image area flag or image area flag data in the following. I will do it.
[0111]
It is assumed that the 8-bit data is output from the image area information generation unit 1701 in units of pixels. As specific output data, consider the data shown in FIG.
[0112]
When this is encoded by Packbits, it is compressed into data shown in FIG. In the compressed data, a negative value represents the number of continuous data, and a non-continuous data number represents a positive value. These are length information, and it is possible to determine whether continuous data continues or non-continuous data continues from the sign bit of the length information. Each data after compression is 8 bits (1 byte) as in FIG. The maximum value that can be represented with 1-byte length information is about 128, which is half of 255. If the length information is less than that, it is encoded with a set of length information and the image area flag data group that follows. If it exceeds that, it is divided into a plurality of sets of length information + image area flag data group and encoded.
[0113]
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.
[0114]
The next data “4” is also length information, but this time is a positive value, indicating that four non-consecutive data continue. Therefore, the four data “2, 3, 2, 3” following the “4” represent discontinuous data. In FIG. 19C, only the positive length information is underlined so that the length information and the image area flag data can be easily distinguished.
[0115]
“−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 indicates that 6 image area flag data “0” are continuous.
[0116]
FIGS. 19D and 19E show how the compressed data is re-encoded by the lossless code re-encoding unit 1715 (which is executed when the set target value is reached). It explains using. Here, in the re-encoding process, the chromatic color / achromatic color flag is fixed to “1” to make all chromatic colors.
[0117]
The encoded image area data is once decoded and returned to the data of FIG. 19B, and then the flag data is replaced and converted to the data of FIG. 19D. Then, the encoded data shown in FIG. 19E is obtained by performing Packbits encoding on the converted data again. It can be seen that the encoded data of 15 bytes before re-encoding is reduced to 6 bytes after re-encoding.
[0118]
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.
[0119]
In the new re-encoding process, the remaining 1-bit image area flag is also replaced with “1” (indicating halftone). 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.
[0120]
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.
[0121]
The Packbits encoding circuit, decoding circuit, and data conversion circuit are known techniques, and the description of the individual circuit configuration is omitted.
[0122]
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.
[0123]
Furthermore, if a method for reducing the number of states is used, the amount of codes can be further controlled in multiple stages. For example, in a 2-bit image area flag, four states can be represented, but this is reduced to 3 states by the first re-encoding process and reduced to 2 states by the second re-encoding process. The information entropy before encoding is reduced little by little, and the data amount (code amount) after encoding is reduced finely.
[0124]
If the process of replacing the flag data described above with a fixed value bit by bit is expressed using the term number of states, it can be said that the number of states is reduced by half each time the image area flag data is re-encoded.
[0125]
Naturally, the amount of code can be reduced more finely by reducing the number of states by one than by reducing the number of states by half in one re-encoding process.
[0126]
The processing results when the number of states is reduced by one are shown in FIGS. 20B, 20C, 20D, and 20E, which will be described. FIG. 20A shows the same 2-bit 4-state data as the image area flag data shown in FIG. 19B. The four states are listed again as follows.
(1) Chromatic character part (corresponding to data “3”)
(2) Achromatic character part (corresponding to data “2”)
(3) Chromatic non-character part (corresponds to data “1”, also called chromatic image part)
(4) Achromatic non-character part (corresponding to data “0”, also called achromatic image part)
In the first re-encoding process, two states, (3) chromatic non-character part and (4) achromatic non-character part, are combined into one state (3 ′) Reduce to character. As a result, the following three states are obtained.
(1) Chromatic character part
(2) Achromatic character part,
(3 ') Non-character part
Specifically, the above state is degenerated by replacing data “0” with “1”. The data after the state degradation is changed to the data shown in FIG. When this is Packbits encoded, the encoded data shown in FIG. It can be seen that the code amount is somewhat smaller than that of the encoded data before re-encoding in FIG.
[0127]
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 degenerate the above state. The data after the state degeneration is changed to the data shown in FIG. This data is the same as the data in FIG. The encoded data obtained by packing this into Packbits FIG. 20 (e) is naturally the same encoded data as FIG. 19 (e).
[0128]
When the number of states is reduced by one, the 15-byte data before re-encoding is reduced to 11 bytes by the first re-encoding, and finally reduced to 6 bytes by the second re-encoding. Since it is possible to obtain a code amount that changes finely and decreases in this way, it is possible to obtain compressed data of an image area flag that is close to the target code amount.
[0129]
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.
The encoded two types of data are multiplexed when output to a network device, an image output device, a mass storage device, or the like connected to the outside. Considering the multiplexing, the unit for encoding the two types of data is matched to the same size as described above, and the encoded data generated by encoding one unit is stored in one packet or file. Manage and store as When multiplexing, two types of packet data having the same image position are connected in the order of, for example, image data and image area data to form one packet and output to the outside.
[0130]
<Fourth Example (Example in which Image Area Information Compression Function is Added to Second Example)>
FIG. 21 shows an image processing apparatus in which image area information is reversibly encoded in parallel with the image data encoding process and the lossless code is also stored. This figure is obtained by adding an image area information processing system to the basic configuration shown in FIG. 2, and will be described below. However, the functional blocks used in FIG. 2 and FIG. 17 are used in the figure, and the same reference numerals are given to the blocks, and description thereof is omitted.
[0131]
In the image processing apparatus of FIG. 21, two types of image area information having different information entropy are losslessly encoded by two encoding units, similarly to the image data compression encoding process in the configuration of FIG. The two encoding units are a first lossless encoding unit 1705 and a second lossless encoding unit 2106. The second lossless transformation unit 2106 added here encodes the image area information with lower entropy than the first lossless coding unit.
[0132]
The other additional blocks are only the sixth counter 2108 that counts the code amount output from the second lossless transform unit 2106.
[0133]
In FIG. 21, a block for compressing and encoding image data and a block for reversibly encoding image area information have the following correspondence.
(1) First and second encoding units and first and second lossless encoding units
(2) First, second and third counters and fourth, sixth and fifth counters
(3) Re-encoding unit and lossless code re-encoding unit
(4) Encoding sequence control unit and lossless encoding control unit
Image data is compression-encoded using the former blocks of the above items, and image area information is losslessly encoded using the latter blocks. The two encoding processes are independently controlled in almost the same manner, and each data is compressed to a target code amount or less.
[0134]
The amount of code for image data is gradually reduced by changing the quantization step, but image area information can be reduced by reducing the number of states of the flag data of the image area information before lossless encoding to lower entropy. The code amount after lossless encoding is reduced.
[0135]
In the initial state, the first lossless encoding unit 1705 encodes the entire image area information for each pixel, but the second lossless encoding unit 2106 sets the number of states of the flag data of the image area information as described above. Lossless encoding is performed after reduction by the information conversion process.
[0136]
When the code amount output from the first lossless encoding unit exceeds the target value (or reaches the target value), the lossless code stored in the first memory 104 is discarded, and the second memory 106 The lossless code stored in the first lossless code is transferred to the first memory, and the image area information conversion processing performed by the second lossless encoding unit is taken over by the first lossless encoding, and is transferred to the first memory. The encoded data is stored after the transferred lossless code.
[0137]
The second lossless encoding unit performs image area information conversion processing that further reduces the number of states of the flag data than before, and performs lossless encoding. By doing so, the first lossless encoding unit generates a lossless code with a smaller code amount and stores it in the second memory.
[0138]
The lossless code in the second memory that has already been encoded by the second lossless encoding unit, that is, the lossless code transferred to the first memory is decoded by the lossless code re-encoding unit 1711, The reversible code re-encoding unit performs image area information conversion processing so as to have the same number of states as the image area information conversion processing performed by the lossless encoding unit, performs lossless encoding again, and writes back to the second memory. As described above, also in the configuration shown in FIG. 21, it is possible to control the code amount by performing the image area information encoding process by the same method as the image data compression encoding process.
[0139]
Therefore, the flowchart of the above-described process can be used as it is by changing only a part of the expression of the flowchart for compressing and encoding the image data shown in FIG. Similar to the change from the flowchart of FIG. 8 to the flowchart of FIG. 18, the following three points are changed.
(1) Encoding process → Lossless encoding process
(2) Change quantization step → Change image area information conversion process
(3) Re-encoding process → Lossless code re-encoding process
FIG. 22 shows a flowchart in which the above three points are changed. The four processing contents of steps S2103, S2109, S2111, and S2113 are changed as described above.
[0140]
Since the compression coding process of image data and the coding process of image area information are performed in parallel and controlled independently, the image processing apparatus shown in FIG. 21 defines the processing flow according to the two flowcharts of FIGS. I can do it.
[0141]
<First Embodiment>
In the above, the example used as the premise of embodiment of this invention was demonstrated. In the first embodiment, a configuration and a control method are provided for overcoming the problems to be solved as described above with respect to the third example and the fourth example. In order to simplify the description, the description will be made here with respect to the configuration of FIG. 21 (fourth example). However, those skilled in the art can easily conceive what can be applied to the third example from the following description.
[0142]
In FIG. 21, the code amount is controlled independently by the encoding sequence control unit and the lossless encoding control unit so that each code amount of the image data and the image area information is equal to or less than each set code amount. Therefore, if each control is performed reliably, the total code amount is surely within the sum of the two set code amounts.
[0143]
However, when one of the code amounts is significantly small, the entire code amount is over-compressed. When one of the code amounts is surely smaller than the set code amount, in order to effectively use the remaining code storage memory, it is necessary to comprehensively control by looking at the two code amounts.
[0144]
Therefore, in the first embodiment, as shown in FIG. 23, both the lossy encoded code amount and the lossless encoded code amount are input to the encoding sequence control unit 209.
[0145]
The encoding processing flow of the first embodiment is obtained by replacing a part of the flowchart shown in FIG. 12 (S305, S307, S309, S317) with the flowchart of FIG. However, it is assumed that the encoding processing in steps S303 and S311 performs both lossless encoding and lossy encoding in parallel.
[0146]
A total sum W of two types of code amounts (code amount in the first encoding unit 202 and code amount in the first lossless encoding unit 1705) obtained by encoding the image information input in step S2401 is calculated.
[0147]
In step S2403, the total sum W is compared with a set code amount T set as an upper limit of the total code amount.
[0148]
In step S2405, the irreversible code amount (code amount of image data) is divided by the sum to obtain the ratio R of the irreversible code amount to the total code amount. In step S2407, the ratio is compared with the set code ratio P. The set code ratio P is a threshold value serving as a reference value for the ratio of the irreversible code amount to the total code amount.
[0149]
In order to effectively use the code storage memory with two types of codes, the total sum W of the two types of codes is calculated in step S2401, and whether or not the total sum W exceeds the set code amount T is determined in step S2403. To detect. Even if either one of the code amounts exceeds the corresponding set code amount, if the total sum W does not exceed the set code amount T, the encoding process is continued as it is. Therefore, if W> T is not satisfied, the process passes from S2405 to S2415 and proceeds to S2417, and the next block is encoded.
[0150]
However, when the total sum W exceeds the set code amount T, the entire code amount does not fall within the set code amount T unless at least one of the codes is re-encoded. Therefore, to determine which code is to be re-encoded, the ratio R of the lossy code amount to the total code amount is calculated in step S2405, and the ratio R is compared with the set code ratio P in step S2407. To do.
[0151]
When the ratio R is larger than the set code ratio P, the code amount of the irreversible code (JPEG) is larger than the reference, so the process proceeds to step S2409 and control is performed so as to start the re-encoding process of the irreversible code. . In the opposite case, the process moves to step S2411, and control is performed so as to start re-encoding processing of lossless codes (Packbits).
[0152]
In any case, in order to encode the uncompressed image information into a code having the same compression rate (setting) as the code after the re-encoding process, in step S2413 or step S2415, the compression condition of the corresponding encoding unit, etc. Then, the process proceeds to a loop process including the encoding process of S311 and the re-encoding process of S313 in FIG. The various determination processes are performed by the coding sequence control unit 209, and from here, the four coding units and the two memory control units are controlled.
[0153]
As described above, the two types of codes are not independently re-encoded, but the code having a larger code amount than the set ratio is re-executed when the total code amount W exceeds the set code amount T. By performing the encoding process, the number of re-encoding processes can be reduced and the code storage memory can be used effectively.
[0154]
The set code ratio P may not be the ratio of the irreversible code amount to the total code amount, but may be the ratio of the lossless code amount to the total code amount. The value calculated in step S2405 may not be the ratio of the irreversible code amount to the total code amount W, but may be a value obtained by dividing the irreversible code amount by the set code amount T.
[0155]
This value represents the occupancy ratio of the irreversible code amount in the code storage memory, but both values immediately after the total code amount W exceeds the set code amount T can be regarded as almost the same value. There is no significant difference. When the set code amount T is used, it is advantageous in terms of calculation speed if the reciprocal is obtained in advance and multiplied.
[0156]
Further, what is compared in step S2407 may be a ratio of two types of code amounts, for example, lossless code amount / lossy code amount. In this case, there is no problem if the set code ratio is also a value corresponding thereto.
[0157]
Further, when the ratio R of the lossy code amount at the time of overflow detection is not so different from the set code ratio P, it is one method to re-encode both codes simultaneously. In order to realize this, an absolute value of the difference between the two may be obtained and a step of detecting that it is smaller than the set threshold value may be added.
[0158]
In short, according to the technical idea of the present embodiment, the compression encoding target may be determined so that the correlation between the lossless code amount and the lossy code amount approaches a preset preferable correlation (balance). .
[0159]
Also in the configuration of FIG. 17, both the losslessly encoded code amount (the output of the first counter) and the losslessly encoded code amount (the output of the fourth counter) are used as the encoding sequence control unit 108. The code storage memory can be used effectively by performing the same control as described above.
[0160]
The configuration of FIG. 21 is more complicated than the configuration of FIG. 17, but as described so far, the configuration of FIG. 17 and the configuration of FIG. 21 are extremely related, and the possible control method in FIG. In addition, it can be easily analogized by those skilled in the art that this is also possible in FIG. In the following embodiment, the description will be limited to the configuration of FIG.
[0161]
The first embodiment has been described mainly based on the fourth example (FIG. 21). However, the third example may be based on the fourth example. If the third example is used as a base, the configuration will be as follows. That is,
An image processing method for compressing and encoding image data and image area information of the image data,
A first lossy compression encoding process for image data in which compression parameters can be changed;
A second irreversible compression encoding process for image data, the compression parameter of which can be changed, and compression-encoded with a compression parameter having a higher compression ratio than the first irreversible compression encoding process;
Decoding the code data compressed in the second lossy compression encoding step, and a third lossy compression encoding step for image data to be re-encoded;
A first lossless compression encoding process for image area information with variable compression parameters;
A second lossless compression encoding step for image area information, the compression parameters of which can be changed, and compression encoded with a compression parameter having a higher compression ratio than the first lossless compression encoding step;
A third lossless compression encoding step for image area information for decoding and re-encoding the code data compressed in the second lossless compression encoding step;
Whether or not the total code amount of the code amount generated by each of the first lossy compression encoding step and the first lossless compression step during compression encoding has reached a predetermined amount A code amount monitoring step for determining
When it is determined by the encoding amount monitoring step that the total code amount has reached the predetermined amount, the correlation between the code amount by the first lossy compression step and the code amount by the first lossless compression step A determination step for determining information on which compression parameters are to be changed based on the relationship;
A control step for controlling the first to third lossy compression steps and the first to third lossless compression steps with the contents determined in the determination step;
The control process is
When it is determined that the object whose compression parameter is changed by the determination step is image data,
Updating the compression parameters of the first and second lossy compression encoding processes;
For the first lossy compression encoding step, the second lossy compression encoding step is inherited and the compression process is continued.
For the third lossy compression encoding step, re-encode the image data compressed and encoded in the second lossy compression encoding step before it is determined that the predetermined amount has been reached,
When the determination step determines that the object whose compression parameter is to be changed is image area information,
Updating the compression parameters of the first and second lossless compression encoding steps;
For the first lossless compression encoding process, the compression process is continued by inheriting the second lossless compression encoding process,
For the third lossless compression encoding step, the image area information compression encoded in the second lossless compression encoding step before it is determined that the predetermined amount has been reached is re-encoded.
An image processing method.
[0162]
<Second Embodiment>
In the first embodiment, the re-encoding process is extremely fast, that is, re-encoding is performed before the total code amount W exceeds the set code amount T (W> T) in the re-encoding process for any setting. This is a very effective control method in the case where the digitization process is always finished.
[0163]
However, it is naturally possible that the code amount after the re-encoding process is hardly reduced. In this case, the time until the next overflow becomes very short, and it may be difficult to end the re-encoding process within the time limit.
[0164]
The second embodiment shows an example for solving such a problem. In order to simplify the explanation, this time, based on the configuration of FIG. 17, the total code amount W next exceeds the set code amount T while effectively using the storage memory as in the first embodiment. An example of realizing a control method in which the re-encoding process is always finished by (W> T) will be described.
[0165]
The configuration in the case where the second embodiment is applied to the configuration of FIG. 17 is, as described above, the lossy encoded code amount (output of the first counter) and the lossless encoded code amount (fourth). The output of both counters) is obtained by inputting both code amounts to the encoding sequence control unit 108. A block diagram is shown in FIG.
[0166]
The flowchart of FIG. 26 is inserted and executed before or after step S307 in FIG. 12, which is a flowchart representing the processing flow of the configuration of FIG. 2, which is originally a flowchart representing the processing flow of the configuration of FIG. .
[0167]
The processing flow of FIG. 26 will be briefly described below. If it is detected in step S305 (FIG. 3 or FIG. 12) that the code amount exceeds the set value, an encoding setting condition that provides a higher compression rate than before is determined as a setting candidate (S2601). The code amount at the time of re-encoding with the setting candidate is estimated (S2603), and the memory free space at that time and the shortest time from the predicted generated code amount at the setting candidate to the overflow are estimated (S2605). On the other hand, the re-encoding time is estimated based on statistics such as the number of symbols of the code to be re-encoded (S2607). If the estimated re-encoding time is longer than the estimated shortest time (S2609), there is no guarantee that the actual re-encoding process will be completed before the code amount exceeds the set value. The stage setting is updated, and a coding setting condition with a higher compression rate is set as a setting candidate (S2601). As the compression rate increases, the amount of code after the re-encoding process also greatly decreases, so the shortest time becomes longer. Therefore, when a certain encoding setting condition is reached, the relationship of estimated shortest time ≧ estimated re-encoding time Thus, it is possible to obtain a guarantee that the actual re-encoding process is completed before the code amount exceeds the set value.
[0168]
The encoded data obtained by encoding the encoded data after the re-encoding process at a certain time and the input data are controlled to have the same encoding setting condition so that the image quality is uniform. The condition can also be referred to as a re-encoding setting condition.
[0169]
If the relationship of “(estimated) shortest time ≧ (estimated) re-encoding time” is established (S2609), the process proceeds to step S307 (discard of encoded data in the first memory) in FIG. Returning, in the subsequent quantization step change processing S309, the setting candidate is set as a quantization step.
[0170]
The basic concept of the control flow in the present embodiment will be described using the above-described processing flow. The above-described processing flow in FIG. 26 is integrated with the processing flow in FIG. In other words, the control is performed so that the re-encoding process is always completed before the total code amount W exceeds the set code amount T (W> T) while effectively using the storage memory as in the first embodiment. The method is realized. The integrated processing flow is shown in FIG. The processing flow of FIG. 27 will be described below with a specific example.
[0171]
Assume that the quantization step setting level at the start of encoding is Q1 (JPEG), the image area information conversion setting level is M1 (Packbits), and the compression rate increases as the number representing the setting level increases.
[0172]
The general processing flow is similar to that in FIG. 24, and similarly to FIG. 24, shows processing subsequent to the encoding processing in step S303 (FIG. 12). First, in step S2401, a total sum W of two types of codes (irreversible and lossless codes (the output of the first counter 107 and the output of the fourth counter 1707 in FIG. 25)) is calculated, and the total W is the set code amount T In step S2403, it is detected whether or not the threshold is exceeded. When the total sum W exceeds the set code amount T, it is necessary to re-encode at least one of the codes. Therefore, to determine which code is to be re-encoded, the ratio R of the lossy code amount to the total code amount is calculated in step S2405, and the ratio R is compared with the set code ratio P in step S2407. To do.
[0173]
In order to simplify the explanation, it is assumed that the ratio R is larger than the set code ratio P in the first comparison result. This means that the irreversible code amount (JPEG) is larger than the reference, so that the process proceeds to step S2701 and the quantization step setting candidate is set to Q2. In step S2603, the lossy code amount when re-encoding processing is performed with the setting of Q2 is predicted and calculated, and in step S2605, the shortest time to overflow is estimated. In step S2607, the re-encoding process time is estimated, and in step S2609, it is determined whether the re-encoding process is in time. If the re-encoding process is not in time, that is, the relationship of re-encoding time> shortest time is reached, it is necessary to re-encode the re-encoding process at a higher compression rate. Based on the predicted code amount in the case of conversion, a new lossy code amount ratio R is calculated.
[0174]
If the ratio R is larger than the set code amount ratio P, the quantization step setting candidate is further advanced by one step and set to Q3 (S2701). With the setting of Q3, the lossy code amount is predicted (S2603), the shortest time to overflow is estimated (S2605), and the re-encoding processing time is estimated (S2607). Whether or not is determined (S2609).
[0175]
Here, if a determination result that it is not in time again is obtained, the process returns to step S2405, the ratio R of the lossy code amount corresponding to the quantization step Q3 is calculated (S2405), and compared with the set code amount ratio P (S2407). . Now, it is assumed that the ratio R of the lossy code amount is smaller than the set ratio P. Here, the process proceeds to step S2703 for the first time, and the image area information conversion setting candidate is updated from M1 to M2.
[0176]
For this new setting candidate, this time, reversible code amount (Packbits) prediction (S2603), shortest time to overflow (S2605), re-encoding processing time estimation (S2607) are performed, and re-encoding is performed. It is determined whether the process is in time (S2609). If it is determined that the re-encoding process is in time, the setting candidates Q3 and M2 become the final new compression setting condition, and the process is taken over to step S1201 in FIG.
[0177]
As described above, by effectively increasing the compression setting conditions of the lossy code or lossless code until the re-encoding processing time does not exceed the shortest time until overflow, effective use of the storage memory is achieved. On the other hand, it is possible to realize a control method in which the re-encoding process is always finished before the total code amount W exceeds the set code amount T (W> T).
[0178]
<Third Embodiment>
In the second embodiment, the compression setting conditions for the irreversible code or the lossless code are increased step by step, so that the description is easy to understand. However, there may be a compression setting condition that causes excessive compression even in the second embodiment. Specifically, in the above description, Q3 and M2 are the final compression setting conditions, but the re-encoding processing time does not exceed the shortest time until overflow even in the settings Q2 and M2 where image quality degradation is less than that. It is also possible. That is, there is room for improvement in that this setting can be skipped. The third embodiment improves this.
[0179]
The third embodiment searches all combinations of compression setting candidates of two types of codes, except when it can be clearly excluded. That is, when the code for which the compression setting condition is to be updated changes, it is determined whether or not the re-encoding processing time does not exceed the shortest time until overflow for an unconfirmed compression setting candidate.
[0180]
Specifically, in the description of the second embodiment, when the compression setting candidate of the lossless code is updated from M1 to M2, the irreversible compression condition Q3 at that time is returned to Q1, (Q1, M2), It is determined whether or not the re-encoding processing time is enough in the order of (Q2, M2), (Q3, M2).
[0181]
After that, when the compression setting candidate of the lossless code is updated from M2 to M3, similarly, Q3 is returned to Q1 and re-ordered in the order of (Q1, M3), (Q2, M3), (Q3, M3). It is determined whether the encoding processing time is in time. Further, when updating the lossless code compression setting candidate from M3 to M4, Q3 is returned to Q1, and the re-encoding processing time is changed in the order of (Q1, M4), (Q2, M4), (Q3, M4). Determine if is in time. Thereafter, when the compression setting candidate for the lossy code is updated from Q3 to Q4, M4 is returned to M1, and (Q4, M1), (Q4, M2), (Q4, M3)), (Q4, M4) In this order, it is determined whether the re-encoding processing time is enough.
[0182]
Although the processing slightly increases, this processing is necessary in order not to compress more than necessary in order to suppress image quality deterioration. The following variations are also conceivable as methods for preventing the processing from increasing too much.
[0183]
In the above description, when the reversible compression condition Mn is determined, Qn is returned to Q1, but if Qn is changed back to Q ((n + 1) / 2), specifically, Q3 is returned to Q2. Because the return amount is halved, the processing amount is also reduced by half. It is also possible to consider a method in which an effective return amount when n is small is reflected in a return amount when n is large. As described above, the search range for the two types of compression setting candidates can be variously adjusted.
[0184]
Among the above compression settings, for example, (Q4, M2) remains as a candidate, the encoding process and the re-encoding process are performed on this setting, the code before the re-encoding disappears, and the code of the setting is generated Suppose that If the sum W of the two types of code amount does not overflow even if the image is encoded to the end with this setting (if the set code amount T is not exceeded), this setting becomes the final compression setting condition for the image. . If W causes an overflow, it is detected in step S2407 in FIG. 27, and a new compression setting candidate is searched. When the compression setting condition of the code to be re-encoded is (Q4, M2), it is meaningless to search for Q1, Q2, Q3, M1, which are settings with a lower compression rate than that. This is because information lost by processing cannot be returned. Therefore, the process of “returning Qn to Q1” in the above description is replaced with the process of “returning Qn to Q4”. In other words, it can be said that the compression setting condition of the code to be re-encoded is restored.
[0185]
FIG. 28A shows the search range in the initial state (Q1, M1) and the search example described above, and FIG. 28B shows the next search range and search example in which the compression setting candidate is fixed at (Q2, M4). Shown in
[0186]
In each of the above-described embodiments, the functional operation of the apparatus has been described using the apparatus that reads an image from the image scanner as an example. Most of the functions (including the encoding process) can be realized by a computer program as described above.
[0187]
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 as a compression source 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.
[0188]
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. Further, since the computer program is normally performed by setting or copying or installing a storage medium such as a floppy (registered trademark) disk or CDROM in the apparatus, such a storage medium is naturally included in the scope of the present invention.
[0189]
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.
[0190]
The present invention can also be applied to a combination of a computer program and appropriate hardware (such as an encoding circuit).
[0191]
As described above, according to the present embodiment, lossy encoding means for irreversibly compressing image data, and means for re-encoding encoded data obtained by the encoding means so as to increase the compression rate; ,
Lossless encoding means for reversibly compressing image area information, and encoded data obtained by reversibly compressing reversible encoded data obtained from the lossless encoding means by rewriting the image area information so that the entropy of the image area information is reduced. Reversible code re-encoding means for converting to
A storage unit having a predetermined capacity capable of storing the two types of encoded data;
Coded data to be re-encoded next and compression setting based on the data amount of each code, estimated code amount after re-encoding, estimated shortest time until overflow of total code amount, re-encoding processing time, etc. By searching for the conditions, it has become possible to perform compression such that the image data and the two types of codes obtained by encoding the image area information are combined and fall within the code amount within the target value.
[0192]
The embodiments according to the present invention have been described above. However, the spirit and scope of the present invention are not limited to the specific descriptions and drawings of the present specification, and are all described in the claims of the present application. It will be understood that this will cover various modifications and changes.
[0193]
Based on FIG. 25, the embodiment of the present invention will be as follows.
[0194]
[Embodiment 1] An image processing method for compressing and encoding image data and image area information of the image data,
A first irreversible compression step for image data, the compression parameters of which can be changed;
A second irreversible compression step for image data, the compression parameter of which can be changed, the code compressed in the first irreversible compression step is decoded and the lossy compression is performed again;
A first lossless compression step for image area information, the compression parameters of which can be changed;
The compression parameter can be changed, the code compressed in the first lossless compression step is decoded, and a specific image area value of the image area information obtained by decoding is changed to another image area value according to the compression parameter. A second lossless compression step for image area information to convert and perform lossless compression;
It is determined whether or not the total code amount of the code amount generated by each of the first lossy compression step and the first lossless compression step has reached a predetermined amount. A code amount monitoring step to perform,
When it is determined by the encoding amount monitoring step that the total code amount has reached the predetermined amount, the correlation between the code amount by the first lossy compression step and the code amount by the first lossless compression step A determination step for determining information on which compression parameters are to be changed based on the relationship;
When it is determined by the determining step that the object whose compression parameter is to be changed is image data, it is determined that the compression parameters of the first and second lossy compression steps are updated and the predetermined amount is reached. The image data input later is compressed in the first lossy compression step, and the previously compression-coded image data determined to have reached the predetermined amount is compressed in the second lossy compression step. Let it perform lossy compression,
When it is determined by the determining step that the object whose compression parameter is to be changed is image area information, it is determined that the compression parameter of the first and second lossless compression steps has been updated and the predetermined amount has been reached. Image area information to be input later is compressed in the first lossless compression process, and previously compressed and encoded image area information determined to have reached the predetermined amount is compressed in the second lossless compression process. A control process for performing reversible compression;
An image processing method comprising:
[0195]
[Embodiment 2] In the determination step, the ratio of the code amount of image data and the code amount of image area information set in advance, the code amount in the first lossy compression encoding step, and the first lossless code amount are determined. The image processing method according to the first embodiment, wherein a target for updating a compression parameter is determined based on a code amount ratio in the compression encoding step.
[0196]
[Embodiment 3] The determination step includes:
The ratio of the code amount of image data and the image amount of image area information set in advance, and the ratio of the code amount in the first lossy compression encoding step and the code amount in the first lossless compression encoding step. A first step of temporarily determining the compression parameter update target and the compression parameter,
A second step of calculating a recompression prediction time required when recompression is performed with the compression parameter update target and the compression parameter temporarily determined and a predicted arrival time for reaching the set amount again in the first step; And the process of
By the second step,
Recompression predicted time <predicted arrival time
If the above condition is satisfied, a third step in which the provisionally determined compression parameter change target and the compression parameter are finally determined,
When the condition is not satisfied, the estimated code amount of the image data and the estimated code amount of the image area information when it is assumed that compression encoding is performed in the provisional determination, the code amount of the image data in the first step, and A fourth step of repeating the first to third steps as a code amount of the image area information;
The image processing method of Embodiment 1 characterized by including.
[0197]
[Embodiment 4] In the first step, when the compression parameter update target and the compression parameter are determined, the compression parameter of the information that is the other target is provisionally determined with a compression parameter that provides a low compression rate. The image processing method of Embodiment 3 characterized by these.
[0198]
In addition, although the above is an aspect about a method, when it is set as an apparatus invention, what is necessary is just to express as a means which implement | achieves the function corresponded to each said process, and the structure which functions as each means when implement | achieving by a computer program It would be good if Further, it may be clear that the computer readable storage medium stores a computer program.
[0199]
Moreover, if FIG. 23 is used as the basis, it will be as follows.
[0200]
[Embodiment 5] An image processing method for compressing and encoding image data and image area information of the image data,
A first lossy compression encoding process for image data in which compression parameters can be changed;
A second irreversible compression encoding process for image data, the compression parameter of which can be changed, and compression-encoded with a compression parameter having a higher compression ratio than the first irreversible compression encoding process;
Decoding the code data compressed in the second lossy compression encoding step, and a third lossy compression encoding step for image data to be re-encoded;
A first lossless compression encoding process for image area information with variable compression parameters;
A second lossless compression encoding step for image area information, the compression parameters of which can be changed, and compression encoded with a compression parameter having a higher compression ratio than the first lossless compression encoding step;
A third lossless compression encoding step for image area information for decoding and re-encoding the code data compressed in the second lossless compression encoding step;
Whether or not the total code amount of the code amount generated by each of the first lossy compression encoding step and the first lossless compression step during compression encoding has reached a predetermined amount A code amount monitoring step for determining
When it is determined by the encoding amount monitoring step that the total code amount has reached the predetermined amount, the correlation between the code amount by the first lossy compression step and the code amount by the first lossless compression step A determination step for determining information on which compression parameters are to be changed based on the relationship;
A control step for controlling the first to third lossy compression steps and the first to third lossless compression steps with the contents determined in the determination step;
The control process is
When it is determined that the object whose compression parameter is changed by the determination step is image data,
Updating the compression parameters of the first and second lossy compression encoding processes;
For the first lossy compression encoding step, the second lossy compression encoding step is inherited and the compression process is continued.
For the third lossy compression encoding step, re-encode the image data compressed and encoded in the second lossy compression encoding step before it is determined that the predetermined amount has been reached,
When the determination step determines that the object whose compression parameter is to be changed is image area information,
Updating the compression parameters of the first and second lossless compression encoding steps;
For the first lossless compression encoding process, the compression process is continued by inheriting the second lossless compression encoding process,
For the third lossless compression encoding step, the image area information compression encoded in the second lossless compression encoding step before it is determined that the predetermined amount has been reached is re-encoded.
An image processing method.
[0201]
It should be noted that, in the fifth embodiment, the second to fourth embodiments described above can be incorporated as preferable examples, and can also be realized as an apparatus, a computer program, and a computer-readable storage medium. Of course.
[0202]
【The invention's effect】
As described above, according to the present invention, during compression encoding while inputting image data and image area information, even when the total code amount reaches a set amount, While continuing to input image data and image area information, it is possible to control the code amount to be close to the set amount while minimizing image quality degradation.
[Brief description of the drawings]
FIG. 1 is a block diagram of an image processing apparatus according to a first example which is a premise of the present invention.
FIG. 2 is a block configuration diagram of an image processing apparatus in a second example.
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 diagram of an image processing apparatus according to a third example.
FIG. 18 is a flowchart illustrating a processing procedure in the third example.
FIG. 19 is a diagram illustrating processing contents of Packbits encoding.
FIG. 20 is a diagram illustrating processing contents of Packbits encoding in the third example.
FIG. 21 is a block diagram of an image processing apparatus according to a fourth example.
FIG. 22 is a flowchart illustrating a processing procedure in the fourth example.
FIG. 23 is a block diagram of an image processing apparatus according to the first embodiment.
FIG. 24 is a flowchart of a main part of a processing procedure in the first embodiment.
FIG. 25 is a block diagram of an image processing apparatus according to the second embodiment.
FIG. 26 is a flowchart of a main part of a processing procedure in the second embodiment.
FIG. 27 is a flowchart of a main part of a processing procedure in the second embodiment.
FIG. 28 is a diagram illustrating a transition of an encoding parameter in the third embodiment.

Claims (5)

An image processing apparatus that compresses and encodes image data and image area attribute data represented by a plurality of bits for each pixel of the image data,
First image encoding means for compressing and encoding the input image data in accordance with an image compression parameter;
Second image encoding means for decoding encoded data generated by the first image encoding means and recompressing and encoding according to the compression parameters for the image;
First attribute encoding means for compressing and encoding the input image area attribute data in accordance with an image area compression parameter;
Decoding the encoded data generated by the first attribute encoding means, the image area attribute of the bit specified by the compression parameter for the image area in the image area attribute data obtained by decoding, other Second attribute encoding means for converting to a value indicating the image area attribute and performing recompression encoding;
During the compression encoding by the first image encoding unit and the first attribute encoding unit, the total code amount of the encoded data generated by each reaches a set amount. Monitoring means for determining whether or not,
When the monitoring unit determines that the total code amount has reached the set amount, the data amount of the encoded data generated by the first image encoding unit and the first attribute encoding unit Based on the correlation of the data amount of the encoded data generated in step 1, the first and second image encoding means or the first and second attribute encoding means are used as compression parameter update targets. A determination means for determining whether to
When the determination unit determines that the compression parameter update target is the first and second image encoding units, the compression parameter for the image of the first and second image encoding units is updated and the setting is performed. The image data input after it is determined that the amount has been reached is compressed and encoded by the first image encoding means in accordance with the compression parameters for the updated image, and before it is determined that the set amount has been reached For the encoded data generated by the first image encoding means, the second image encoding means performs recompression encoding according to the updated image compression parameters,
When the determination unit determines the compression parameter change target to be the first and second attribute encoding units, updates the compression parameters for the image areas of the first and second attribute encoding units, The image area attribute data input after it is determined that the set amount has been reached is compression-encoded by the first attribute encoding means according to the updated image area compression parameters, and the set amount has been reached. Control for causing the second attribute encoding unit to perform recompression encoding on the encoded data generated by the first attribute encoding unit before the determination in accordance with the compression parameter for the updated image area and means,
The determining means includes
The ratio between the encoded data amount of the image data set in advance and the encoded data amount of the image area attribute data, the data amount of the encoded data generated by the first image encoding means, and the first attribute code First means for tentatively determining a compression parameter update target and a compression parameter based on a ratio of the amount of code data generated by the conversion means;
A second means for calculating a recompression prediction time required when recompressing with the compression parameter update target and the compression parameter temporarily determined and a predicted arrival time for reaching the set amount again by the first means; Means of
Recompression prediction time and prediction arrival time obtained by the second means
Recompression predicted time <predicted arrival time
If the above condition is satisfied, third means for final determination of the compression parameter change target and the compression parameter that are provisionally determined;
When the condition is not satisfied, the estimated code amount of the image data and the estimated code amount of the image area attribute data when it is assumed that compression encoding is performed by the provisional determination are performed. the image processing apparatus characterized by comprising a fourth means for data amount of the data and the data amount of the encoded data of the image area attribute data to repeat the first to third means. It said first means, when the subject of updating the compression parameters were determined compression parameter, the compression parameter of the other object to claim 1, characterized in that provisionally determines the compression parameters that are low compression ratio The image processing apparatus described. A control method of an image processing apparatus that compresses and encodes image data and image area attribute data represented by a plurality of bits for each pixel of the image data,
A first image encoding step in which the first image encoding means compresses and encodes the input image data in accordance with an image compression parameter;
A second image encoding step, wherein the second image encoding means decodes the encoded data generated in the first image encoding step, and recompresses and encodes according to the compression parameter for the image;
A first attribute encoding step, wherein the first attribute encoding means compresses and encodes the input image area attribute data in accordance with an image area compression parameter;
The second attribute encoding means decodes the encoded data generated in the first attribute encoding step, and is specified by the compression parameter for the image area in the image area attribute data obtained by decoding. A second attribute encoding step of converting the image area attribute of a bit to a value indicating another image area attribute and performing recompression encoding;
The total code amount of the data amount of the encoded data generated by each of the monitoring means is set during the compression encoding in the first image encoding step and the first attribute encoding step. A monitoring process to determine whether the quantity has been reached,
When it is determined by the monitoring step that the total code amount has reached the set amount, the amount of encoded data generated in the first image encoding step and the first attribute encoding step Based on the correlation of the data amount of the encoded data generated in step 1, the first and second image encoding steps or the first and second attribute encoding steps are used as compression parameter update targets. A determining step in which the determining means determines whether or not
The control means
When it is determined in the determination step that compression parameter update targets are the first and second image encoding steps, the compression parameters for images in the first and second image encoding steps are updated, and the setting is performed. The image data input after it is determined that the amount has been reached is compression-encoded in the first image encoding step according to the compression parameter for the image after the update, and before it is determined that the set amount has been reached In addition, the encoded data generated in the first image encoding step is subjected to recompression encoding in the second image encoding step according to the compression parameter for the image after the update,
When determining the compression parameter change target as the first and second attribute encoding steps by the determining step, update the compression parameters for the image areas of the first and second attribute encoding steps, The image area attribute data input after it is determined that the set amount has been reached is compression-encoded in the first attribute encoding step according to the updated image area compression parameters, and the set amount is reached. Control for causing the second attribute encoding step to perform recompression encoding on the encoded data generated in the first attribute encoding step before the determination in accordance with the compression parameter for the updated image area A process,
The determination step includes
The first means is a ratio of the encoded data amount of the image data and the encoded data amount of the image area attribute data set in advance, and the data amount of the encoded data generated by the first image encoding means, A first step of tentatively determining a compression parameter update target and a compression parameter based on a ratio of the amount of code data generated by the first attribute encoding means;
The second means is the compression parameter update target temporarily determined in the first step and the recompression prediction time required for recompression with the compression parameter; and the predicted arrival time for reaching the set amount again. A second step of calculating
The third means is that the recompression prediction time and the prediction arrival time obtained in the second step are:
Recompression predicted time <predicted arrival time
If the above condition is satisfied, a third step in which the provisionally determined compression parameter change target and the compression parameter are finally determined;
When the fourth means performs the first step, the estimated code amount of the image data and the estimated code amount of the image area attribute data when it is assumed that compression encoding is performed by the provisional determination when the condition is not satisfied. And a fourth step of repeating the first to third steps as the amount of encoded data of the image data and the amount of encoded data of the image area attribute data. Control method. By computer executes seen read, causes the computer to function as the image processing apparatus according to the computer to claim 1 or 2. A computer-readable storage medium storing the computer program according to claim 4 .

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