JPS6074875A - Image signal processing method and device - Google Patents

Abstract

PURPOSE:To improve the reliability and also to attain the miniaturization for a picture signal processor by changing a part of the picture information when the compression factor of picture information is less than a fixed level and therefore preventing the deterioration of the compression factor less than the fixed level. CONSTITUTION:The picture information is read by the scan reader 1 of a picture signal processor and applied to an original picture changing device 3 after quantization. The output of the device 3 is applied to a compression coding transmitter 5 and a compression code number estimating device 6 via a line 4. The code number estimated by the devide 6 is applied to a deciding device 12 through a line 11. The device 12 decides the need to give a change to the original picture information. When the compression factor of the picture information is less than a fixed level, the result of decision of the device 12 is applied to the device 3 through a line 10. Then the original picture information is partly changed. This partial change of the original picture information prevents the deterioration less than the fixed level for the original picture information sent from the transmitter 5.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an image signal processing method and apparatus used for transmitting and storing image information.

Conventional configurations and their problems Conventionally, when image information is transmitted or stored, redundancy in the image information is used to improve the information transmission efficiency and reduce the amount of storage media required. (remove) and K
Yes, information is compressed. This compression process is performed in both analog and digital technology fields, but while high compression rates can be obtained in the digital technology field, when looking at a certain compression method, the compression rate varies significantly depending on the image. For example, the compression ratio varies from 1/20 to about 10 times.
9% is a compression ratio within the range of about 1/20 to 1/2. In extremely rare cases, there are cases of 2 to 5 times the size, but there are almost no cases of 10 times the size. In other words, if the compression ratio is 1 or more, the number of codes for compressed image information will be greater than the number of codes when the original image is read and quantized, so the efficiency of code transmission and storage will be reduced. I don't like it. Furthermore, in the circuit that performs the compression process, it is necessary to prepare a device that takes into account the maximum amount of code and a processing time, resulting in extremely poor cost performance. Moreover, there is no guarantee that everything will be okay.

Purpose of the Invention The present invention provides that when the compression rate of image information becomes worse than a certain value,
The present invention provides an image signal processing method and apparatus that can prevent the compression ratio from becoming worse than a certain value by changing a part of image information, thereby making the apparatus more compact and highly reliable. .

Structure of the Invention The present invention compresses and encodes image information and changes the image information that is input to a device that uses the image information so that the number of compression codes for the image information in one certain area does not exceed a certain value. This aims to achieve the above objectives.

The present invention also provides an input means for inputting image information, an estimating means for estimating the number of compression codes from the image information inputted by the input means, and whether a part of the image information should be changed in accordance with the estimate of the estimating means. The above object can be achieved by providing a determining means for determining whether or not the present invention is acceptable, and an image information changing means for changing the image information according to the determination by the determining means.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

The image information is scanned and read, compressed, and transmitted/transmitted.
An example in which the present invention is applied to a restoration/printing system will be described below. Also, without scanning the image information, reading it from the storage device, or transmitting the compressed code,
Various other application combinations exist, such as storage in a storage device, which can be understood from the following description and are within the scope of the application of the present invention.

FIG. 1 shows a block diagram of an image signal processing device according to an embodiment of the present invention.

In FIG. 1, image information is read by a scanning reader 1 and quantized to become an image information code. The image information code is sent to the original image resetting device 3 via line 2. The original image changing device 3 makes a predetermined change to the original image only when it is necessary to change the original image, and prevents the compression ratio from deteriorating by more than a certain value when the original image within a certain area is compressed and encoded. The image information code is then sent via line 4 to a compression encoding/sending device 6 and a compression code number prediction device 6.

Now, the compressed information processed by the compression encoding/sending device 6 is sent to the receiving/restoring device 8 at the receiving point via a communication line 7 provided by the Telecommunications Corporation, etc., where it is restored to image information. . The image information is sent via line 9 to a printing device 10, where it is printed and visualized.

On the other hand, the compression code number prediction device 6 sends the number of codes predicted from the image information code input via the line 4 to the determination device 12 via the line 11, which determines whether or not it is necessary to make changes to the original image. send. The determination signal generated by the determination device 12 is sent to the original image changing device 3 via a line 13. Note that the compression code number prediction device 6 can also use the compression code creation device in the encoding/sending device 5.

The operation of the above configuration will be explained below.

Note that in the case shown in FIG. 2, the original image 200 is composed of pixels 203
It depicts how it is composed of a set of .

Now, the image is scanned and read by the scanning and reading device 1, and information such as brightness and color of the image is converted into electrical signals.

Through scanning, image information is obtained from the image as quantized minute areas (pixels) and brightness values of the minute areas whose brightness is assumed to be constant, but the image information is also quantized. In FIG. 2, the direction of arrow 201 is the main scanning direction, and the direction of arrow 202 is the sub-scanning direction. Also, the number (1.2.3, 4..., m) given at the top of Figure 2 is the pixel number 204, and the number given at the left side of Figure 2 (1°2.3) is the pixel number 204. . . . , n) is the scanning line number 205. The position of the pixel P formed there is P
(pixel number, scanning line number).

For example, the position of the pixel indicated by number 203 in FIG. 2 is P(2,a).

One-dimensional processing is used as a compression method for binary image information.

The method includes the run-length method, and the two-dimensional processing method includes the two-line activation method, the changing point drawing method as seen in modiphite lead, and the adaptive prediction method.

Further, for multivalued images, there are DPCM method, orthogonal transform method, adaptive prediction method, block method, etc. The present invention is not subject to any restrictions, such as whether the image is black and white or color, binary or multivalued, or the number of scanning lines used for processing, such as within one scan (one-dimensional) or multiple scanning lines (multidimensional). , 1) The code of image information is compressed, and 2) the compression rate varies depending on the content of the image. It applies to the case.

A case will be described in detail below, taking as an example a case where a monochrome image is used for multidimensional adaptive prediction using a binary image.

JP-A-56-5'8368 describes a method of predicting pixel values using four scanning lines and encoding the prediction results using a modified Huffman code. As seen in this case, there is a method of obtaining the number of codes from the actual compression device itself or a means for simulating it (hereinafter referred to as the first means of knowing the number of compression codes). Note that the compression rate can be considered to be approximately equal to the number of compression codes in the area under consideration divided by the number of codes of the original pixel. The reason why they are said to be approximately equal is that codes for image properties, error control, things necessary for transmission, etc. are sometimes added to pure compression codes and called compression codes. Furthermore, the above-mentioned shimmy rate means is a simplified method that is basically the same. For example, when simulating an adaptive prediction method using 12 pixels, adaptive prediction is performed using 4 pixels, and the prediction result is This also includes a case where the average value of the prediction result is multiplied by the average value of the number of Huffman codes, and then multiplied by the impending degree, without changing the number of codes using a modified Huffman code.

In the case of the first means described above, the number of compressed codes can be obtained from inside the encoding/sending device 6 and sent to the determination device 12 without newly providing the compression code number predicting device 6 shown in FIG. . The second way to know the number of compression codes is to know the nature of the image and the number of compression codes in association, although the accuracy is rough. As an example, consider a case where the number of compression codes is counted in units of one scanning line.

The number of changes is counted from the beginning of one scanning line of the original image. By multiplying this by a certain number, you can roughly know the number of compression codes at that point. Alternatively, among the change points, only those whose values are different from the previous line are measured, and the number is multiplied by a certain number to find the number of compression codes. These are the second means of knowing the number of compression codes. Information that has a certain association with the number of compression codes described above or the number information approximated thereto is transmitted via all,
It is sent to the determination device 12. What is shown in FIG. 3 is an explanation of adaptive prediction using the four pixels described above. The color of the pixel 301 indicated by ■ is predicted from the color combination of the pixel 302 indicated by R1, R2, R3°R4, and the number of matches/mismatches with the actual color is associated with the number of compression codes. Become. The table shows the color combinations and predicted values for R1-R4. In the table, Q is white and 1 is black.

(L lower needle 6) (〇-white 1-black) Next, the determination device 12 will be explained. A counter is prepared in the determination device 12. Immediately before processing the first pixel in one fixed area for counting compression codes, the value of the counter is set to ○, and as the pixels are processed, the compression code number prediction device 6
Accumulate the number of codes sent from. When this integrated value exceeds a certain value, the determining device 12 sends a determining signal to the original image changing device 3 via the line 13, instructing the original image code to be changed. Examples of one fixed area for counting the above-mentioned compression codes include 1) one line, 2) one of the blocks obtained by dividing one line by a plurality of blocks, and 3) an area of a pixels by b pixels. (However, a and b are integers smaller than m and n).

One constant area counting compression codes is one line (1
The operation of the original image changing device 3 will be described by taking as an example the case where there are two scanning lines j. Furthermore, adaptive prediction using four pixels will be taken as an example.

Process the pixels of the scanning line numbered j starting from pixel number 1,
When receiving the determination signal at the pixel number, the original image changing device 3 changes the pixels after the pixel number (k+1). (However, okl, (k+1)km.) The method of change is to make the number of compression codes 0, almost 0, or significantly less than before the change. be. 1
For example, the pixel number (k+1) and subsequent pixels of the scanning line number i are changed to the pixel number (k11) of the scanning line number N-1).
Replace with the pixel after the pixel. In this way, when a compression method based on adaptive prediction is used, there will be no misprediction for the changed portion, and therefore the number of compression codes can be extremely reduced compared to before the change. In the case of a compression method using one line run length, the number of codes can be significantly reduced by sending the code "same as the previous line" for pixels after pixel (k+1).

Effects of the Invention As described above, the present invention changes a part of the image information when the compression ratio of image information becomes worse than a certain value, thereby preventing the compression ratio from becoming worse than a certain value, thereby reducing the size of the device. Buttons can also be used, and high reliability can be obtained.

In particular, a case in which it is necessary to make changes to the original image is when a black border runs in the scanning line direction on a white background, and the border between white and black is jagged. In such a case, even if a portion of one of the scan lines is replaced by the previous line, it is hardly noticeable visually. Even an office facsimile has a resolution of 8 pixels/mm, and a newspaper facsimile has a resolution of 18 to 36 pixels/mm. According to the present invention, it is possible to prevent the device from requiring a long processing time due to the inconvenience, and to provide a guarantee that the electronic transmission sheet will not become unable to be transmitted in the middle, which has a significant effect.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an image signal processing device according to an embodiment of the present invention, FIG. 2 is a schematic diagram explaining the relationship between pixels of an original image and scanning lines, and FIG. 3 is a diagram explaining a method for predicting pixel values. FIG. 4... Original picture changing device, 6... Compression code number prediction device, 12... Determining device. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
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Claims (2)

[Claims] (1) An image signal that is characterized in that the image information that is input to a device that compresses and encodes the image information is modified so that the number of compression codes for the image information in one certain area does not exceed a certain value. Processing method. (2) an input means for inputting image information; an estimation means for estimating the number of compression codes from the image information input by the input means;
The image forming apparatus includes a determining means for determining whether or not a part of the image information should be changed in accordance with the estimate by the estimating means, and an image information changing means for changing the image information in accordance with the determination by the determining means. Image signal processing device.