JP3753580B2 - Data encoding method, data decoding method, and computer-readable recording medium recording a program for causing a computer to execute the method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention sequentially inputs a run-length numerical sequence obtained by scanning data as a unit of a set of 0 bit continuations and 1 bit continuations as an input unit, converts the data into a predetermined code sequence, and outputs the data code Method, data code obtained by scanning a code string data and inputting a code string obtained by scanning the code string data, and restoring and outputting a run-length numeric string in units of a set of 0 bit continuation number X and 1 bit continuation number Y And a computer-readable recording medium on which a program for causing a computer to execute the method is recorded.
[0002]
[Prior art]
Conventionally, a printing apparatus such as a laser printer compresses (encodes) image data to be printed, temporarily stores it in a memory, and performs actual printing while decompressing (decoding) the compressed data stored in the memory. A memory-saving technique is known that reduces the memory capacity of a memory for storing image data.
[0003]
The original purpose of such a memory-saving technique is to reduce the memory capacity of the memory for storing the image data to reduce the cost. Therefore, it is necessary to provide complicated dedicated hardware for compressing or expanding the image data. It is not appropriate, and it is necessary to cause the microprocessor of the printing apparatus to perform these processes in software.
[0004]
Here, as a two-dimensional still image encoding technique, two-dimensional compression techniques that perform data compression in consideration of data correlation in the sub-scanning direction and predictive encoding techniques that perform predictive encoding using arithmetic codes are highly compressed. It is known as a technology that can obtain rates.
[0005]
However, if these encoding technologies are implemented by software using a microprocessor of a printing apparatus, processing delays occur, and in recent years, the printing resolution and printing speed are improved day by day. It is not efficient to use. For this reason, a relatively simple compression technique called one-dimensional compression is widely used when the microprocessor performs compression / decompression.
[0006]
As a conventional one-dimensional compression technique, an MH (Modified Haffman) code used in a run-length process or a facsimile machine is widely known, but a color (black and white) such as a pseudo halftone image has a short cycle. In the case of image data that changes frequently, it cannot be compressed efficiently. In particular, since the opportunity to print image data has increased with the progress of personal computers and networks, it is not efficient to employ this MH code as a memory saving mechanism.
[0007]
For this reason, in order to improve the compression rate of image data whose color frequently changes in a short cycle, an encoding technique for detecting repeatability of image data and run length is known. For example, in Japanese Patent No. 2683506 (Prior Art 1), by using a control word that can describe both the length of a white word and the length of a black word, the white word and the black word are controlled in a relatively short cycle. A data compression (decompression) method and apparatus for efficiently compressing image data that appears automatically is disclosed.
[0008]
Specifically, in this prior art 1, a certain word length (byte) is defined, a data unit that is all white is treated as a white word, a non-white data unit is treated as a black word, the number of repeated occurrences thereof, Since the contents of black words, control words, etc. are encoded in units of word lengths, no special code table is required for encoding and decoding, and processing can be performed in units of word lengths so that even microprocessors can process them. Sufficient processing performance can be expected.
[0009]
Japanese Laid-Open Patent Publication No. 9-65147 (prior art 2) stores white and black run lengths, and a predetermined value is obtained when the run length value of a certain color matches the run length value immediately before the same color. An image signal compression (decompression) method and apparatus for improving the compression rate and processing speed by generating a repetitive code is disclosed.
[0010]
[Problems to be solved by the invention]
However, in the above prior art 1, since repeatability is detected in units of word strings, a high compression rate is obtained only when the repetition period included in the target image data and the word length match or become a multiple. There is a problem that sufficient compression cannot be obtained for general image data.
[0011]
Further, in the above-described prior art 2, the compression rate is only when the amount of data is sufficiently smaller than the codeword encoded when the repetitive codes generated when the run lengths match do not match. There is a problem that this is only an improvement. That is, assigning shorter codewords to repetitive codes lengthens codewords with relatively unmatched run lengths, so a sufficient compression ratio for image data whose colors change frequently in short cycles It is difficult to obtain a code set having.
[0012]
Specifically, in the embodiment of the prior art 2, the code set is similar to the MH code, and high speed as in the run-length code technique cannot be expected in the processing by the microprocessor. In addition, since a storage unit for storing run-length values is provided corresponding to colors, it is necessary to select a reference / storage destination according to colors when comparing and storing run-length values. There is also a problem that high-speed processing by the processor is hindered.
[0013]
The two-dimensional compression technique, the predictive coding technique, the MH coding, and the like have a problem that a relatively large capacity memory such as a line buffer, a probability table, and a code table is required. For example, if the resolution is 1200 dpi (dots / inch) and the printing speed is 25 ppm (pages / minute), the pixel frequency generally exceeds 100 MHz. It is extremely difficult to operate the encoding / decoding hardware circuit including the memory at such a frequency, and even if the circuit is operated in parallel and operated at a low frequency, it is parallel including the table. As a result, it becomes a large-scale circuit, resulting in an increase in cost.
[0014]
Further, Japanese Patent Application No. 11-12479 is configured to reduce the number of codes by encoding the number of consecutive runs when the run length value matches the run length value immediately preceding the same color. Data encoding and decoding methods that can achieve both a high compression rate and high processing speed for pseudo-halftone image data are described. In the case of image data including an image, a sufficient compression rate cannot be obtained.
[0015]
In order to eliminate the above-mentioned problems caused by the prior art, the present invention can efficiently compress pseudo halftone image data generated by error diffusion processing, and data encoding suitable for software processing by a microprocessor. It is an object of the present invention to provide a method, a data decoding method, and a computer-readable recording medium recording a program for causing a computer to execute the method.
[0016]
[Means for Solving the Problems]
  In order to solve the above-described problems and achieve the object, a data encoding method according to the first aspect of the present invention provides a run length obtained by scanning data.ValueA data encoding method in which a sequence is sequentially input as an input unit of a set of 0 consecutive bits and 1 consecutive bits, converted into a predetermined code sequence, and output.As the calculation of the state value corresponding to the data of the input unit, the number of consecutive 0 bits X, the number of consecutive 1 bits Y, the number of consecutive 0 bits A immediately before, and the number of consecutive 1 bits immediately preceding 1 When B is in the relationship of X ≠ A and Y ≠ B, the value of the state S0 is the state value S, and when X = A and Y ≠ B, the value of the state S1 is the state value S, and X A calculation step of calculating the value of state S2 as state value S when ≠ A and Y = B, and calculating the value of state S3 as state value S when X = A and Y = B; When the immediately preceding state value T is the state S3 and the state value S and the immediately preceding state value T are the same coincidence event, this is regarded as a repetitive event, and the repetitive event occurs continuously. The iteration number calculating step for calculating the iteration number N, and the state value S and the immediately preceding state after the occurrence of the iteration event. A non-coincidence event different from the value T or a regression event determination step for determining a regression event when the input is completed, and a state code generation for generating a state code indicating the value of the state value S when the mismatch event occurs And a numerical code indicating the value of the consecutive number X of 0 bits or the consecutive number Y of 1 bits when the generation of the state code by the state code generating step is completed or the coincidence event occurs A first numerical code generation step for generating the number of iterations N and the number N of iterations calculated by the iteration number calculation step prior to the generation of the state code by the state code generation step when the regression event occurs A second numerical code generation step for generating a numerical code, and a generation step for generating a state code and a numerical code corresponding to the input unit data,It is characterized by including.
[0017]
  According to the invention of claim 1,In the calculation of the state value corresponding to the data of the input unit, the number of consecutive 0 bits X, the number of consecutive 1 bits Y, the number of consecutive 0 bits A immediately before, and the number of consecutive 1 bits B immediately preceding When X ≠ A and Y ≠ B, the value of the state S0 is the state value S. When X = A and Y ≠ B, the value of the state S1 is the state value S, and X ≠ A and The value of the state S2 is set as the state value S when Y = B, and the value of the state S3 is calculated as the state value S when X = A and Y = B. Is the state S3, and the state value S and the previous state value T are equal coincident events, this is regarded as a repetitive event, and the repetitive number N in which the repetitive event occurs continuously is calculated. When a repetitive event occurs, the status value S and the previous status value T are different from each other, or the input is completed. When a mismatch event occurs, a status code indicating the value of the status value S is generated. When the generation of the status code ends or a match event occurs, the number of consecutive 0 bits X Alternatively, a numerical code indicating the value of the consecutive number Y of 1 bits is generated, and when a regression event occurs, the numerical code indicating the value of the iteration number N is generated prior to the generation of the state code. Using the concept of event, mismatch event, repetitive event, and regression event, it is possible to efficiently compress the pseudo halftone image data generated by the error diffusion process.
[0022]
  Claims2The data encoding method according to the present invention is as follows.1In the invention, the calculation step includes an initialization step of storing predetermined initial values in T, A, B, and the number of iterations N, respectively, when encoding is started;SaidAn input step for inputting a run-length value; and a state value generating step for generating the state value S after input by the input step, wherein the generating step uses the state value S generated by the state value generating step. Corresponding event determination step for determining occurrence of the coincidence event or mismatch event, repetitive event determination step for determining whether or not the repetitive event has occurred in response to occurrence of the coincidence event, and occurrence of the repetitive event An iteration number adding step of adding the iteration number in response to the occurrence of the mismatch event or a regression event determining step of determining whether or not the regression event has occurred in response to the end of the encoding target data, and the regression An iterative number numerical code generation step for generating an iterative number numerical code indicating the value of the iterative number N in response to the occurrence of an event, and a regression for returning the iterative number N to a predetermined initial value after generating the iterative number numerical code A state code generation step for generating a state code representing the value of the state value S in response to occurrence of the mismatch event or initialization of the number of iterations N by the regression step, and a state by the state code generation step After generation of a code or determination of occurrence of a repetitive event by the repetitive event determination step, if X does not match A, a numerical code corresponding to X is generated, and if Y does not match B, Y is set to Y After the numerical code generation step for generating the corresponding numerical code, and the generation of the numerical code by the numerical code generation step or the addition of the number of iterations N by the number of iterations addition step, the content of A is updated to X, And updating the contents to Y and updating the contents of T to S immediately before updating.
[0023]
  This claim2According to the invention, when encoding is started, predetermined initial values are stored in T, A, B and the number of repetitions N, respectively, and X and YTo laThe length value is input, and after this input, the state value S is generated, the occurrence of the coincidence event or the disagreement event is determined corresponding to the generated state value S, and the occurrence of the repetitive event is generated in response to the occurrence of the coincidence event Determine the presence or absence, add the number of iterations in response to the occurrence of a repetitive event, determine the presence or absence of a regression event in response to the occurrence of a discrepancy event or the end of data to be encoded, and In response, an iteration number numerical code indicating the value of the iteration number N is generated. After the iteration number numeric code is generated, the iteration number N is returned to a predetermined initial value, and in response to the occurrence of a mismatch event or the initialization of the iteration number N. A state code expressing the value of the state value S is generated, and after generation of the state code or determination of occurrence of a repetitive event, if X does not match A, a numerical code corresponding to X is generated, and Y is B If it does not match, generate a numeric code corresponding to Y After generating the numerical code or adding the number of iterations N, the contents of A are updated to X, the contents of B are updated to Y, and the contents of T are updated to S. You can compress the data that fits.
[0024]
  Claims3The data decoding method according to the present invention inputs a code string obtained by scanning the code string data, and has a run length in units of a set of 0 bit continuation number X and 1 bit continuation number Y.ValueA data decoding method for restoring and outputting to a column, wherein when decoding is started, a storage unit S that stores a state value to be restored, and a value corresponding to X among the restored run length values An initialization step of initializing a storage unit C to be stored and a storage unit D to store a value corresponding to the Y of the restored run length values by substituting a predetermined initial value, and a predetermined code unit are input. An input code type determining step for determining whether the code is a numerical code P or a state code Q, and when the input code type determining step determines that the code is a numerical code, the code is restored to a numerical value. A numerical code restoration step stored in the storage unit L, and a state code restoration step for restoring the code to the state value and storing it in the S when the input code type determination step determines the state code; State at the time when the restoration value is stored in L State S0 where X ≠ A and Y ≠ B, S1 where X = A and Y ≠ B, S2 where X ≠ A and Y = B, or X = A And an identification step for identifying which state S3 is in a relationship of Y = B (where A is the number of consecutive 0 bits immediately before and B is the number of consecutive 1 bits immediately preceding); When a new state value is stored in S, the S3 state determination step for determining whether or not the value of S matches S3, and the value of S is S0 by the identification step In the case of being identified, after the value of L is stored in the C, the next numerical code is input and restored, and the first run value updating step of storing in the D is performed. A second run value that stores the value of L in D when the value is identified as S1 A new run value, a third run value updating step of storing the value of L in the C when the value of S is identified as the S2 by the identification step, the first, second or When updating by the third run value updating step is completed or when it is determined by the S3 state determination step that the value of S matches the state value S3, the C and D values are set to a set of run length values. And when the S value is identified as S3 by the identification step, the C and D values are set to the L value as a set of run length values. And a second output step for outputting the corresponding number of times.
[0025]
  This claim3According to the invention, when starting decoding, the storage unit S that stores the restored state value, the storage unit C that stores the value corresponding to the X among the restored run-length values, and the restored A predetermined initial value is substituted into a storage unit D for storing a value corresponding to Y among the run length values, and a predetermined code unit is input, so that the code is a numerical code P or a state code Q If it is determined to be a numerical code, the code is restored to a numerical value and stored in the storage unit L. If it is determined to be a state code, the code is restored to a state value to S The state value S at the time when the restored numerical value is stored and stored in L is the state S0 where X ≠ A and Y ≠ B, and the states S1 and X where X = A and Y ≠ B Neither state S2 in the relationship of ≠ A and Y = B or state S3 in the relationship of X = A and Y = B When a new state value is stored in S, it is determined whether or not the value of S matches S3, and when the value of S is identified as S0, After the value of L is stored in C, the next numerical code is input and restored and stored in D. When the value of S is identified as S1, the value of L is stored in D and the value of S Is determined to be S2, the value of L is stored in C, and when updating is completed or when it is determined that the value of S matches the state value S3, a set of values of C and D is set. When the S value is identified as S3, the C and D values are output as a set of run length values for the number of times corresponding to the L value. It is possible to efficiently restore the compressed halftone image data generated by the error diffusion process.
[0026]
  Claims4The recording medium according to the present invention is the first aspect.3By recording a program that causes a computer to execute the method described in any one of the above, the program can be machine-readable, and thereby3Any one of the operations can be realized by a computer.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Exemplary embodiments of a data encoding method, a data decoding method, and a computer-readable recording medium storing a program for causing a computer to execute the method according to the present invention are described in detail below with reference to the accompanying drawings. explain. In the present embodiment, the case where the pseudo halftone image data generated by the error diffusion process is encoded or decoded is shown.
[0028]
First, the concept of the data encoding method and the data decoding method according to the present embodiment will be described. FIG. 1 is an explanatory diagram for explaining the concept of the data encoding method and the data decoding method according to the present embodiment.
[0029]
In the figure, for a run-length numerical sequence obtained by scanning data, the number of consecutive bits having a value of “0” (hereinafter referred to as “X”) and the number of consecutive bits having a value of “1”. Data encoding is performed in which a set (hereinafter referred to as “Y”) is sequentially input as an input unit, converted into a predetermined code string, and output.
[0030]
Specifically, the value immediately before X is “A”, the value immediately before Y is “B”,
X ≠ A and Y ≠ B
Let S0 be the state of
X = A and Y ≠ B
Let S1 be the state of
X ≠ A and Y = B
Let S2 be the state of
X = A and Y = B
Let S3 be the state.
[0031]
Further, a state value having any value of S0 to S3 according to this state is “S”, and a value immediately before this S is “T”. Then, an event where S = T is set as a “general event”, an event where S ≠ T is set as a “mismatch event”, and if a match event occurs when T is S3, it is set as a “repeated event”. The number of consecutive occurrences of events is defined as “repetition number N”.
[0032]
Furthermore, after this repetitive event occurs, if a mismatch event occurs or input is completed, it is set as a “regression event”. If a mismatch event occurs, a state code Q indicating the value of the state value S is generated, When the code generation is completed or when a coincidence event occurs, a numerical code P indicating the value of X is generated when X ≠ A, and a numerical code indicating the value of Y when Y ≠ B P is generated, and when a regression event occurs, a numerical code P indicating the value of the iteration number N is generated prior to the generation of the state code.
[0033]
FIG. 1 shows a case where the data to be compressed starts with “0” of 3 bits and continues to “1” of 4 bits and “0” of 3 bits. When the run length measurement is started from “0”, the X and Y numeric sequences obtained by scanning the data have a continuous number of “0” and a continuous number of “1”, respectively. Are sequentially input to the encoding unit.
[0034]
In the figure, each numerical value, event, and generated code for each input value are shown, but for each event, “○” is described when there is an event, and blank when there is no event. It is said. For each code, “◯” is described when there is a code output, and blank when no code is output.
[0035]
Here, although there are two attributes of a status code and a numerical code, the numerical code is divided into three types so that it can be understood which numerical value corresponds. Strictly speaking, the previous values (A, B and T) do not exist in the first X, Y and S of the data, but here the initial values of A, B and S are all “0”. And
[0036]
As described above, in the present embodiment, when events whose run length values match the run length value immediately before the same measurement target value continue, the number of codes is reduced by encoding the continuous number. The number of codes is efficiently reduced by inheriting the feature of the technology by generating a numerical code P corresponding to the number of repetitions N when S3 continues multiple times. In addition, the number of codes is efficiently reduced when either X or Y matches the previous value but the other does not match, that is, when the state of S1 or S2 continues.
[0037]
In particular, in error-diffused image data, the probability that the states of S1 and S2 are continuous is high, so the effect of reducing the number of codes according to this embodiment is great. For example, in the same figure, 12 sets, that is, 24 run length values are input, but it is understood that the number of codes to be output is reduced to 11, and the number of codes is reduced.
[0038]
Next, an encoding procedure used in this embodiment will be described. FIG. 2 is a flowchart showing the encoding procedure used in this embodiment, and FIG. 3 is a flowchart showing the non-output N encoding procedure shown in steps S209 and S219 of FIG.
[0039]
As shown in FIG. 2, first, initialization processing is performed in which predetermined constants C are set in A, B, and T, and N is set to 0 (step S201). Here, for convenience of explanation, the same constant C is set for A, B, and T, but different values may be set. However, it is desirable that the initial value of T is the value shown in S0 in order to reduce the number of codes. The reason is that the generation of the state code due to the occurrence of a meaningless mismatch event can be suppressed because the case where the state value S is S0 occurs with the highest probability for the first input of X and Y. In addition, it is desirable that the initial values of A and B are set to values different from the values at the start of run length measurement in order to reduce the number of codes.
[0040]
When the initialization process is completed, an input process for inputting and storing a set of run length values in X and Y is performed (step S202), and a predetermined state S is generated corresponding to this input. State creation processing is performed (steps S203 to S207).
[0041]
Specifically, after initializing by substituting 0 for the S value (step S203), the X value and the A value are compared (step S204), and if they match (Yes in step S204). “1” is added to this S (step S205), and if they do not match (No at step S204), the process proceeds to step S206 as it is. Further, the Y value is compared with the B value (step S206), and if they match (Yes at step S206), '2' is added to S (step S207). Therefore, the numerical value representing S0 is 0, the numerical value representing S1 is 1, the numerical value representing S2 is 2, and the numerical value representing S3 is 3.
[0042]
Thereafter, a matching event determination process is performed to determine whether or not the value of the generated state value S matches T (step S208). If they match (Yes in step S208), it is determined as a matching event. If they do not match (No at Step S208), it is determined that the event is a mismatch event.
[0043]
Specifically, when a coincidence event occurs (Yes at Step S208), it is determined whether or not the S value is 3 (Step S211), and when this S value coincides with 3, that is, S3 (Step S211). S211 Yes) It is determined that there is a repetitive event, the value of the number of repetitions N is incremented (step S212), and the process proceeds to step S217.
[0044]
On the other hand, if a mismatch event has occurred (No at step S208), it is determined that no repetitive event has occurred, and non-output N encoding is performed (step S209). Specifically, as shown in FIG. 3, it is determined whether or not the value of the iteration number N is greater than 0 (step S301). If it is greater than 0 (step S301 affirmative), a regression event occurs. After determining that it has been performed and performing numerical encoding (N) and outputting a numerical code (step S302), initialization is performed by substituting 0 for N (step S303). On the other hand, when the value of the iteration number N remains 0 (No at step S301), it is determined that no regression event has occurred.
[0045]
When this non-output N encoding is completed, state encoding (S) for generating and outputting a state code representing the value of state S is performed (step S210), and run numerical code output processing is performed (step S210). S213 to S216).
[0046]
Specifically, first, the X value and the A value are compared (step S213), and if they do not match (No in step S213), a numerical code (X that generates and outputs a state code representing the value of X) (X ) Is performed (step S214). Also, the Y value and the B value are compared (step S215), and if they do not match (No at step S215), the state code expressing the Y value is generated and output (Y) (step S215). Step S216).
[0047]
Thereafter, A is updated with the X value, B is updated with the Y value, and T is updated with the S value (Step S217). If there is data to be encoded (No at Step S218), Step The process proceeds to S202 and the above process is repeated. If there is no more data to be encoded (Yes at step S218), the previously described non-output N encoding is performed (step S219), and the process is terminated.
[0048]
By performing the above-described series of processing, when a mismatch event occurs, a state code Q indicating the value of the state value S is generated. When code generation is completed or when a match event occurs, X ≠ A In some cases, a numerical code P indicating the value of X is generated. In a case where Y ≠ B, a numerical code P indicating the value of Y is generated. When a regression event occurs, a state code is generated. A numerical code P indicating the value of the iteration number N can be generated and encoded in advance.
[0049]
When the above processing procedure is realized by software, an appropriate memory may be allocated to X, Y, A, B, S, T, and N, but it is possible to use a general-purpose register of a microprocessor. Desirable for improving performance. The constant C and each control can be realized by describing them as a program, that is, an instruction code.
[0050]
Further, in the above series of explanations, for the convenience of explanation, the run length measurement input (step S202) and related data end determination (step S218) and code generation (steps S210, S214, S216, S302) are described in detail. Omitted.
[0051]
Next, a data decoding procedure according to this embodiment will be described. FIG. 4 is a flowchart showing a data decoding procedure according to the present embodiment. As shown in the figure, when starting the decoding process, S for storing the restored state value, A for storing the value corresponding to X among the restored run length values, and the value corresponding to Y Is initialized by substituting a constant C for each B stored (step S401). In order to perform decoding correctly, the initial values assigned to A, B, and S are the values assigned to A, B, and S during the initialization process during encoding (step S201 in FIG. 2). It is necessary to assign the same value.
[0052]
When this initialization process is completed, the code input is substituted for K (step S402), and an input code determination process for determining whether this K is the numerical code P or the state code Q (step S403). To do. As a result, if it is determined that the code is a numerical code (Yes at Step S403), a numerical value restoring process (Step S404) is performed to restore the code stored in K to a numerical value and store it in L, and the state identifying process The process proceeds to (Steps S405 to 407).
[0053]
Specifically, it is confirmed whether or not the state value S is 0 (step S405), and when the state value S is 0 (step S405 affirmative), the process corresponding to S0, that is, restored to A The run length value L is stored (step S408), the next code unit is input and stored in K (step S409), the code stored in K is restored to a numerical value, and stored in L ( In step S410), the process stores the value of L in B (step S411), and outputs a set of run length values in which A is output X and B is output Y (step S414).
[0054]
When the state value S is not 0 (No at Step S405), it is confirmed whether or not the state value S is 1 (Step S406). When the state value S is 1 (Yes at Step S406). , The process corresponding to S1, that is, the process of storing the L value in B (step S412), is output as a set of run length values in which A is output X and B is output Y (step S414).
[0055]
Further, when the state value S is not 1 (No at Step S406), it is confirmed whether or not the state value S is 2 (Step S407). When the state value S is 2 (Yes at Step S407). , The process corresponding to S2, that is, the process of storing the L value in A (step S413), is output as a set of run length values in which A is output X and B is output Y (step S414).
[0056]
If the status value S is not 2 (No at step S407), the process corresponding to S3 is performed. Specifically, the L value is stored in N as an initial value (step S417), and then output as a set of run length values in which A is output X and B is output Y (step S418), and N is decremented. After this (step S419), if the value of N is not 0 (No at step S420), the process proceeds to step S418 and the process is repeated. Then, when the value of N becomes 0 (Yes at Step S420), an end determination is made (Step S421), and when it does not end (No at Step S421), the process proceeds to Step S402.
[0057]
If it is determined in step S403 that the code is a numerical code (No in step S403), the code stored in K is restored to the state value and stored in S (step S415). It is confirmed whether or not there is (step S416). As a result, when S is 3 (Yes at Step S416), the process proceeds to Step S414, and when S is not 3 (No at Step S416), the process proceeds to Step S421.
[0058]
By performing the above series of processing, when the state code is input and restored to the predetermined state value S, when this S is in the state of S3, a set of run length values is omitted. A set of run length values stored in A and B can be output without waiting for the input of a numerical code.
[0059]
In addition, when this S value is S0 when a numerical code is inputted and restored to a predetermined numerical value and stored in L, a set of run length values is encoded into a set of numerical codes. Therefore, a set of run length values is output using the value stored in L and the value obtained by decoding the next numerical code.
[0060]
When the S value is S1, the numerical code for the continuous number of 0 is omitted, so that a set of run length values is output using the value stored in A and the restored numerical value L. If the S value is S2, the numerical code for the continuous number of 1 is omitted, so that a set of run length values is output using the value stored in B and the restored numerical value L. Do it.
[0061]
Further, when this S value is S3, the restored numerical value is the number of iterations N, and N sets of run length values are omitted, so the values stored in A and B at that time are used. Repeat the output operation of a set of run length values for the number of times. For this reason, the original run-length sequence can be decoded from the code sequence data generated by the data encoding procedure shown in FIG.
[0062]
When the above processing procedure is realized by software, an appropriate memory may be allocated to X, Y, A, B, S, T, K, L, and N. It is desirable to use it for improving the processing performance. The constant C and each control can be realized by describing them as a program, that is, an instruction code.
[0063]
Further, some of the series of processes described above can be omitted. For example, N for counting and storing the number of iterations and L for storing the restored numerical value can also be omitted. It is also possible to substitute one of X and Y for storing the output run length value.
[0064]
Further, in the above series of explanations, for the convenience of explanation, detailed explanations about the run-length numerical value output (steps S414 and S418) and the data end determination (step S421) related thereto are omitted.
[0065]
Next, the code set used for the data encoding process and the data decoding process shown in FIGS. 2 and 4 will be described. FIG. 5 is an explanatory diagram illustrating an example of a code set used for the data encoding process and the data decoding process illustrated in FIGS. 2 and 4.
[0066]
As shown in the figure, the code set used in the present embodiment is composed of six types of code units of 1st to 6th. Specifically, the first code format P1 to the third code format P3 are: A numerical code P indicating a numerical value, and a fourth code format Q1 to a sixth code format Q3 are state codes Q indicating state values.
[0067]
Here, the first code format P1 has a 4-bit width and is identified using the fact that the 4-bit numerical value is less than “10”, and is a value obtained by adding 1 to the numerical value. Corresponds to the numerical value L. The second code format P2 has an 8-bit width and is identified by the value of the upper 4 bits preceding in the code string being “11” or “12”. A value obtained by adding 11 ″ corresponds to the numerical value L.
[0068]
The third code format P3 is at least 8 bits wide and has a bit width that is a multiple of 4 and is identified by the value of the preceding 4 bits in the code string being “12”. For these 4 bits, the value obtained by adding “43” to the numerical value obtained by concatenating the lower 3 bits of 4 bits upward (connected) until a numerical value of “8” or more is detected corresponds to the numerical value L. To do.
[0069]
The fourth code format Q1 has a 4-bit width, is identified by the 4-bit numerical value being “13”, and the lower two bits of the value obtained by adding “1” to the previous state value are new. Corresponds to the state value. The fifth code format Q2 has a 4-bit width, is identified by the 4-bit value being “14”, and the lower 2 bits of the value obtained by adding “2” to the previous state value are new. Corresponds to the state value. The sixth code format Q3 has a 4-bit width, is identified by the 4-bit value being “15”, and the lower 2 bits of the value obtained by adding “3” to the previous state value are new. Corresponds to the state value.
[0070]
Although the state value can take four values, the state code is generated only when the state value changes. Since there are only three transition objects from one state value to another state value, the number of state codes is reduced to three.
[0071]
In addition, in the numerical code P, the code whose value is “0” is not clearly shown, but it is desirable to express “0” using a conversion procedure described later. However, this code format does not limit the range that can be expressed in principle, and it should be noted that an arbitrary integer can be expressed when the third code format P3 is used. This is because the temporary storage used for the process of restoring the numerical value has a finite bit width, but since there is no restriction on the length of the P3 code, the result of processing by concatenation and addition becomes '0' or This is because a negative sign can be generated.
[0072]
Next, input code type determination, state coding control, state restoration processing, numerical value coding processing, and numerical value restoration processing when the code set shown in FIG. 5 is used will be described. First, in the determination of the input code type (corresponding to step S403 in FIG. 4), if the value of the upper 4 bits preceding the code is a value equal to or less than “12”, it is determined that the code is a numerical code. In this case, it can be determined that it is a status code.
[0073]
6 is a flowchart showing a state encoding control procedure when the code set shown in FIG. 5 is used. FIG. 7 shows a state decoding control procedure when the code set shown in FIG. 5 is used. It is a flowchart. In the figure, “K (n) ← numerical value” means that the lower n bits of the numerical value on the right side are output as a code, and “W” is a working memory used for the calculation.
[0074]
As shown in FIG. 6, when state encoding is performed, a value obtained by subtracting the previous state value T from the state value S and “3” are logically ORed for each bit, and “12” is added to this. The value is stored in the working memory W (step S601), and the lower 4 bits of the working memory W are output as a 4-bit code K (step S602).
[0075]
As shown in FIG. 7, when state decoding is performed, a value obtained by subtracting “12” from the code value is changed to the state value S so far in response to the generation of any of the codes Q1 to Q3. Addition is performed, and a logical product for each bit of the resultant value and the constant value '3' is obtained and stored in the state value S as a new state value (step S701).
[0076]
By performing the control shown in FIGS. 6 and 7, it is possible to generate a predetermined state code and restore the state value using the state code. For example, when the state value T immediately before encoding is “0” and the new state value S is “3”, “ST” is “3”, so this value and the constant value “3”. The logical product for each bit of “3” is “3”. Then, “15” obtained by adding “12” to this value, that is, a Q3 code is generated. On the other hand, when restoring the state code, “K-12” becomes “3”, and the value “3” obtained by adding the previous state value “0” to this value and the constant value “3” for each bit. When the logical product is taken, “3” becomes a new state value S, and it can be seen that it is correctly restored.
[0077]
When the state value T immediately before encoding is “3” and the new state value S is “0”, “ST” becomes “−3”, and this value and the constant value “3”. Since the logical product for each bit of “1” is “1”, “13” obtained by adding “12” to this value, that is, the Q1 code is generated. On the other hand, when restoring the state code, “K-12” becomes “1”, and the value “4” obtained by adding the previous state value “3” to this value and the constant value “3” for each bit. When the logical product is taken, “0” becomes a new state value S, and it is understood that the state is correctly restored.
[0078]
FIG. 8 is a flowchart showing a numerical encoding control procedure when the code set shown in FIG. 5 is used, and FIG. 9 shows a numerical decoding control procedure when the code set shown in FIG. 5 is used. It is a flowchart. In the figure, “K (n) ← numerical value” means that the lower n bits of the numerical value on the right side are output as a code, and “W” is a working memory used for the calculation.
[0079]
As shown in FIG. 8, here, the numerical value “V” to be encoded is converted into one of codes P1 to P3 and output. As already mentioned, since the sign of the value “0” is not defined in this numerical code P, here, when “V = 0”, it is converted into a constant value “Z”. Zero value conversion processing is performed. That is, since the frequency of V = 0 is very low, the compression rate is improved by assigning it to a relatively long codeword. Specifically, steps S801 to S804 described below correspond to the zero value conversion process, and steps after step S805 correspond to a process of generating a code word from a numerical value.
[0080]
As shown in the figure, first, it is determined whether or not the encoding target value V is equal to or greater than a constant value Z (step S801). If it is equal to or greater than Z (Yes in step S801), the value of V is set. Increment (step S802). If it is not equal to or greater than Z (No at Step S801), it is determined whether V is 0 (Step S803). If Z is 0 (Yes at Step S803), the constant value Z is stored in V (Step S803). S804).
[0081]
When the zero-value conversion process is finished, it is determined whether or not the current encoding target value V is “10” or less (step S805). (Yes in step S805), the lower 4 bits of the value obtained by subtracting “1” from V are output as a code (step S806), and the numerical encoding ends.
[0082]
On the other hand, if V is not "10" or less (No in step S805), it is determined whether or not this V is "42" or less (step S807). If V is "42" or less (step S807). (Yes) The lower 8 bits of the value obtained by adding “149” to V are output as a code (step S808), and the numerical encoding is terminated. Since the definition of the P2 code is “K (8) ← 160 + (V−11)”, that is, “K (8) ← V + 149”, the code generated here is nothing but the P2 code. Since “160” is expressed as a binary number “10100000”, the upper 3 bits are a code-specific constant.
[0083]
If it is determined in step S807 that V is not equal to or lower than “42” (No in step S807), a 4-bit code having a value of “12” is first output as the start identification code of the P3 code ( Step S809). Thereafter, a value obtained by subtracting “43” from V is stored in the work memory W (step S810), and it is checked whether or not the value of W is less than “8” (step S811).
[0084]
If the result is “8” or more (No at step S811), the lower 3 bits of the W value are output as a 4-bit code (step S812), and the W value is shifted to the right by 3 bits. After the code output portion is cut off (step S813), the process returns to step S811.
[0085]
On the other hand, if it is less than “8” (Yes at step S811), a value obtained by adding “8” to the W value is output as a 4-bit code (step S814), and numerical encoding is terminated. . Since the constant “7” is expressed as a binary number “0111”, the code generated in step S812 is always a numerical value of “8” or more, and it can be clearly shown that this code is the last one in the numerical part. It can be seen that this code is nothing but the P3 code.
[0086]
As shown in FIG. 9, when performing numerical value restoration, a code string encoded in any one of the code formats P1 to P3 is sequentially read in units of 4 bits, and the numerical value is restored to the working memory W. . Note that the notation “K ← sign input” means that a 4-bit code is input to K as a numerical value. In addition, here, “0 value reverse conversion processing” which is reverse conversion of the 0 value conversion processing shown in FIG. 8 is performed. Steps S901 to S911 shown below correspond to a numerical value restoration process, and steps after step S912 correspond to a zero value reverse conversion process.
[0087]
As shown in the figure, when performing numerical value restoration processing, first the first 4 bits of the code are input to K (step S901), and it is determined whether or not the K value is less than “10” (step S901). Step S902). If the K value is less than “10” (Yes at Step S902), a value obtained by adding “1” to the K value is stored in W as a restored numerical value (Step S903), and 0 value reverse conversion described later is performed. Transition to processing. Since the code in which the first 4 bits are less than “10” is nothing but the P1 code, it can be restored to a numerical value by adding “1” to this K value.
[0088]
On the other hand, when the K value is not less than “10” (No at Step S902), it is determined whether or not the K value is “12” (Step S904). In step S904, the value obtained by shifting the K value to the left by 4 bits is stored in W, the next 4 bits of the sign are input to K, and "149" is calculated from the value obtained by adding W and the new K value. After the subtracted value is stored in W as a restored numerical value (step S905), the process proceeds to 0 value reverse conversion processing described later.
[0089]
On the other hand, when the K value is “12” (Yes at Step S904), since the code is nothing but a P2 code having an 8-bit length, the value of W is initialized to “0” (Step S906). The next 4 bits of the code are input to K (step S907), the K value is added to W (step S908), and it is determined whether the K value is less than '8' (step S909).
[0090]
As a result, if the K value is less than '8' (Yes at Step S909), the sign of the numerical value part continues thereafter, so after shifting the value of W to the left by 3 bits (Step S910), the above Step S907 Migrate to
[0091]
On the other hand, if the K value is not less than “8” (No at Step S909), the value obtained by adding “35” to the previous W is newly stored in W (Step S911), and the zero-value inverse conversion process is performed. Migrate to In the P3 code, a value obtained by adding “43” to a numerical value obtained by concatenating the lower 3 bits of 4 bits upward (connected) until a value of “8” or more is detected as the 4 bits. Corresponding to Then, since “8” indicating the end of the numerical value part is added to the value of K when a numerical value of “8” or more is detected, “35” which is “43-8” here. Is added.
[0092]
Thereafter, a zero value reverse conversion process for restoring the zero value conversion process is performed. Specifically, it is confirmed whether or not the restored numerical value W is larger than the constant Z (step S912). If the restored numerical value W is larger than Z (step S912 affirmative), from W to “1”. The value obtained by subtracting 'is stored in W (step S913), and the numerical value restoring process is terminated.
[0093]
On the other hand, when the numerical value W is equal to or smaller than Z (No at Step S912), it is confirmed whether or not the restored numerical value W matches the constant Z (Step S914). (Yes in S914), “0” is substituted for W (step S915), and the numerical value restoring process is terminated.
[0094]
As described above, in this embodiment, one of the states S0 to S3 is based on the 0-bit continuous number X, the 1-bit continuous number Y, the value A immediately before X, and the value B immediately before Y. The state value is S, the value immediately before S is T, and when a mismatch event occurs, a state code Q indicating the value of the state value S is generated. When X ≠ A, a numerical code P indicating the value of X is generated, and when Y ≠ B, a numerical code P indicating the value of Y is generated and a regression event occurs. In this case, since the numerical code P indicating the value of the repetition number N is generated prior to the generation of the state code, the pseudo halftone image data generated by the error diffusion process by software processing by the microprocessor. Can also be compressed efficiently.
[0095]
【The invention's effect】
  As described above, according to the invention of claim 1,In the calculation of the state value corresponding to the data of the input unit, the number of consecutive 0 bits X, the number of consecutive 1 bits Y, the number of consecutive 0 bits A immediately before, and the number of consecutive 1 bits B immediately preceding When X ≠ A and Y ≠ B, the value of the state S0 is the state value S. When X = A and Y ≠ B, the value of the state S1 is the state value S, and X ≠ A and The value of the state S2 is set as the state value S when Y = B, and the value of the state S3 is calculated as the state value S when X = A and Y = B. Is the state S3, and the state value S and the previous state value T are equal coincident events, this is regarded as a repetitive event, and the repetitive number N in which the repetitive event occurs continuously is calculated. When a repetitive event occurs, the status value S and the previous status value T are different from each other, or the input is completed. When a mismatch event occurs, a status code indicating the value of the status value S is generated. When the generation of the status code ends or a match event occurs, the number of consecutive 0 bits X Alternatively, a numerical code indicating the value of the consecutive number Y of 1 bits is generated, and when a regression event occurs, the numerical code indicating the value of the iteration number N is generated prior to the generation of the state code. Using the concept of event, discrepancy event, repetitive event, and regression event, data can be efficiently compressed even for pseudo halftone image data generated by error diffusion processing.There is an effect that a possible data encoding method can be obtained.
[0098]
  Claims2According to the invention, when encoding is started, predetermined initial values are stored in T, A, B and the number of repetitions N, respectively, and X and YTo laThe length value is input, and after this input, the state value S is generated, the occurrence of the coincidence event or the disagreement event is determined corresponding to the generated state value S, and the occurrence of the repetitive event is generated in response to the occurrence of the coincidence event Determine the presence or absence, add the number of iterations in response to the occurrence of a repetitive event, determine the presence or absence of a regression event in response to the occurrence of a discrepancy event or the end of data to be encoded, and In response, an iteration number numerical code indicating the value of the iteration number N is generated. After the iteration number numeric code is generated, the iteration number N is returned to a predetermined initial value, and in response to the occurrence of a mismatch event or the initialization of the iteration number N. A state code expressing the value of the state value S is generated, and after generation of the state code or determination of occurrence of a repetitive event, if X does not match A, a numerical code corresponding to X is generated, and Y is B If it does not match, generate a numeric code corresponding to Y Since the contents of A are updated to X, the contents of B are updated to Y, and the contents of T are updated to S after the generation of the numerical code or the addition of the number of iterations N, the software processing by the microprocessor is performed. There is an effect that a data encoding method capable of compressing suitable data can be obtained.
[0099]
  Claims3According to the invention, when starting decoding, the storage unit S that stores the restored state value, the storage unit C that stores the value corresponding to the X among the restored run-length values, and the restored A predetermined initial value is substituted into a storage unit D for storing a value corresponding to Y among the run length values, and a predetermined code unit is input, so that the code is a numerical code P or a state code Q If it is determined to be a numerical code, the code is restored to a numerical value and stored in the storage unit L. If it is determined to be a state code, the code is restored to a state value to S The state value S at the time when the restored numerical value is stored and stored in L is the state S0 where X ≠ A and Y ≠ B, and the states S1 and X where X = A and Y ≠ B Neither state S2 in the relationship of ≠ A and Y = B or state S3 in the relationship of X = A and Y = B When a new state value is stored in S, it is determined whether or not the value of S matches S3, and when the value of S is identified as S0, After the value of L is stored in C, the next numerical code is input and restored and stored in D. When the value of S is identified as S1, the value of L is stored in D and the value of S Is determined to be S2, the value of L is stored in C, and when updating is completed or when it is determined that the value of S matches the state value S3, a set of values of C and D is set. When the S value is identified as S3, the C and D values are output as a set of run length values for the number of times corresponding to the L value. Data that can efficiently restore a compressed halftone image data generated by error diffusion processing. Decoding method an effect that can be obtained.
[0100]
  Claims4According to the present invention, claims 1 to3By recording a program that causes a computer to execute the method described in any one of the above, the program can be machine-readable, and thereby3There is an effect that a recording medium capable of realizing any one of the above operations by a computer can be obtained.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram for explaining the concept of a data encoding method and a data decoding method according to an embodiment of the present invention;
FIG. 2 is a flowchart showing an encoding procedure used in the present embodiment.
FIG. 3 is a flowchart showing a non-output N encoding procedure shown in steps S209 and S219 of FIG. 2;
FIG. 4 is a flowchart showing a data decoding procedure according to the present embodiment.
FIG. 5 is an explanatory diagram illustrating an example of a code set used for the data encoding process and the data decoding process illustrated in FIGS. 2 and 4;
6 is a flowchart showing a state encoding control procedure when the code set shown in FIG. 5 is used.
7 is a flowchart showing a state decoding control procedure when the code set shown in FIG. 5 is used.
FIG. 8 is a flowchart showing a numerical encoding control procedure when the code set shown in FIG. 5 is used.
9 is a flowchart showing a numerical decoding control procedure when the code set shown in FIG. 5 is used.
[Explanation of symbols]
Number of consecutive X 0
Number of consecutive Y 1
A Previous X value
B Y value just before
S state value
T S value just before
N, P, P1, P2, P3 Numerical code
Q, Q1, Q2, Q3 Status code

Claims (4)

The Ranrengu scan value sequence obtained by scanning the data sequentially inputs a set of the number of bit continuations and bit number of consecutive 1 0 as an input unit, there in data encoding method for converting into a predetermined code sequence And
As the calculation of the state value corresponding to the data of the input unit, the number of consecutive 0 bits X, the number of consecutive 1 bits Y, the number of consecutive 0 bits A immediately before, and the number of consecutive 1 bits immediately preceding 1 When B is in the relationship of X ≠ A and Y ≠ B, the value of the state S0 is the state value S, and when X = A and Y ≠ B, the value of the state S1 is the state value S, and X A calculation step of calculating the value of state S2 as state value S when ≠ A and Y = B, and calculating the value of state S3 as state value S when X = A and Y = B;
When the immediately preceding state value T is the state S3 and the state value S and the immediately preceding state value T are the same coincidence event, this is regarded as a repetitive event, and the repetitive event occurs continuously. An iterative number calculating step for calculating an iterative number N, and a regression event determination for determining a regression event when the state value S and the immediately preceding state value T are different from each other after the occurrence of the repetitive event or when the input is completed A state code generation step of generating a state code indicating the value of the state value S when the mismatch event occurs, and generation of the state code by the state code generation step ends or the match event occurs A first numerical code generation step for generating a numerical code indicating a value of the continuous number X of 0 bits or the continuous number Y of 1 bits, and when the regression event occurs, the state Depending on the code generation process A state code corresponding to the data of the input unit, including a second numerical code generation step for generating a numerical code indicating the value of the repetition number N calculated by the repetition number calculation step prior to the generation of the state code And a generation process for generating a numerical code,
Data encoding method characterized by including the. The calculation step, when starting the encoding, T, A, B and the initialization step of storing a respective predetermined initial value to the number of iterations N, the input step of inputting the run-length value in the X and Y And a state value generation step of generating the state value S after input by the input step,
The generation step includes a matching event determination step for determining the occurrence of the coincidence event or the mismatch event corresponding to the state value S generated by the state value generation step, and the repetitive event in response to the occurrence of the coincidence event. A repetitive event determining step for determining whether or not the occurrence of the repetitive event, a repetitive number adding step for adding the repetitive number in response to the occurrence of the repetitive event, and a response to the occurrence of the mismatch event or the end of the encoding target data A regression event determining step for determining whether or not the regression event has occurred, an iteration number numerical code generating step for generating an iteration number numerical code indicating the value of the iteration number N in response to the occurrence of the regression event, and the iteration The value of the state value S is expressed in response to a regression process for returning the iteration number N to a predetermined initial value after generation of a numerical value code, and the occurrence of the mismatch event or the initialization of the iteration number N by the regression process. Status mark And a numerical code corresponding to X when X does not match A after the generation of the state code by the state code generation step or the determination of the occurrence of the repetitive event by the repetitive event determination step A numerical code generation step for generating a numerical code corresponding to Y when Y does not match B, and generation of a numerical code by the numerical code generation step or repetition number N of the repetition number addition step after the addition, it updates the contents of the a to X, updates the contents of the B to Y, wherein the content of the T to claim 1, characterized in that it includes a value just before the update step of updating the S Data encoding method. In the code string data type the code string obtained by scanning a number of bit continuations of 0 X and data decoding method for restoring output Ranrengu scan value string to set the unit of one of the number of bit continuations Y There,
When starting decoding, the storage unit S that stores the restored state value, the storage unit C that stores the value corresponding to the X among the restored run-length values, and the run-length value that is restored An initialization step of initializing by substituting a predetermined initial value in the storage unit D for storing a value corresponding to Y;
An input code type determination step of inputting a predetermined code unit and determining whether the code is a numerical code P or a state code Q;
A numerical code restoring step of restoring the code to a numerical value and storing it in the storage unit L when it is determined as a numerical code by the input code type determining step;
A state code restoration step of restoring the code to the state value and storing it in the S when the input code type determination step determines that the state code;
The value of the state value S when the restoration numerical value is stored in the L is the state S0 in the relationship of X ≠ A and Y ≠ B, the state S1 in the relationship of X = A and Y ≠ B, and X ≠ A And state S2 in the relationship of Y = B or state S3 in the relationship of X = A and Y = B (where A is the number of consecutive 0 bits immediately before and B is the number of consecutive 1 bits immediately preceding An identification step for identifying whether the
A S3 state determination step of determining whether or not the value of S matches S3 when a new state value is stored in S;
If the value of S is identified as S0 by the identification step, the value of L is stored in the C, the next numerical code is input and restored, and stored in the D Run value update process,
A second run value updating step of storing the value of L in D when the value of S is identified as S1 by the identification step;
A third run value updating step of storing the value of L in the C when the value of S is identified as the S2 by the identifying step;
The values of C and D when the update by the first, second or third run value update process is completed or when it is determined by the S3 state determination process that the value of S matches the state value S3 A first output step for outputting as a set of run length values;
A second output that outputs the C and D values as a set of run length values for the number of times corresponding to the L value when the S value is identified as S3 by the identification step. Process,
A data decoding method comprising: A computer-readable recording medium having recorded thereon a program for causing a computer to execute the method according to any one of claims 1 to 3 .

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