JPH0683377B2 - Run length counter - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a run length counting device in a run length coding system.

2. Description of the Related Art A run length counting device in a run length encoding system of this type in the related art determines the number of consecutive bits of only white (for example, "0") or the number of consecutive bits of only black (for example, "1") of an image. , Run length was used and the method of counting was adopted.

For example, as shown in FIG. 3 (a), in the case of an image of a bit string in which the frequency of occurrence of bit "1" is low with respect to bit "0" and bit "1" does not continue, run The length is counted as 2 bits, 1 bit, 3 bits ... As shown in FIG.

Further, in the case of an extreme bit string in which bit "0" and bit "1" are alternately repeated as shown in FIG. 3 (b), the run length is counted bit by bit.

Problems to be Solved by the Invention As described above, in the case of the conventional run-length counting device, depending on the type and characteristics of the image, for example, FIG.
As shown in FIG. 3B, the run length delimiter becomes short, the number of codes to be allocated increases, which may be disadvantageous for compression coding. In the extreme case as shown in FIG. 3B, the run length is bit by bit. Since this is counted, there is a problem that the compression rate is significantly reduced when this is encoded, which is extremely disadvantageous in compression encoding.

Therefore, the present invention has been made in view of the circumstances as described above, and by changing the conventional definition of run length and setting and counting the definition of run length that is advantageous for compression encoding. SUMMARY OF THE INVENTION It is an object of the present invention to provide a run-length counting device capable of improving compression encoding and / or compression efficiency.

Means for Solving the Problems In order to achieve the above object, the run length counting apparatus according to the present invention uses the run length as the number of black (white) bits before the occurrence of white (black) bits of an image, It is characterized in that it is counted as the number of bits to which the white (black) bits are added.

Operation With the above configuration, the run length delimiter becomes long and the number of codes to be allocated is small, which is very advantageous for compression encoding.

Examples Hereinafter, the present invention will be described with reference to the drawings. FIG. 1 is a schematic block diagram showing an embodiment of a run length counting apparatus showing an embodiment of the present invention, and FIGS. 2 (a) to 2 (d) are various bit strings in the run length counting apparatus of the present invention. It is explanatory drawing which shows the example of run length division.

In the present invention, according to the type and characteristics of an image, for example, the number of black (“1”) bits (including the case of zero) before occurrence of the white (“0”) bit of the image is changed to the white ( The number of bits including "0" bits is defined as the run length, or the number of white ("0") bits before the black ("1") bit of the image occurs (including the case of zero). In addition, the number of bits to which the black (“1”) bit is added is defined as the run length, and is counted.

Therefore, according to the present invention, in the case of an image of a bit string as shown in FIG. 2 (a) (this is an image of the same bit string as in FIG. 3 (a)), the run length delimiter is shown in FIG. It becomes longer than the case of (a), which is advantageous for compression encoding.

Further, in the case of an image of a bit string as shown in FIG. 2 (b) (this is an image of the same bit string as in FIG. 3 (b)), the run length delimiter is as shown in FIG. 3 (b). It is halved, and in this case, compression coding becomes more advantageous.

If the number of white (“0”) bits before the black (“1”) bit of the image is added to the number of black (“1”) bits is defined as the run length, Needless to say, in addition to the run length delimiters shown in FIGS. 2 (a) and 2 (b), the delimiter examples shown in FIG. 2 (c) are also included.

That is, in the bit string of FIG. 2C, "1" bits are counted as one run length because the number of "0" bits before the occurrence of the "1" bit is zero. is there.

Similarly, if you define the number of black (“1”) bits before the white (“0”) bit of the image is added to the white (“0”) bit as the run length, As a matter of course, the run length delimiter example as shown in FIG. 2D is included.

Next, the configuration of this apparatus will be described with reference to FIG. In this embodiment, the number of bits obtained by adding the black (“1”) bit to the number of white (“0”) bits before the occurrence of the black (“1”) bit of the image is counted as the run length. The case will be described as an example.

The input data is image information of a bit string consisting of "0" bits and "1" bits, and the frequency of occurrence of "1" bits is extremely low.

In FIG. 1, the number of consecutive "0" bits of input data is first counted by the "0" bit counter 1. When the "1" bit is detected, the latch circuit 2 stops the operation of the "0" bit counter 1 and latches the "0" bit count value up to that point. At this time, "0" bit counter 1
The contents of are cleared in preparation for the next counting.

The latched "0" bit count value is supplied to the 1-adder 3 in the next stage, where "1" is added. That is, "1" corresponding to the detected "1" bit is added to the "0" bit count value. This is the run length.

The output (run length) from the 1 adder 3 is supplied to the code table (ROM) 4 in the next stage. In the code table 4, codes (parallel) are assigned to the run length. The assigned code is output from the code table 4 to the shift register 5 at the next stage.

The shift register 5 outputs the loaded code (parallel) as serial data. That is, compression encoding is performed.

Various timings in the device are controlled by the timing generation circuit 6.

Further, when the "1" bit is detected before the "0" bit is counted in the "0" bit counter 1,
The latch circuit 2 latches the "0" bit count value as zero, and the one obtained by adding "1" to the zero value by the 1 adder is used as the run length, and thereafter, the same processing as described above is performed.

As is apparent from the above description, the present invention is capable of selecting the run length definition according to the type and characteristics of the image and performing the run length counting based on the definition. It is also possible to implement the method in combination with conventional methods.

EFFECTS OF THE INVENTION In summary, according to the present invention, the bit number obtained by adding the white (black) bit to the number of black (white) bits before the occurrence of the white (black) bit of the image is counted as the run length. Therefore, the run length delimiter may be long and the number of the delimiters may be small, which is very advantageous for compression encoding.

[Brief description of drawings]

FIG. 1 is a schematic block diagram showing an embodiment of a run length counting apparatus according to the present invention, and FIGS. 2A to 2D are run length delimiters of various bit strings in the run length counting apparatus according to the present invention. FIG. 3 is an explanatory diagram showing an example, and FIG. 3 is an explanatory diagram showing an example of run length division of various bit strings in a conventional run length counting device. 1 ... Counter, 2 ... Latch circuit, 3 ... Adder, 4 ...
... code table (ROM), 5 ... shift register, 6 ...
... Timing generation circuit.

Claims (1)

[Claims] 1. A counter for counting the number of consecutive white (black) bits of an image, and a latch circuit for latching the count value of the counter when one black (white) bit is detected.
1 for the black (white) bit count value latched by this latch circuit
A run length counting device, comprising: