JPS63117562A - Image data coding system - Google Patents

Abstract

PURPOSE:To improve the compressing efficiency by applying the result of exclusive OR between an image data inputted sequentially at each line and an image data just before or before several lines. CONSTITUTION:An image data inputted from an input section 6 is fetched in a CPU 2 through an input control section 5 sequentially from the head by one line each. A line buffer area LA for plural lines 0 - n storing the inputted image is provided in a memory RAM 4. A data subjected to compression coding by the CPU 2 is sent to a main body such as a computer via an interface 7. Prior to apply compression coding to the data, the CPU 2 calculates an exclusive OR with the data before the line. An exclusive OR with a line just before as to the data without gradation is taken and exclusive OR is applied to the data having gradation processed by dither in matching with a period when a data with a high similarity appears so as to improve the compressing efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an image data encoding method for encoding image data.

[Prior art]

Conventionally, when sending a digitized input image to a computer or image storage device, it took a considerable amount of time due to the large amount of data, and also required a storage device with a large storage capacity. Met. Therefore, efforts have been made to reduce the amount of data by compressing the input image, thereby shortening the transfer time or reducing the storage capacity.

Increasing compression efficiency tends to make encoding/decoding more complex, but a relatively simple encoding method is one that uses run length. This is how many white dots follow the image data, then how many black dots (then...
It has the advantage that it can be decoded relatively easily without special hardware on the main body side.

However, although this method achieves high compression efficiency for data that tends to have consecutive white and black dots, it can be used to compress data that does not have many consecutive white and black points, such as data that has gradation. Data expressed using black and white dots (dither method) had the disadvantage of low compression rates.

〔the purpose〕

The present invention was made to eliminate the drawbacks of the conventional example described above, and by performing logical operations between each line before encoding, it achieves high compression efficiency despite being a simple encoding method. It became possible to obtain.

〔Example〕

The present invention will be explained below using preferred embodiments.

Figure 1 is a block diagram of the input device, where 1 is the main body of the image input device, 2 is the CPU, 3 is the memory ROM that stores instructions to control the CPU 2, and 4 is the memory RAM, which shows the image input as shown in Figure 2. A line buffer area LA for storing a plurality of lines 0 to n is provided. 6 is an input unit for reading the original image with an image sensor such as a CCD, digitizing the image data, and inputting the image data;
is its control part.

The image data inputted from the input section 6 is input to the CPU 2 through the input control section 5 one line at a time from the beginning. 7 is an interface for sending data compressed and encoded by the CPU 7 to the main body side, such as a computer.

The feature of the compression method executed by the CPU 2 of this device is that before compressing and encoding data, it calculates the exclusive OR with the data before that line, encodes the data, and sends it out. be. When the exclusive OR of two lines is calculated in this way, only the different points of the data of the two lines become 1, and the equal points become 0. Therefore 2
If two lines have a high degree of similarity, most of the points in the l-line data to be sent will be 0, and a relatively high compression rate can be obtained even if a simple encoding method such as run-length compression is used. It turns out. This exclusive OR is performed on the line, but for data that does not have a gradation, it is more efficient to perform the operation with the previous line (for data that has gradation such as dither, it is When expressed as , it is best to perform the calculation for each dither period.
When using a ×3 dither box, every 3 lines, 4
When a ×4 dither box is used, there is a strong tendency for data with a high degree of similarity to appear every four lines, so the exclusive OR may be calculated in accordance with the period.

Next, the operation of the image input device will be explained according to the operation flowchart shown in FIG. Here, it is assumed that the period is set in advance depending on the image input mode. For example, if binary data is dithered by 1.4×4, it will be set to 4.

Step S1 is initialization, and the variable i is used to count the period, and the variable l is used to count the number of lines.

In step S2, one line of image data is input from the image input section and stored in the line buffer φ. In step S3, it is determined whether the input of image data for one screen has been completed, and if the input has been completed, the process is ended. If data has been input, it is determined in step S4 whether exclusive OR with other lines should be performed. This judgment is made because if the period is 1, no calculation is performed on the first 1 line, and when the period is 4, no calculation is performed on the first 4 lines. If the exclusive OR is not performed, steps S5 to S86 are executed to store the image data of the line stored in the line buffer φ in the line buffer i that stores the i-th line, and to store the image data in the line buffer φ. Run-length encodes the image data that is stored and sends it out.

On the other hand, for lines that require an exclusive OR, the exclusive OR of the image data previously stored in the line buffer i and the image data stored in the line buffer φ is calculated in step S7. Store in line buffer l. Next, in step S8, the data after the calculation is run-length encoded and sent. and step S
At step 9, the line data stored in the line buffer φ is saved in the line buffer i.

In steps S], , O, the period counter i and the line counter l are incremented by one. In steps Sll and s12, the value of l is set to repeat within a cycle.

By decoding the data sent to the main unit in this way and similarly calculating the exclusive OR, a completely input image can be restored.

Further, when a mixture of encoded data and non-encoded data is transmitted in this manner, a command indicating the encoded content is sent together before the data.

Even if this processing on the main body side is implemented by software, sufficient efficiency can be obtained.

In the above embodiment, logical operations between line buffers are performed by the CPU 2.
However, simple operations such as exclusive OR can be easily implemented using logic circuits, and efficiency will be further improved if this is done. Furthermore, it is of course possible to perform encoding such as run-length encoding using dedicated hardware instead of the CPU 2.

FIG. 4 is a block diagram showing an embodiment of the output device, where 11 is the main body of the image output device, and 12 is the main body 1 of the input device shown in the first figure.
13 is a CPU, 14 is a ROM 515 in which instructions for controlling the CPU 13 are stored, a RAM 516 is a print control section, and 17 is a printing unit.

As shown in FIG. 2, the RAM 15 has line buffers φ to n that can store multiple lines of image data, but the storage capacity of the RAM 15 may be one page, or 16 to The same principle can be applied to a device having only the width of one printing of about 24 lines.

FIG. 4 shows an example where there is a line buffer (page memory) for one page. As mentioned above, the feature of the image data encoding method handled by this device 11 is that before encoding the data, the exclusive OR with the data before the line is calculated, and the data is run-length encoded. The point is to send it out.

Using this method, the image data is encoded on the input device l side and sent to the device 11.

The process by which this data is restored to its original image by this device 11 and outputted will be explained with reference to the operational flowchart of FIG.

First, in step S21, a command sent from the input device l side is analyzed. In step S22, it is determined whether the command is for the above-mentioned encoded image printing, and if not, the conventional processing is performed in step S23.
Return to 21. If the image data is compressed by the aforementioned encoding, a line counter for the image data is initialized in step S4. The size of the sent image, the period for calculating the exclusive OR, etc. have already been analyzed in step S21 and stored in a predetermined area of the RAM 15.

Next, in step S25, the encoded image data is received, and in step S26, it is developed into a dot image. In step S27, it is determined whether the line is equal to or greater than the line of period number. If the line is less than or equal to period number, the decoded image data is stored as is in line buffer l in step S328.

On the other hand, if the line is the cycle number or higher, step S
In step 29, the exclusive OR of the decoded data and the previous data by a period (line buffer l - period) is taken and stored in line buffer l.

In step S30, the line counter is incremented by 1, and in step S31, it is determined that the image data is finished.

If the process is finished, the process goes to step S21 and waits for the next command; otherwise, the process goes to step S25 to accept the next line of image data. By developing the image in the page buffer in this way, the original image can be restored.

In the above-mentioned embodiment, the encoding operation is performed using the CP in the input device main body.
An example in which the present invention is applied to an input device that is not equipped with a conventionally used encoding function will be described.

FIG. 6 is a block diagram showing another embodiment of the present invention.
is an image input device; 32 is an image encoding device; inside the encoding device 32 is an interface circuit 33; a buffer (RAM) 34 for temporarily storing image data;
, encoding circuit 35, RAM for storing encoded data
36 are provided. Further, 37 is the main body of the computer. 3
Each block from 3 to 36 is assembled on one board 37
It is used by being installed in the expansion slot of the computer main body.

Further, the RAM 36 has a line buffer area LA including line buffers φ to n for a plurality of lines as shown in the second diagram.

Next, an outline of the operation shown in FIG. 6 will be explained.

When an image data input request is issued from the computer main body 37 to the image input device 31 through the interface circuit 32, the image input device 31 reads an image such as an image drawn on paper or a photograph using an image sensor such as a CCD and converts it into a digital data. and sends it to 33 interface circuits. At this time, the input mode (for example, whether it is two gradations, multi-gradation (dither), input resolution, etc.) is also transmitted from the main body 37 to the input device 31 through the interface circuit 32. This input mode is also held in a latch within the interface circuit 33 and is used to determine the period of the line on which the logical operation is performed. For example, for two gradations, use l as the period, and for dither data, use the dither box size as the period.

Next, the image data sent from the input device 31 in response to an input request is output dot by dot by an interface circuit 33 to a line buffer 34 and an encoding circuit 35.The line buffer is composed of elements such as shift registers.
At the same time that one dot of data is output from the interface circuit 33, the corresponding dot data of the previous line by one cycle is output to the one-dot encoding circuit 35. The encoding circuit 35 takes the exclusive OR of the line n data output from the interface circuit 33 and the line n-period data output from the line buffer 4, and calculates the result (φ or l) for each dot. are counted one after another, run-length encoded, and the result is stored in RAM
36. After that, the interface circuit 33
When the main body 37 of the computer is informed that data for a line has been input, the main body 37 can read out the RAM 36 and obtain encoded image data. The main body 37 also connects the interface circuit 3 to input the next line.
3, a request to send one line of image is sent to the input device 31. Naturally, before inputting the first line, all dots in the line buffer r must be cleared to φ.

By decoding the data imported into the main body in this way and similarly calculating the exclusive OR, a completely input image can be restored. Even if this processing on the main body side is implemented by software, sufficient efficiency can be obtained.

In the embodiment shown in FIG. 6, data is received and passed between the main body and the input device by handshaking for each line, but by preparing a RAM 36 of sufficient size,
It is also possible to compress all the data for one page, store it in the RAM 36, and then take it out from the main body 37.

〔effect〕

As explained above, by calculating the exclusive OR of image data with the image data immediately before or several lines before, encoding and transmitting, the number of data to be transmitted can be reduced and the image transmission speed can be improved. It is also possible to improve storage efficiency.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the image input device, Fig. 2 is a diagram showing the memory RAM, Fig. 3 is an operation flowchart of encoding, Fig. 4 is a block diagram of the image output device, and Fig. 5 is a diagram of decoding. FIG. 6 is a diagram showing another embodiment of the present invention, in which 1 is an image input device, 2 is a CPU, and 4 is a RAM. 6 is an input section, and 17 is a printing unit. A1 No. 20 ■Buddha painting

Claims (1)

[Claims] An image data encoding method characterized by encoding an exclusive OR of image data input sequentially for each line and image data immediately preceding or several lines before.