JP2506794B2 - Decryption processing method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a decoding processing method for data obtained by coding an image or the like.

2. Description of the Related Art Run length encoding is often performed when encoding data such as images. This encodes not the bit pattern itself to be encoded, but the number of times the same attribute (for example, black and white) continues. FIG. 2 shows an example of run length coding. Assuming that the 24 bit bit pattern to be encoded is as shown in (a), 0
Alternatively, a portion in which only one of 1 is continuous is called a run. The bit length (run length) of each one run is counted as shown in (b). This value is converted into a binary number as shown in (c), which means that the original 24-bit data can be encoded into the 14-bit run length data. The fitting method (code table) for converting the value of the run length data (b) into the code bit pattern (c) includes simple binary expression,
Various methods have been considered.

Further, in order to improve the compression rate, the value of the pixel to be coded is predicted from the known (already coded) surrounding pixels, and the error is subjected to the run length coding [eg Mizuno]. Iinuma: "Coding of Halftone Facsimile Signals", IEICE Technical Report, CS79-176 (1979)]. FIG. 3 shows an example of the application of the encoding method using both the prediction of the pixel value and the run length encoding to a binary image. In FIG.
For the original data as shown in (a), the prediction data as shown in (b) (for example, the bit pattern data of the previous line in the image) is prepared, and the prediction match is set to 0 and the mismatch is set to (a) and (b). ) Error data (c), and (d)
The run length coding is performed as follows.

The code generated in this way is decoded as follows.

(1) The run length of error data is reproduced.

(2) This run length data is converted into a bit pattern by setting 0 for a prediction matching run and 1 for a mismatching run (whether the first data indicates prediction matching / mismatching, that is, 0).
It must be given in advance).

(3) The prediction data prepared in advance is compared with this bit pattern (error data), and if the bit is 0, the prediction data itself is used. If the bit is 1, the inverted prediction data is the original data. It is adopted as the corresponding bit of.

(4) In the same manner, the original data is sequentially reproduced.

FIG. 7 shows a block diagram of the above decoding processing, and FIG. 8 shows the flow of one decoding processing. In FIG. 7, the error bit pattern creation unit 21 receives run length data for a run to be decoded, and outputs a bit data string of 0 (prediction match) or 1 (mismatch) of the length of the number represented by the data. appear. This value 0 or 1 (that is, prediction match or mismatch) alternates with each run. The original data bit reproduction unit 22 reproduces the original data using the data from the error bit pattern creation unit and the data from the prediction data creation unit 24, and writes it in the memory unit 23. The predicted value creation unit 24 creates a predicted value of new reproduction data based on the data in the memory unit 23.

Problems to be Solved by the Invention In the above-described encoding method, if the prediction method of each bit is appropriate, the occurrence of prediction mismatch data (1 in the above example) is rare, and most of them are predicted. It becomes the data of agreement. However, in the conventional decoding method, the same processing is performed for each of the predictive coincidence code and the non-coincidence code, and the same number of processes as the number of codes (the number of changes of error data bits) are required.

The present invention has been made in view of such drawbacks, and an object thereof is to reduce the number of decoding processes.

MEANS FOR SOLVING PROBLEMS The present invention provides run length data n (natural number) of predicted coincident runs.
Assuming that the next prediction-mismatch run length is 1, the prediction-matching run of length n and the prediction-mismatching run of length 1 are used as one processing unit to perform pixel reproduction at once. When the run length m (natural number) of the code of the next prediction disagreement is not 1, there is provided means for performing pixel reproduction of the prediction disagreement run of length m-1.

Action In the present invention, it is assumed that the run length of the next prediction disagreement is 1 when the run length data of the prediction coincidence run is obtained, and the length n
Pixel reproduction is performed at one time by using the prediction coincidence run and the prediction non-coincidence run of length 1 as one processing unit, and the pixel reproduction of the prediction non-coincidence run is performed only when the run length of the code of the next prediction non-coincidence is not 1.

Embodiment FIG. 1 shows a flow chart of an embodiment of the present invention.

FIG. 1 shows processing of a predicted match run length n and a predicted mismatch run length m, both of which are natural numbers. First, when the value n of the predicted match run length is received, prediction is performed on (n + 1) pixels. Next, the color is inverted only for the last pixel of the (n + 1) pixels. this is,
This is because it is determined that this pixel does not match the prediction. Next, the value m of the prediction disagreement run length is received. If this is 1, this process is terminated. Only when this value is not 1, the prediction data is created for (m-1) pixels, the color of this pixel is inverted, and the series of processes is ended. As described above, the process is completed for the n prediction matching pixels and the m prediction mismatch pixels totaling n + m pixels. Since the predicted coincidence run length value is naturally received for the next pixel, the process of this drawing may be similarly performed from the beginning.

 A block diagram of another embodiment of the present invention is shown in FIG.

In FIG. 9, the data transfer control unit 11 receives the run length data and the prediction match / mismatch information, sends the run length data to the error bit pattern creating unit 12 in the case of the prediction match, and the mismatch run length in the case of the mismatch. Send to the determination unit 16. The error bit pattern creating unit 12 creates an error bit pattern consisting of 0s (representing prediction matching bits) and 1s (representing prediction mismatch bits) as many as the received run length data, and the original data bit reproducing unit Send to 13. Based on the data created by the prediction data creation unit 14, the original data bit reproduction unit 13 reproduces the bit having the error data bit of 0 as the prediction data (that is, as the prediction match), and the error data bit of 1 For a bit, the prediction data is inverted (prediction mismatch) and reproduced. These reproduced bits are stored in the memory unit 15. The prediction data creation unit 14 creates prediction data by using the data of the reproduced memory unit 15. On the other hand, the mismatch run length determination unit 16 does nothing if the received mismatch run length is 1, and sends the run length data to the error bit pattern creation unit 17 only when the received mismatch run length exceeds 1. The error bit pattern creating unit 17 generates (run length sent from the mismatch run length determining unit 16) -1 error bit (value is 1) and sends it to the original data bit reproducing unit 13. The original data bit reproduction unit 13 reproduces the original data using the error bit pattern and the prediction data from the prediction data creation unit 14, and reproduces the bit to be written in the memory unit 15.

The above operation will be specifically described by taking the decoding of the code used in FIG. 3 as an example. FIG. 4 shows the length n in this embodiment.
FIG. 6 is a diagram showing a flow of a decoding process for the prediction matching run of FIG. In the example of FIG. 3, the error data begins with a predictive match. First, 3 is obtained as the run length of the error data. Since this is the run length related to the prediction match, the data transfer control unit 11
Sends data of 3 to the error bit pattern creating unit 12. The error bit pattern creation unit 12 creates a bit pattern of three 0s and one 1, that is, 0,0,0,1 based on this data, and sends this bit pattern to the original data bit reproduction unit 13. In the original data bit reproduction section 13, this bit pattern and the data 0,0,0,1 from the prediction data creation section 14
Then, the original data 0,0,0,0 is reproduced and written in the memory section 15 to complete one processing (see FIG. 4). Next, the processing when the run length of the error data is 1 is performed. FIG. 5 is a diagram showing the flow of the decoding process for a run of length 1 with a prediction mismatch in this embodiment. The mismatch run length (value is 1) of the error data given here is the data transfer control unit 11
Is sent to the non-matching run length determining section 16, but this value is detected to be 1, and the processing relating to the run length of the prediction mismatching is ended without performing any processing on the memory section (see FIG. 5). ). Next, the prediction matching error data (value is 6) is given again, and the decoding process is performed. Similarly, the processing proceeds in the order of 1 (prediction mismatch) and 4 (match) of the run length data. Next, the flow of processing when run length data (value is 2) that does not match prediction is given will be described next. Sixth
The figure is a diagram showing the flow of the decoding process of the present embodiment for such a prediction mismatch run having a length m exceeding 1. First, the data transfer control unit 11 sends this data to the mismatch run length determination unit 16. Since this value is 2, this data is sent to the error bit pattern creation unit 17. The error bit pattern creating unit 17 reproduces the error bit pattern of 2-1 = 1 bit (that is, 1), and the data is sent to the original data bit reproducing unit 13. In the original data bit reproducing section 13, the original data of 1 is reproduced from the sent error bit pattern and the same 1-bit prediction data (value is 0) from the prediction data creating section 14, and the memory section
It is written in 15 (see FIG. 6). After that, the processing of the run length data of the prediction match is executed again in the same manner.

EFFECTS OF THE INVENTION According to the present invention, the pixel reproduction process for a single prediction mismatch run of length 1 is eliminated, and the number of processes is reduced as a whole.

[Brief description of drawings]

FIG. 1 is a flow chart showing an embodiment of the present invention, FIG. 2 is a principle diagram of run length coding, FIG. 3 is a principle diagram of run length coding using prediction data, and FIG. In one embodiment, a processing flow chart for a prediction match run of length n, FIG. 5 is a processing flow chart for a prediction mismatch run of length 1 in the same embodiment, and FIG. 6 is a prediction mismatch for length m in the same embodiment. FIG. 7 is a block diagram showing a conventional decoding method, FIG. 8 is a flowchart showing a conventional decoding process, and FIG. 9 is a block diagram showing another embodiment of the present invention. Is. 11 ... Data transfer control unit, 12 ... Error bit pattern creation unit, 13 ... Original data bit reproduction unit, 14 ... Prediction data creation unit, 15 ... Memory unit, 16 ... Mismatch run length determination unit,
17 ... Error bit pattern creation unit.

Claims (1)

(57) [Claims] 1. A color of a pixel to be coded is predicted from the color (white or black) of pixels around the pixel to be coded, and whether or not the predicted value matches (hits) the color of the actual pixel (whether or not). (Miss) bit information about the run is concatenated with the run length to perform coding, and the next prediction mismatch run is obtained when the run length data n (natural number) of the prediction match run is obtained in the decoding of the code generated by the coding method. Assuming that the length is 1, pixel prediction is performed at one time using a prediction-matching run of length n and a prediction-mismatching run of length 1 as one processing unit, and the run length m (natural number) of the prediction-mismatching code is If it is not 1, a decoding processing method is characterized in that pixel reproduction of a prediction mismatch run of length m-1 is performed.