JPH04151976A - Picture processing unit - Google Patents

Abstract

PURPOSE:To easily reproduce a picture with high quality by processing a picture resulting from bringing other areas than a white/black binary picture area of an input picture into a white level and a picture resulting from bringing areas other than multi-value or color binary picture areas into a white area so as to reduce a data quantity without deteriorating picture quality. CONSTITUTION:A picture scanner 1 reads a picture and stores the result to a picture memory 2 as a multi-value data. An image separation section 3 reads a data of an input picture from the memory 2 to separate a binary picture area and a multi-value picture area and writes the result of separation into a memory 4. A processing section 5 reads a multi-value data of the input picture from the memory 2 and reads separation result information from the memory 4, applies unsharpening processing and binarizing and writes the result to a memory 6. Picture elements other than the binarizing area are set to 0 data. A conversion section 7 reads a multi-value data and result information from the memories 2, 4, applies smoothing processing and compresses line density and data and the processed multi-value data is written in a memory 8. A compression/expansion section 2 compresses the data and send it externally by a transmission section 13.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an image processing device such as an image file device, a still image transmission device, and an electronic copier that process image data such as documents read by an image scanner. .

[Prior art] Binary images such as characters have a high resolution (for example, 4.OOdpi
), it is preferable from the viewpoint of image quality to perform sharpening and binarization processing, but for multivalued images such as photographs, it is desirable to have higher gradations even if the resolution is somewhat low (for example, 200d
pi, 256 gradations).

In terms of data volume, a binary image can represent one pixel with one bit, but a multi-valued image uses 8 bits to represent each pixel (in the case of 256 gradations), and color 3
24 pits are required.

Furthermore, when compressing image data, the optimal data compression method is different for binary images and multivalued images.

” From the perspective of two series, it is essentially unreasonable to process the entire image containing a mixture of binary and multivalued areas with a uniform resolution and number of gradations. should be distinguished and treated appropriately.

Various methods have been proposed for performing such processing for each image area. An example is shown below.

Prior art 1 A binary image area and a halftone image area are identified from the image signal obtained by the image reading means, and a high-resolution binarized image signal is output for the binary image area, and a dithered image signal is output for the halftone image area. A low-resolution image signal subjected to low-resolution processing and averaging processing is output (Japanese Patent Application Laid-open No. 132571/1983).

Prior Art 2 For an image input as multivalued data, it is determined whether it is halftone or binary in units of predetermined blocks. Halftone blocks are converted to a single pixel with the average density within the block, and binary blocks are converted to a bit pattern that corresponds to the density pattern within the block, thereby compressing the amount of data and storing or transmitting it. (Unexamined Japanese Patent Publication 1986-
No. 191475).

Prior art 3 A photographic area is extracted as a rectangle from a human image, the photographic area of the input document is replaced with black pixels line by line, and then binarized, and the data is converted into data using a method suitable for binary images such as MR encoding. On the other hand, the photographic area is formatted and then data compressed using a method suitable for multivalued images such as vector quantization or transform encoding, and the two types of compressed data obtained in this way are stored. , or transmit. When reproducing an image, the compressed data of the photo area and the other compressed data are decoded using methods suitable for each and combined (Japanese Unexamined Patent Publication No. 144778).

Conventional technology 4 Original image data inputted by a multilevel scanner is
Convert value data to multi-value data with a lower number of gradations, or convert to pseudo-halftone data using the dither method, and select binary data in the binary image area of the document according to pre-specified image area position information. Select and output multi-valued data or pseudo-halftone data in the halftone area of the original (
JP-A-63-59264, JP-A-63-142964
issue).

[Problems to be Solved by the Invention] In any of the above conventional techniques, each binary image region and each multivalued image region in an input image are treated and processed as if they were independent images, so the position of each image region is It is necessary to store the information and control the compositing position of the data of each image area according to the position information of each image area when compositing images to reproduce the input image, which increases the complexity of the processing system and increases the image quality. Image distortion tends to occur at area boundaries. In particular, in conventional technology 3, when processing a variety of images, it is not easy to perform rectangular extraction and shaping of a multivalued image area with high precision through automatic processing.
Not only does the processing time tend to increase, but there is a risk that the quality of the reproduced image will deteriorate significantly due to a slight processing error. Furthermore, since prior art I requires specifying an image area in advance, it cannot be applied to applications that process arbitrary images.

The object of the present invention is to provide an image file device, a still image transmission device,
In image processing devices such as electronic copiers, it is possible to reduce the amount of data without deteriorating the image quality and without complicating the processing system for arbitrary black and white or color images containing a mixture of binary and multivalued image areas. The aim is to reproduce images in high quality.

[Means to solve the problem]

The invention described in claim (1) of the claims provides an image area separating means for separating a binary image area and a multivalued image area of an input image given as multivalued data, and an image area separation method using the image area separation means. According to the result, a binarization processing means for obtaining a processed image in which the human image is subjected to sharpening processing and binarization processing in which areas other than the binary image area are white; The invention as set forth in claim (2) of the claims is characterized in that it comprises a linear density conversion means for obtaining a processed image that has been rendered white and has undergone linear density conversion processing to lower the resolution. an image area separation means that separates a binary image area and a multivalued image area of an input image given as , and further separates the binary image area into a color area and a monochrome area, according to the image area separation result by the image area separation means, 2 black and white images for the input image.
A binarization processing means for obtaining a processed image that has been subjected to sharpening processing and binarization processing in which areas other than the value image area are white, and a multivalue image area and a color binary image area are removed from the input image. The invention as set forth in claim (3) of the claims is characterized in that it comprises a linear density converting means for obtaining a processed image that has been subjected to linear density converting processing to lower the resolution, with the area being white. In the invention as set forth in claim (1) or (2), the binary compression means and linear density conversion means obtain a processed image by subjecting the processed image by the binarization processing means to data compression using a compression method for binary images. The invention as set forth in claim (4) of the claims is characterized in that it comprises a multi-value compression recess that obtains a processed image by subjecting the processed image to data compression using a multi-value image compression method. In the invention described in item (3), a binary decompression means expands a data-compressed image by a binary compression means into an image before data compression, and a multi-value decompression means expands a data-compressed image by a multi-value decompression means into an image before data compression. a decompression means, a linear density inverse conversion means for performing linear density conversion inverse to the linear density conversion by the linear density conversion means on the image decompressed by the multi-value decompression means, data of the image processed by the linear density inversion means; The invention as set forth in claim (5) is characterized in that it comprises means for synthesizing the data of the decompressed image by the value decompression means. Data is output in monochrome black for pixels in the black and white binary image area,
Pixels in other areas are characterized by having means for outputting in a plurality of colors.

[For production]

According to the invention described in claims (1) to (4), each image area of the input image is not divided and handled as if it were an independent image, but the input image is an image in which areas other than the black and white binary image area are white. In order to process the image as an image in which areas other than the multilevel or color binary image area are white, images corresponding to each image area are simply superimposed and synthesized without using the position information of each image area. Image restoration is possible, the processing system for image restoration is simple, and image distortion does not occur at the boundaries of image areas.

According to the invention described in claim (1) or (2), a black and white binary image area where resolution is important is sharpened and binarized,
Multilevel image areas or color where gradation is more important than resolution
Since the resolution of binary image areas is lowered by linear density conversion, binary image areas such as black characters can be output in binary at high resolution while reducing the amount of data, and multi-value areas such as photographs and color characters can be output in high resolution. It is possible to output a color binary image area in high gradation multi-value.

According to the invention set forth in claim (3), the image processed by the binarization processing means is processed using a data compression method suitable for binary images.
The images processed by the linear density conversion means are each compressed using a data compression method suitable for multivalued images. In addition, the data compression efficiency of white areas is good in all processed images.

Therefore, a high overall data compression rate can be obtained without deteriorating image quality.

According to the invention set forth in claim (5), black characters, black lines, etc. can be reproduced with high quality using a single black color, and at the same time, a portion of color such as colored characters can be reproduced in high-gradation color.

〔Example〕

Fig. 1 is a block diagram showing the outline of the functional configuration of the first embodiment of the present invention using a bus structure, Fig. 2 is a schematic flowchart showing the flow of processing at the time of image input in this embodiment, and Fig. 3 is this embodiment. 3 is a schematic flowchart showing the flow of processing when the image amount is rough.

In FIG. 1, 1 is a high-resolution, high-gradation monochrome multivalued image scanner for reading images; 2 is an input/output image memory for storing input image data or output image data;
3 is an image area separation unit that separates the binary image area and multivalued image area (image area separation) of the input image based on the multivalued data of the input image; 4 is the separation unit in which information on the image area separation result is written. This is the result memory.

5 is a binarization processing unit that performs sharpening and binarization processing on multivalued image data according to the image area separation results, 6 is a binary image memo 1 that stores binary digital image data, and 1 huff is the image area separation result. 8 is a multi-value image memory that stores multi-value digital image data.

9 is a binary compression/expansion unit that performs data compression processing or expansion processing (including level conversion) of binary digital image data;
Reference numeral 10 denotes a multi-value compression/expansion unit that performs data compression processing or expansion processing of multi-value digital image data.

11 is a multi-value output printer that outputs multi-value digital image data; 12 is an optical disk device that stores digital image data; and a transmission section that transmits or receives compressed image data.

Furthermore, there is a control section for controlling the entire device and an operation section for the user to input commands, etc., but these are not shown.

Next, a description will be given of processing when an image is input, data is compressed, and stored or sent regularly.

An image is read with high resolution and high gradation by an image scanner 1, and is stored in an input/output image memory 2 as multivalued data.

(Step 1.00 in Figure 2).

The image area separation unit 3 reads input image data from the input/output image memory 2, separates the input image into a binary image area and a multivalued image area, and uses, for example, the binary image area as information on the image area separation result. 1 is written in the separation result memory 4 in association with the pixel of the O1 multivalued image area (steps 1-2 in FIG. 2).

In this embodiment, in this image area separation, the character portion and the white background portion of the adjacent pixel are made into a binary image region, and the photograph portion and the halftone dot portion are made into a multivalued image region. Such image area separation is possible in various ways, but for example, the method proposed by the same applicant in 1999
The method described in detail in the specification and drawings of the '3242 patent application may be used. Further, image area separation may be performed in either a pixel-by-pixel manner or a block of multiple pixels as a unit; however, in this case, image area separation is performed in pixel-by-pixel units.

The binarization processing unit 5 reads the multi-value data of the input image from the input/output image memory 2, simultaneously reads the image area separation result information from the separation result memory 4, and sharpens the multi-value data of the input image (strong edges! II) After performing the processing, perform binarization processing using a specific threshold value and write the processing result data to the binary image memory 6, but pixels with image area separation result information of 1, that is, pixels outside the binary image area is forcibly set to white (0) data (step 104 in FIG. 2).

The linear density conversion/inverse conversion section 7 acts as a linear density conversion section,
Multi-value data and image area separation result information of the input image are read from the input/output image memory 2 and the separation result memory 4, respectively, and the multi-value data of the input image is subjected to smoothing processing to prevent the occurrence of moiré, and this processing result data is After forcibly converting the pixels whose image area separation result information is O to white (0), linear density conversion processing lowers the resolution. The linear density is reduced to 1/2, the image data is compressed to 1/4, and the multi-value data resulting from the processing is written into the multi-value image memory 8 (step 106 in FIG. 2).

In this way, high-resolution binary image data is obtained in the binary image memory 6, and high-gradation multi-value image data with a slightly lower resolution is obtained in the multi-value image memory 8.

Both the binary compression/expansion unit 9 and the multilevel compression/expansion unit 10 act as compression units, and compress the binary data in the binary image memory 6 using the compression method for binary images. 108), the multi-value data in the multi-value colorimetric memory 8 is compressed using a multi-value image compression method (step 110).

Each compressed data is recorded on an optical disc according to a predetermined format by the optical disc device 12, or transmitted to the outside by the transmission unit 13 (step 12 in FIG. 2).

As the data compression power in the binary compression/expansion section 9, for example, the Modified Huffman (MH) Itq encoding method, which is standardly used in facsimile, is used. As a data compression method in the multilevel compression/expansion unit 10, for example, the ADCT method (Adaptive Discrete Co51ne), which is a standard method for still image compression, is used.
Transform: adaptive discrete cosine transform method) is used, and compression is performed using standard 8/8 pixels (16X] 6 pixels before linear density conversion) as one block.

Next, processing for reproducing compressed image data will be described.

The compressed binary data and multi-value data from the optical disk device 12 or the transmission section 13 are input to the binary compression/expansion section 9 and the multi-value compression/expansion section 10, respectively (steps 200 and 202 in FIG. 3). .

The binary compression/expansion section 9 acts as an expansion section, expands the input binary data into uncompressed binary image data, and writes it into the binary image memory 6 (step 204 in FIG. 3). The multi-value compression/expansion unit IO similarly acts as an expansion unit, expands the input multi-value data into uncompressed multi-value image data, and writes it into the multi-value image memory 8 (step 206 in FIG. 3).
).

The linear density conversion/inverse conversion unit 7 acts as a linear density inversion unit, reads multivalue data from the multivalue image memory 8, performs a conversion (enlargement) inverse to linear density conversion, and then transfers it to the input/output image memory. 2 (step 208 in FIG. 3). In this embodiment, since the image is reduced to 1/2 by linear density conversion, the image is enlarged to 2 times by interpolating pixels using, for example, the average density of adjacent images in the inverse conversion.

After that, the binary compression/expansion unit 9 (or control unit)
The binary data is read from the value image memory 6, and only the black pixel data (1) is converted into a multi-value level value (for example, if the number of bits of the multi-value data is 8 bits, 256 levels from O for white to 255 for black) 256) and write it to the input/output image memory 2, the reproduced image is synthesized on the input/output image memory 2 (step 210 in FIG. 3).
).

By outputting the multi-value data obtained in the input/output image memory 2 in this way by the multi-value output printer 11,
A hard copy of the reproduced image is obtained (step 2I2 in FIG. 3).

As is clear from the description of this embodiment, according to the present invention,
Separate the image areas of images that contain a mixture of halftone areas such as photographs and binary image areas such as text, and efficiently compress data by applying the optimal resolution and compression method to each image area. Therefore, it is possible to construct a filing device, a stationary transmission device, an electronic copier, etc., which can efficiently store or transmit a large amount of document images, etc.

FIG. 4 is a block diagram showing the outline of the functional configuration of the second embodiment of the present invention using a bus structure, FIG. 5 is a schematic flowchart showing the flow of processing at the time of image input in this embodiment, and FIG. 6 is this embodiment 3 is a schematic flowchart showing the flow of processing when outputting an image in FIG.

With reference to FIG. 4, the differences between the configuration of this embodiment and the configuration of the first embodiment will be explained. In this embodiment, a color multivalued image scanner la is used to process color images. In addition, the image area separation unit 3a separates a color area and a black and white area in addition to separating a binary image area and a multivalued image area similar to the image area separation unit 3 of the first embodiment. The input image is separated into a black and white binary image area and a multivalued or color binary image area. Further, the difference between the binarization processing unit 5a and the binarization processing unit 5 of the first embodiment is R and G.

Two points are that B data is handled, and that color pixels are forcibly made white even in a binary area. In addition, the printer can print Y (yellow), M (magenta), C (cyan), Bk (black).
A color multi-value output printer lla that is capable of color multi-value recording using printing is used. Furthermore, in this embodiment, the color image data input from the color multivalued image scanner 1a is expressed as R (red), G (green), and B (blue) color data, and is processed as is.''-1 output Y, M, C for outputting image data to a printer.

A color processing unit 14 is added to process a signal corresponding to the amount of Bk ink.

Next, a description will be given of processing when an image is input, data is compressed, and stored or transmitted.

Scanner A reads an image at high resolution and high gradation, and stores it in the input/output image memory 2 as multivalued data (for example, 400 dpj, 8 bits each for R2O and B) (step 300 in FIG. 5).

The image area separation unit 3a reads input image data from the input/output image memory 2, separates the input image into a monochrome binary image area and a multivalued image area/color binary image area, and performs image area separation. As result information, for example, 0 is written in association with the pixels in the monochrome binary image area, and 1 is written in association with the pixels in the multivalued/color binary image area, respectively, in the separation result memory 4 (
Step 302 in FIG. 5).

In this image area separation, as in the first embodiment, image area separation into a binary image area and a multivalued image area and determination between a color area and a black and white area are performed. This color/black and white area determination is
For example, find the difference between two colors among R, G, and B, and select the pixel for which the maximum difference exceeds a certain threshold as a pixel in the color area.
This can be done by making other pixels into black and white area pixels. Further, this determination can be made in units of one pixel or in units of blocks of nXn pixels, but here, it is assumed to be in units of one pixel. Through such image area separation, for example, the character part of a black character and the white background part of the adjacent pixel become a monochrome binary image area, the photograph part and the halftone part become a multivalued image area, and the color character part and its adjacent white background part become a color binary image area. This becomes the image area.

The binarization processing unit 5a reads the multi-valued data of each color of 170 and B of the input image from the input/output image memory 2, and simultaneously reads the image area separation result information from the separation result memory 4.
Maximum single color data among G, B data or R, G, B
The brightness data calculated from the data is subjected to sharpening (edge emphasis) processing, then binarization processing using a specific threshold value, and the processing result data is written to the binary image memory 6, but the image area Pixels whose separation result information is 1, that is, pixels outside the monochrome binary image area, are forcibly set to white (0) data (step 304 in FIG. 5).

The linear density conversion/inverse conversion section 7 acts as a linear density conversion section,
Multi-value data and image area result information for each color of R, G, and B of the input image are read from the input/output image memory 2 and the separation result memory 4, and the multi-value data of the input image is processed for each color of R, G, and B. As in the first embodiment, smoothing processing, processing for forcibly converting pixels whose image area separation result information is O to white (0), and linear density conversion processing to lower resolution are performed, and the R, G of the processing result is , B are written into the multivalued image memory 8 (step 306 in FIG. 5).

In this way, high-resolution binary image data is obtained in the binary image memory 6, and multi-value image data for each color of R2O and B with a slightly lower resolution and high gradation is obtained in the multi-value image memory 8.

Both the binary compression/expansion unit 9 and the multilevel compression/expansion unit 10 act as compression units, and compress the binary data in the binary image memory 6 using the compression method for binary images. 308), R, G, B in the multivalued image memory 8
The multi-value data of each color is compressed using a multi-value image compression method (step 310). This data compression method may be the same as that of the first embodiment. Each compressed data is recorded on an optical disc according to a predetermined format by the optical disc device 12, or transmitted to the outside by the transmission unit 13 (step 312 in FIG. 5).

Next, processing for reproducing compressed image data will be described.

The compressed binary data and multi-value data from the optical disk device 12 or the transmission section 13 are input to the binary compression/expansion section 9 and the multi-value compression/expansion section 1o, respectively (steps 400 and 402 in FIG. 6). .

The binary compression/expansion section 9 acts as an expansion section, and expands the input binary data into uncompressed binary image data and writes it into the binary image memory 9 (step 404 in FIG. 6). The multi-value compression/expansion unit 10 similarly acts as an expansion unit, and expands the input multi-value data of each color of R, G, and B into multi-value image data before compression, and writes it into the multi-value image memory 8 (the Step 406 in Figure 6).

The linear density conversion/inverse conversion unit 7 acts as a linear density inversion unit, reads multivalue data of each color of R, G, and B from the multivalue image memory 8, and performs a conversion (enlargement) inverse to linear density conversion on this data. After that, it is written into the input/output image memory 2 (step /1.08, 410 in FIG. 6).

Next, read the binary data and the multi-value data of each color of R, G, and B obtained in the input/output image memory 2 in [color processing section] 4, and for pixels whose binary data is black (1), a single black color is used. B for records
Output k data (Y, M, C color ink amount is zero),
On the other hand, for white (0) pixels of binary data, R, G
, B color data is converted into Y, M, and C color ink amounts using a certain calculation formula, and the so-called undercolor removal process (
Y, M, C for recording by UCR processing).

Data on the amount of ink for each color of Bk is output (step 412 in FIG. 6).

The color multi-level output coupler l□ 11a receives and records the data of the ink amounts of each color of Y, M, C, and Bk obtained by the color processing via the input/output image memory 2 or directly. Record it on paper (step 414 in FIG. 6).

Note that the R, G, and B data of the image are input to Y at the input stage.

It may also be converted into M and C data. In this case, the color/black and white determination in the image area separation unit 3a is Y, for example.

The maximum value of the difference between the M and C color data may be compared with the threshold value. Further, in the binarization processing section 5, Y and M are stored.

Sharpening and binarization may be performed on the largest portion of the C data.

As is clear from the description of this embodiment, according to the present invention,
Efficiently separate black-and-white images or color images that contain a mixture of halftone areas such as photographs and binary image areas such as text, and apply the optimal resolution and compression method to each image area. It is possible to construct fine ring devices, still image transmission devices, and electronic copiers that can compress data and efficiently store or transmit large amounts of document images, etc., and can output black characters in a single black color, resulting in extremely high-quality characters. can be reproduced.

〔Effect of the invention〕

According to the invention described in claim (1) or (2), black-and-white or color images containing a mixture of halftone areas such as photographs and binary areas such as characters can be processed with the optimal resolution and number of gradations for each image area. By applying it, you can efficiently express high image quality with a small amount of data,
In addition, composition during image restoration can be performed simply, complicating the processing system can be avoided, and image distortion can be prevented from occurring at the boundary of the image area. According to the invention set forth in claim 4), efficient data compression and high-quality reproduction of black and white or color images in which halftone areas such as photographs and binary areas such as characters are mixed are possible. According to the invention described in ), black characters, black line figures, etc. can be reproduced with high quality using a single black color, and at the same time, a portion of color such as colored characters can be reproduced in color with high gradation.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an outline of the functional configuration of the first embodiment of the present invention using a bus structure, and FIG. 2 is a schematic flowchart 1 showing the flow of processing during image input in the first embodiment of the present invention. , FIG. 3 is a schematic flowchart showing the flow of processing at the time of image output in the first embodiment of the present invention, FIG. 4 is a block diagram showing the outline of the functional configuration of the second embodiment of the invention using a bus structure, and FIG. The figure is a schematic flowchart showing the flow of processing when an image is output manually in the second embodiment of the present invention, and FIG. 6 is a schematic flowchart 1 showing the flow of processing when outputting an image in the second embodiment of the present invention. . J... Monochrome multivalued image scanner la... Color multivalued image scanner 2... Input/output image memory, 3.3a... Image area separation section, 4... Separation result memory, 5.5a. - Binarization processing section, 6... Binary image memory, 7... Linear density conversion/inverse conversion section, 8... Multi-value image memory, 9... Binary compression/expansion section, 10. ...Multi-value compression/expansion unit, 11...Monochrome multi-value ratio J printer, 11a...Color multi-value output printer, 12...Optical disk device, 13...Transmission unit, 1
4...Color processing section.・8 do

Claims (5)

[Claims] (1) Image area separation means that separates a binary image area and a multivalued image area of an input image given as multivalued data;
A binarization processing means for obtaining a processed image that has undergone sharpening processing and binarization processing, in which areas other than the value image area are white, and a line for lowering resolution, in which areas other than the multivalue image area are white, for the input image. An image processing device comprising a linear density conversion means for obtaining a processed image subjected to density conversion processing. (2) image area separation means for separating a binary image area and a multivalued image area of an input image given as multivalued data, and further separating the binary image area into a color area and a monochrome area;
Binarization processing means for obtaining a processed image by performing sharpening processing and binarization processing on the input image in accordance with the image area separation result by the image area separation means, in which areas other than black and white binary image areas are made white; Image processing comprising a detailed conversion means for obtaining a processed image in which the input image is subjected to linear density conversion processing to reduce resolution, with the area excluding the multivalued image area and the color binary image area made white. Device. (3) Obtaining a processed image by applying data compression to the image processed by the binarization processing means using the compression method for binary images, and applying data compression to the image processed by the linear density conversion means using the compression method for multivalued images. 3. The image processing apparatus according to claim 1, further comprising multivalue compression means for obtaining a processed image subjected to data compression. (4) Binary decompression means for expanding a data-compressed image by a binary compression means into an image before data compression; multi-value decompression means for expanding a data-compressed image by a multi-value compression means into an image before data compression; Linear density inverse converting means for performing linear density conversion inverse to the linear density conversion by the linear density converting means on the image expanded by the decompressing means, data of an image processed by the linear density inverting means, and an image expanded by the binary decompressing means. 3. The image processing apparatus according to claim 3, further comprising means for synthesizing the data of the image data and the data of the image data. (5) Claim (4) characterized by comprising means for outputting the synthesized image data in a single black color for pixels in a black and white binary image area, and in multiple colors for pixels in other areas. ) image processing device.