JP3340006B2 - Image processing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus provided with an image data storage unit for compressing and storing image data by block coding.

[0002]

2. Description of the Related Art A digital copying machine which handles image data as a digital signal is known as one of image processing apparatuses. FIG. 4 schematically shows the configuration of the digital copying machine of this means. That is, image data is read by the scanner 101, converted into a digital signal by the A / D converter 102, subjected to image processing such as gamma conversion and image quality correction by the image processor 103, and image data is printed on paper by the image output unit 104. Prints an image for each pixel and outputs an image.

In a copying machine that handles an image as a digital signal, the image can be stored in a memory. If the image data can be stored in the memory, the image once captured can be used many times, and the processing and editing such as rotation of the image can be performed by changing the input / output address. However, the amount of information of the image is large, and if it is stored in the memory as it is, a large memory capacity is required (for example, an A4 size document is set to 256 gradations per pixel and the resolution is 400 dp
When read with i, it is about 16 megabytes. ), Since the unit price of the memory is high, the overall cost becomes high. Therefore, a method is generally adopted in which image data is not stored as it is, but is encoded once, the data amount is compressed, and the data amount is stored in a memory. That is, the data can be compressed and stored in the memory, and the required memory amount is reduced to reduce the cost.

In a block coding method in which image data is a compression method, an image is decomposed into blocks as shown in FIG. 5, and a 1-byte density value Lij in the block is averaged by an algorithm shown in FIG. Byte), gradation width index Ld
(1 byte), code φij for each pixel (2 bits x 16)
Data compression. With this encoding method, as shown in FIG. 7, the data amount of 16 bytes of a 4 × 4 pixel block of 1 byte of pixels becomes 6 bytes, and the data amount can be compressed to ／. Qj in FIG. 6 is a representative quantization value at the time of decoding, and is a density value assigned when each code is combined as shown in FIG.

[0005] In recent digital copiers, when red is included in image data, there is a digital copier that can determine a red pixel and output red. For example, as shown in FIG. 9, when a copy of a document in which the area 11 is red and the other area 12 is black is made, red is output as a copy of the document as it is. In such a copy, if the data of the red image is handled as multi-valued data as in the case of the black image, the amount of information increases, so that the red image is generally handled as binary data.

FIG. 10 shows the configuration of a copying machine in which a copying machine capable of outputting two colors has a function of compressing and storing images in the memory. In this configuration, first, in the scanner 21, R, G, and B line sensors are used to read image data of R, G, and B signals for each pixel, and an A / D converter 22.
To convert the signal into an 8-bit digital signal, and the image processing unit 23 performs image processing such as gamma conversion. Here, the red image signal determination unit 24 calculates a difference between the R signal and the G signal for each pixel, and when the difference is larger than a threshold, sets the bit of the red image signal to 1 and converts the G signal to 0. In other cases, the bit of the red image signal is 0 and the value of the G signal does not change. Thereafter, the G signal becomes the density value of the black image. The signal switching unit 26 is connected to B and sends data to the image output unit 27. The image output unit 27 receives these data and outputs an image containing red and black colors.

In the case where image data is compressed and stored in the image storage unit 25 and decoded to output an image, the scanner 2
1. The A / D converter 22, the image processor 23, and the red image signal determiner 24 are the same as the above-described processes when the image storage 25 is not used. In the data from the image processing unit 23 and the red image signal determination unit 24, the density value of the black image is encoded by the above-described block encoding method, and the red image signal is stored as binary. As a result, as shown in FIG. 11, the data for one block is obtained by adding 16 bits (2 bytes) of the red image signal of 16 pixels in the block to the code of the block coding. When output from the image storage unit 25, the black signal is data obtained by decoding a block coding code, the red image signal is output as a binary signal,
The signal switching unit 26 is connected to A and sends data to the image output unit 27. The image output unit 27 receives these data and outputs an image containing red and black colors.

[0008]

However, when such a method is adopted, it is necessary to increase the amount of memory for the red image signal as described above, and if the amount of memory is increased, the cost naturally increases.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide an image processing apparatus capable of outputting a red image signal with the same memory amount as an image processing apparatus that does not output a red image signal. To provide.

[0010]

In order to achieve the above object, a first means is a data generation means for generating binary color pixel data and black multi-tone pixel data from color multi-tone image data. A data decomposer for decomposing each of the binary color pixel data and the black multi-tone pixel data into a predetermined number to generate block data; and a black multi-tone pixel data decomposed by the data decomposer. Density calculating means for calculating the density data of the block data; data coding means for coding the density data calculated by the density calculating means into compressed data comprising a code for each pixel, average data, and a gradation width index; When a pixel value is 1 in a block of binary color pixel data generated by the data generation unit corresponding to the block encoded by the encoding unit, the average generated by the data encoding unit is Characterized in that it comprises a sign change means for converting over data and tone width index to show only the presence position of the color pixel data of two values in the block.

The second means is a data decoding means for decoding compressed data comprising a code for each pixel, average data and a tone width index into density data, and a color decoding means wherein the average data and the tone width index are binary. In the case of a specific value set indicating that pixel data is included, binary color pixel data is arranged in a block based on the position where the binary color pixel data indicated by the code of each pixel exists, and Density of black multi-tone data is 0
And a decryption data changing means for setting the decryption data.

The third means is characterized in that the first means is further provided with a second means.

The fourth means generates binary color pixel data and black multi-tone pixel data from the color multi-tone image data, and generates the binary color pixel data and black multi-tone pixel data. Each data is decomposed into a predetermined number to generate block data, the data decomposing means calculates the density data of the block data of the black multi-tone pixel data decomposed, and the density data calculated by the density calculating means is used for each pixel. In the block of binary color pixel data generated by the data generation unit corresponding to the block coded by the data coding unit, When the value of is 1, the average data and the gradation width index generated by the data encoding means are converted so as to indicate only positions where binary color pixel data exists in this block.

The fifth means decodes compressed data comprising a code, average data, and a gradation width index for each pixel into density data, and the average data and the gradation width index include binary pixel data. In the case of a set of specific values shown, binary color pixel data is arranged in a block based on the position where the binary color pixel data indicated by the code of each pixel exists, and black multi-tone data in the block is placed. Is set to 0.

The sixth means executes the fifth means following the fourth means.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

Since the configuration in this embodiment is the same as the configuration shown in FIG. 10, the same reference numerals are given to the same portions as those in the above-described conventional example in the following description, and the repeated description will be omitted as appropriate. I do.

A feature of the present invention lies in the internal configuration of the image storage unit 25 in FIG. 10, and details thereof are shown in FIG. FIG.
In the black image density value, the data of four lines is stored once in the 4-line FIFO 1 and then coded by the coding unit 2 for each 4 × 4 pixel block, and the data of La, Ld and φij are stored in the memory 4. Is stored. On the other hand, the red image signal is 2
After the signals for four lines are stored in the value 4-line FIFO 3, the signals are input to the encoding unit 2 for each 4 × 4 pixel block. Here, when the value of the block of the density value of the black image being processed by the encoding unit 2 is (a) in FIG. 2, the encoding value is (b) in FIG. At this time, when a red image signal (1) exists in the block at the same position as shown in FIG. 2C, La = 0, Ld = 255 (in the block coding algorithm, the combination of La and Ld is used). ) Is converted to 00 corresponding to 0 of the red image signal block and to 11 corresponding to 1. The data of La, Ld, and φij thus converted are stored in the memory 4. When decoding an image, La, Ld, φ
The data of ij is read out, La and Ld are checked by the decoding unit 5, and if La = 0 and Ld = 255, the block is recognized as a red image signal, and as shown in FIG. 2 (d), the signal corresponding to 00 becomes 0, and the signal corresponding to 11 becomes 1 as shown in FIG.

For other combinations of La and Ld, the density value of the black image is decoded by ordinary block coding, and the red image signal becomes 0 at that time. The density value of the black image and the pixel block of the red image decoded by the decoding unit 5 in this manner are obtained by storing the density value of the black image in the 4-line FIFO 6 and storing the red image signal in the binary 4-line FIFO 7 for red data. Are output from the image output unit for each line. As described above, a block in which a red image exists is indicated by a set of La and Ld that is not generated by normal block coding to indicate that the block is a red image signal, so that the memory for the red image signal is not increased, A digital copying machine that handles a red image and a black image and has an image storage unit that stores compressed image data can be configured.

[0020]

As described above, according to the present invention, the following effects can be obtained.

According to the first aspect of the present invention, data encoding means for encoding the density data calculated by the density calculating means into compressed data comprising a code for each pixel, average data, and a gradation width index; When the pixel value is 1 in the block of binary color pixel data generated by the data generating means corresponding to the block encoded by the means, the average data and the gradation width index generated by the data encoding means Is provided so as to indicate only the position where the binary color pixel data exists in this block, so that the compressed data of the black multi-tone data and the binary color pixel data are separated from each other. It is not necessary to store or transmit the compressed data, and the size of the memory for storing the compressed data and the transmission time of the compressed data can be reduced without increasing the total data amount.

According to the second aspect of the present invention, there is provided a data decoding means for decoding compressed data comprising a code, average data, and a gradation width index for each pixel into density data; In the case of a specific value set indicating that color pixel data of a value is included, binary color pixel data is arranged in a block based on the position where the binary color pixel data indicated by the code of each pixel exists, Since there is provided decoded data changing means for setting the density of the black multi-tone data in the block to 0, the size of the memory for storing the compressed data can be reduced without increasing the total data amount. Transmission time can be shortened.

According to the third aspect of the present invention, since the second aspect of the present invention is further applied to the first aspect of the present invention, the total data amount does not increase.
The memory for storing the compressed data can be reduced in size, and the transmission time of the compressed data can be reduced.

According to the fourth aspect of the present invention, the density data calculated by the density calculating means is encoded into compressed data comprising a code for each pixel, average data, and a gradation width index, and corresponds to the encoded block. When the pixel value is 1 in the block of color pixel data, the average data and the gradation width index generated by the data encoding unit are set so as to indicate only the position where binary color pixel data exists in this block. To convert,
It is possible to reduce the size of the memory for storing the compressed data and shorten the transmission time of the compressed data without increasing the entire data amount.

According to the fifth aspect of the present invention, the compressed data comprising the code, the average data, and the gradation width index for each pixel is decoded into density data, and the average pixel data and the gradation width index are converted to binary pixel data. For a specific set of values that indicate
Since the binary color pixel data is arranged in the block based on the position where the binary color pixel data indicated by the code of each pixel exists, and the density of the black multi-tone data in the block is set to 0, It is possible to reduce the size of the memory for storing the compressed data and shorten the transmission time of the compressed data without increasing the entire data amount.

According to the invention set forth in claim 6, since the invention described in claim 5 is further applied to the invention set forth in claim 4,
It is possible to reduce the size of the memory for storing the compressed data and shorten the transmission time of the compressed data without increasing the entire data amount.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an internal configuration of an image storage unit according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram illustrating processing in an encoding unit in FIG. 1;

FIG. 3 is an explanatory diagram illustrating processing in a decoding unit in FIG. 1;

FIG. 4 is a block diagram illustrating a schematic configuration of a digital copying machine according to an embodiment and a conventional example.

FIG. 5 is an explanatory diagram showing an image data compression system of a block encoding system.

FIG. 6 is an explanatory diagram showing an algorithm of an image data compression system of a block encoding system.

FIG. 7 is an explanatory diagram showing a state when image data is compressed by a block coding method.

FIG. 8 is an explanatory diagram showing density values at the time of decoding.

FIG. 9 is a diagram illustrating a document having red and black images.

FIG. 10 is a block diagram showing a schematic configuration of a copying machine capable of outputting two colors having a function of compressing and storing an image in a memory.

FIG. 11 is an explanatory diagram showing image data for one block.

[Explanation of symbols]

 1, 6 4-line FIFO 2 coding unit 3, 7 binary 4-line FIFO for red data 4 memory 5 decoding unit 21 scanner 22 A / D conversion unit 23 image processing unit 24 red image signal determination unit 25 image storage unit 26 signal Switching unit 27 Image output unit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04N 1/41-1/419

Claims (6)

(57) [Claims] 1. An image processing apparatus for compressing image data by block coding, comprising: a data generating means for generating binary color pixel data and black multi-tone pixel data from color multi-tone image data; Data decomposing means for decomposing each of the value color pixel data and black multi-tone pixel data into a predetermined number to generate block data; and Density calculating means for calculating density data; data coding means for coding the density data calculated by the density calculating means into compressed data comprising a code for each pixel, average data, and a gradation width index; and the data coding means. When the pixel value is 1 in the block of binary color pixel data generated by the data generation unit corresponding to the block encoded by The image processing apparatus characterized by comprising a code changing means for converting average data and tone width index was made to show only the present position of the color pixel data of two values in the block. 2. An image processing apparatus for compressing image data by block coding, comprising: data decoding means for decoding compressed data comprising a code for each pixel, average data, and a gradation width index into density data; When the data and the gradation width index are a specific set of values indicating that binary color pixel data is included, the binary value of the binary color pixel data in the block is determined based on the position where the binary color pixel data indicated by the code of each pixel exists. An image processing apparatus, comprising: decoded data changing means for arranging color pixel data and setting the density of black multi-tone data in a block to 0. 3. An image processing apparatus for compressing image data by block encoding, comprising: data decoding means for decoding compressed data comprising a code for each pixel, average data, and a gradation width index into density data; When the data and the gradation width index are a specific set of values indicating that binary color pixel data is included, the binary value of the binary color pixel data in the block is determined based on the position where the binary color pixel data indicated by the code of each pixel exists. 2. The image processing apparatus according to claim 1, further comprising: decoded data changing means for arranging color pixel data and setting the density of black multi-tone data in the block to 0. 4. An image processing method for compressing image data by block encoding and performing image processing, wherein binary color pixel data and black multi-tone pixel data are generated from the color multi-tone image data. The value color pixel data and black multi-tone pixel data are decomposed into a predetermined number to generate block data, and the data decomposer calculates the density data of the decomposed black multi-tone pixel data block data. The density data calculated by the density calculation means is encoded into compressed data including a code, an average data, and a tone width index for each pixel, and the data generation means corresponding to the block encoded by the data encoding means. When the pixel value in the generated block of binary color pixel data is 1, the average data and the gradation width index generated by the data encoding means are added to the binary color pixel data block. The image processing method that is characterized in that conversion to show only the positions in the presence of over data. 5. An image processing method for compressing image data by block encoding and performing image processing, wherein compressed data composed of a code for each pixel, average data, and a gradation width index is decoded into density data, When the gradation width index is a specific value set indicating that binary color pixel data is included, the binary color pixel is included in the block based on the position where the binary color pixel data indicated by the code of each pixel exists. An image processing method, comprising arranging data and setting the density of black multi-tone data in a block to zero. 6. An image processing method for compressing image data by block coding and performing image processing, wherein binary color pixel data and black multi-tone pixel data are generated from the color multi-tone image data. The value color pixel data and black multi-tone pixel data are decomposed into a predetermined number to generate block data, and the data decomposer calculates the density data of the decomposed black multi-tone pixel data block data. Then, the density data calculated by the density calculation means is encoded into compressed data including a code for each pixel, average data, and a gradation width index, and the data generation means corresponding to the block encoded by the data encoding means. When the pixel value in the generated block of binary color pixel data is 1, the average data and the gradation width index generated by the data encoding means are added to the binary color pixel data block. The data is converted so as to indicate only the position where the data exists, and the compressed data composed of the code, the average data, and the gradation width index for each pixel is decoded into the density data, and the average data and the gradation width index are binary color pixels. In the case of a specific value set indicating that data is included, the binary color pixel data is arranged in the block based on the position where the binary color pixel data indicated by the code of each pixel exists, and the black Setting the density of the multi-tone data to 0.