JPH0965143A - Image processor with function of judging kind of map original - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide entirely sharp reproducing images with less moire without imposing burden on a user by controlling the degree of edge emphasis by a spatial filter corresponding to an original judgement result. SOLUTION: A map original judgement circuit 8 for judging whether or not it is a map original is provided in parall to a system for reproducing images, the judgement circuit 8 is operated at the time of pre-scanning or first version image formation and feed-back is performed to a following image formation processing. RGB data linear to the reflectance are inputted from an image input device 1 such as a color scanner to a logarithmic transformation part 2. The RGB data are logarithmecally transformed in the logarithmic transformation part 2 and RGB data linear in density are generated. In a spatial filter 3, an edge emphasis processing is performed to the RGB data. In this case, more than two kinds of the spatial filters 3 are provided and the degree of the edge emphasis to be performed is switched depending on whether or not it is the map original. In such a manner, corresponding to the original judgement result, the degree of the edge emphasis by the spatial filter 3 is controlled.

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,
In particular, the present invention relates to an image processing apparatus that determines whether a document is a map and switches the processing method according to the determination result.

[0002]

2. Description of the Related Art Conventionally, for example, JP-A-63-20523.
As disclosed in Japanese Patent No. 7, there is a method in which a character area and a halftone area are separated and processing is switched. However, although this type of device knows the frequency of the character area in the manuscript, it is impossible to judge whether the manuscript is a map or not, and as a result,
It cannot be used as a device for automatically distinguishing documents.

Further, as a conventional color copying machine, there is one having a mechanism for switching the processing depending on the type of the original, which is classified into four types of originals (character / photo, character, photograph, map) modes. However, the strength of the spatial filter and the screen ruling are switched according to the mode specified by the user by key operation.

In color copiers and the like, in addition to text and photo originals, map originals are also frequently used. Considering the improvement of the image quality of the original, it is preferable to switch the processing between the text original and the map original. This is because, since the map is basically a printed document, it includes a halftone dot portion having periodicity. On the other hand, since there is no such portion in the text original, for example, there is no problem even if strong edge emphasis is applied, but in the former map, moire occurs in the halftone dot portion. Therefore, if the manuscript is found to be a map (different from the character processing), optimum processing can be performed.

Conventionally, a number of devices have been proposed which detect a character area in a document by using an image signal obtained by reading the document with a scanner. For example, JP-A-63-205
In the device described in Japanese Patent No. 237, the character area is detected by utilizing the continuity of pixels, and the processing is switched to the halftone area. Even if an attempt is made to judge a map manuscript from the count value of the character pixels of the whole manuscript using the judgment result of the character / non-character of this device, it is difficult to distinguish between the character manuscript and the map manuscript due to the characteristic quantity. Is.

In other words, not only in such an apparatus, but in the related art, there is no technique for accurately distinguishing and recognizing a map original from other originals. On the other hand, in the color copying machine, there is also a method of allowing the user to specify the "map mode". This is not preferable for making the user feel annoyed and for speeding up.

[0007]

Therefore, the present invention determines whether or not the original is a map original at the time of prescanning,
If it is a map manuscript, it is intended to provide an apparatus that performs a process suitable for the main scan. Further, in a one-drum type color copying machine, an original is determined at the same time when the first plate is imaged. If it is determined that the original is a map original, an apparatus for performing the processing suitable for the second and subsequent image forming processes is provided. It is intended to be provided.

[0008]

According to a first aspect of the present invention, an image reading device reads an original with a digital signal and determines whether the original is a map or not. In the image processing apparatus that switches the processing by the method, the degree of edge enhancement by the spatial filter is controlled according to the result of the document determination.

According to the second aspect of the present invention, the image reading apparatus reads the original with a digital signal and determines whether the original is a map or not, and image processing for switching the processing based on the determination result of the original determining unit. When the apparatus determines that the document is a map, the dither size of the dither processing is reduced.

According to the third aspect of the present invention, the image reading apparatus reads the original with a digital signal and determines whether or not the original is a map, and an image processing for switching the processing based on the determination result of the original determination unit. When the apparatus determines that the document is a map, the error diffusion method is used for processing.

According to a fourth aspect of the present invention, an image reading device reads a document with a digital signal to determine whether or not the document is a map, and image processing for switching the process based on the determination result of the document determination unit. When the apparatus determines that the document is a map, the error diffusion method matrix size is reduced.

According to the fifth aspect of the invention, the determination of the original is made during the prescan.

According to the sixth aspect of the invention, the determination of the original is made at the time of the fast scan accompanied by the image formation of the first plate.

According to the invention of claim 7, the determination of the original is made based on the number of colors in the original.

In the invention of claim 8, the determination of the original is made based on the frequency of the linear pattern in the original.

[0016]

According to the invention described in claim 1, when the manuscript judging means for judging whether the manuscript is a map or not is judged to be the map, the spatial filter for the map manuscript is automatically selected. Then, the degree of edge enhancement by the spatial filter can be controlled.

According to the second aspect of the invention, when the manuscript judging means judges that the manuscript is a map, the means for selecting a specific dithering process from a plurality of dithering processes has different sizes as the halftone process. It is possible to select a dither having a small size for a map manuscript from dither processing of more than one type.

According to the third aspect of the invention, the image processing is switched based on the determination result of the document determination means for determining whether the document is a map or not.
When it is determined that the manuscript is a map, it is possible to select the process by the error diffusion method for the map manuscript.

According to the invention described in claim 4, the image reading device reads the original with a digital signal and determines whether the original is a map or not, and the processing is performed based on the determination result of the original determining means. In the switching image processing apparatus, when the matrix size selecting unit determines that the document is a map, the matrix size of the error diffusion method can be reduced.

According to the fifth aspect of the invention, since the original is determined during the prescan, it is possible to determine the original type during the reproduction of the first plate.

According to the sixth aspect of the invention, since the original is determined at the time of the fast scan accompanied by the image formation of the first plate,
It is possible to obtain images at high speed.

According to the seventh aspect of the invention, since the determination of the original document is made based on the number of colors in the original document, the map original document can be determined with high accuracy.

According to the invention described in claim 8, since the determination of the original is made based on the frequency of the linear pattern in the original, the original can be determined with high accuracy.

[0024]

Embodiments of the present invention will be described below. The present invention is provided with a device for determining whether or not a map original is provided in parallel with a system for reproducing an image, and activates the determination device at the time of pre-scanning or first plate image formation so as to feed back the image forming process afterward. Is. FIG. 1 shows a functional block diagram of a color image processing apparatus to which the present invention is applied. From the image input device 1 such as a color scanner, a linear R
The GB data is input to the logarithmic conversion unit 2. The RGB data is logarithmically converted by the logarithmic converter 2 to generate density linear RGB data. In the spatial filter 3, this RG
Edge enhancement processing is performed on the B data. Here, it is assumed that two or more types of spatial filters are provided, and the degree of edge enhancement to be applied is switched depending on whether or not a map document is used. In this way, the invention according to claim 1 controls the degree of edge enhancement by the spatial filter in accordance with the result of document determination. still,
Details of the embodiment will be described later. Color correction /
The black correction unit 4 converts the RGB signals into complementary YMC signals in consideration of the characteristics of the color image input device and the color image output device.

Color correction methods include a linear neighborhood so-called masking method, a tetrahedral interpolation method, a triangular prism interpolation method, etc., and color correction is performed using these correction methods. At the same time, the K signal is min
It is calculated by multiplying (C, M, Y) by an appropriate multiplier. The UCR unit 5 removes undercolor from the YMC signal to generate a YMCBk signal.

The signal output from the UCR unit 5 is input to the halftone processing unit 6, and the halftone processing unit 6 performs dither processing and density conversion processing suitable for the characteristics of the output device,
The data is sent to the image output device 7. Here, it is assumed that at least two types of dither are provided, and the type (size) of dither to be applied is switched depending on whether it is a map document or not. Also,
Prior to the main scan, during the pre-scan, the map document determination circuit 8 determines whether or not the document is a map document. According to the invention of claim 5, the determination of the document is performed during the prescan in this way.

Next, an embodiment of the map manuscript judgment circuit 8 of the present invention will be described. The map document determining circuit 8 makes a determination by utilizing the fact that the map document has the following features. (1) The number of colors is generally small and limited as compared with natural images. It is a so-called multicolored picture. (2) Many parts are described by lines such as roads, contour lines, and characters. The map manuscript judgment circuit takes the AND of both characteristics and judges whether the read manuscript is a map manuscript. An example of map manuscript determination is shown in FIG. The multicolor image determination block includes the applicant's prior application,
The technique described in JP-A-64-57383 is used. In short, when a multi-color image is read, when the density histogram is taken, the number of colors is limited to some extent, so the peaks and peaks of peaks and valleys and their widths are characteristic. Is.

On the other hand, if the manuscript is a character manuscript, basically, the character manuscript has two peaks of the character color and the white background.
Moreover, the mountain is high and the width is narrow. In addition to this, as a multi-color image determination block, Japanese Patent Laid-Open No. 64-6
The inventions described in JP-A-7689, JP-A-64-62784, JP-A-64-70889 and the like may be used. In either case, it is possible to determine whether or not the image is a multicolor image during prescan. In this way, the invention of claim 7 is such that the determination of the original is made based on the number of colors in the original.

Next, an example of line drawing image determination will be described. FIG. 3 is a block diagram of line drawing image determination, which comprises an MTF correction processing circuit 12, a binarization circuit 13, a pattern matching circuit 14, a line drawing pixel counter 15, and a comparator 16 in order from the input side of the original image data. The basic algorithm of this line drawing image determination is to detect pixels belonging to a line by pattern matching, and to make a determination based on the count value of the pixels corresponding to this line. In this embodiment, the following MTF correction is performed before the binarization process.

Next, binarization is performed with a predetermined threshold value, the binarized data is stored in a line buffer, and a linear portion is locally detected by pattern matching. FIG. 4 shows an example of patterns prepared for line drawing determination, but these are for detecting vertical and horizontal lines, and it is also effective to prepare a pattern for detecting diagonal lines and the like. Further, the pixels subjected to pattern matching are counted over the entire surface of the document and compared with a predetermined threshold value to determine whether or not it is a line drawing. 4A and 4B show an example in which the center pixel is the line drawing pixel in the case of pattern matching (FIG. 4A is the vertical direction, and FIG. 4B is the horizontal direction). direction). As described above, the invention according to claim 8 is such that the determination of the original is made based on the frequency of the linear pattern in the original.

Next, an example of spatial filter switching according to map original / non-map original will be described. Here, for simplification of description, an example in which the processing is switched for each of the non-map originals is assumed to be the same as a general pattern original. The map manuscript becomes an image that is easier to see or read when reproduced with more contrast than a general picture manuscript. However, the map manuscript often includes a halftone dot portion in most cases. Therefore, in consideration of these things, it is preferable to apply a moderate edge enhancement filter. FIG. 5 shows an example of the spatial frequency characteristic of the spatial filter for map originals. In FIG. 5, the vertical axis represents the MTF of the spatial filter, and the horizontal axis represents the spatial frequency.

On the other hand, the spatial filter for general patterns is affected by the dither processing performed later, but a weak edge emphasis filter is further applied than that for the map (spatial frequency and space in this case). The relationship of the MTF of the filter is shown by the solid line B). As a comparison, FIG. 5 shows a spatial filter for a text original (the relationship between the spatial frequency and the MTF of the spatial filter in this case is shown by a solid line C). In this way, the original reading result is read by the image reading apparatus with a digital signal, and the image processing apparatus that switches the processing based on the determination result of the original determination unit and the original determination unit determines whether the original is a map or not. According to the present invention, the degree of edge enhancement by the spatial filter is controlled accordingly.

An example of switching the dither processing according to the map original / non-map original will be described. It is easier to see the map manuscript when the reproduction is given priority over the resolution rather than the gradation. For example, in the case of a printer having a resolution of 400 dpi, 1 dot unit dither is used for the map manuscript and 2 × for the manuscripts that are not. It is sufficient to perform the dither processing of 1 (200 dpi line type). Of course, the size is not limited to this, and if the map original is subjected to a dithering process of a size smaller than that of a general pattern original, it fits the gist of the present invention. As described above, in the image processing apparatus that switches the process based on the determination result of the document determination unit and the document determination unit that determines whether the document is a map by reading the document with a digital signal from the image reading device, the document is a map. When it is determined that the dither processing is performed, the dither size of the dither processing is reduced.

Error diffusion according to map manuscript / non-map manuscript /
An example of switching the dither processing will be described. As a process for playing back images with priority given to resolution for map manuscripts,
Error diffusion type halftone processing is also effective. Generally, the error diffusion method has better resolution than the dither processing having a large size. For example, the map original may be processed by the error diffusion method, and the other originals may be subjected to the 2 × 1 dither processing.

The processing block of the error diffusion method is shown in FIG.
In FIG. 6, the input image data Xij is the quantizer 17
Quantized by, and the output data is input to the error calculation processing unit 18. The data subjected to the error calculation processing is stored in the error buffer, and then each pixel data is weighted in the weighting processing unit 20. In the embodiment of FIG. 6, the threshold value is one binarized value, but it is also possible to provide a threshold value as necessary to provide multi-valued output. Further, although a method similar to the error diffusion method is the minimum average error method, this method may be used for the processing of the map manuscript. As described above, in the image processing apparatus that switches the process based on the determination result of the document determination unit and the document determination unit that determines whether the document is a map by reading the document with a digital signal from the image reading device, the document is a map. When it is determined that there is such an error, the invention according to claim 3 is to perform the processing by the error diffusion method.

An example of switching the error diffusion processing depending on the map original / non-map original will be described. When the map document is reproduced by giving priority to the resolution, there is a method of further improving the resolution in the error diffusion method. This can be achieved by reducing the matrix size when performing the weighting process. An example of the weighting processing matrix is shown below. Therefore, the matrix of two kinds of sizes as described above is prepared, and in the case of a map document, the switching is performed so as to use the small size matrix 1. Of course, the size is not limited to this, and if a weighting matrix having a smaller size than a general pattern original is used for the map original, it fits the gist of the present invention. As described above, in the image processing apparatus that switches the process based on the determination result of the document determination unit and the document determination unit that determines whether the document is a map by reading the document with a digital signal from the image reading device, the document is a map. When it is determined that the error diffusion method is used, the matrix size of the error diffusion method is reduced.

The above is the method of determining whether it is a map original during the pre-scan and switching the processing during the subsequent main scan. For example, in the apparatus for reproducing an image by a so-called frame sequential method of one drum type, the first version is used. It is also possible to determine the document type at the same time as the image formation, and perform the map processing on the second version (if it is a map document). At this time, appropriate processing is performed on the first version, for example, weak edge enhancement for the general pattern or 2 × 1 dither processing. Thus, the invention according to claim 6 is such that the determination of the original is performed at the time of the fast scan accompanied by the image formation of the first plate.

In the present invention, the spatial filter and the dither processing are controlled when it is determined that the original is a map original, but it is also effective to replace the density conversion curve immediately before being printed on the printer with a map. That is, while general patterns aim to reproduce faithfully, the image is processed so that it is easy to see and read, and for example, corrections such as increasing the contrast or corrections such as increasing the density of the highlight part of the map are performed. You may implement. FIG. 7 shows a state in which these are implemented by a one-dimensional table. FIG. 7 shows an example of a density conversion table for a map document. In FIG. 7, a curve P shows a state of increasing the contrast, and a curve Q shows a state of increasing the density of the highlight portion.

The present invention is not limited to the above example, but an image processing apparatus with document type determination, etc., that satisfies the gist of the present invention, that is, an image that determines whether the document is a map and switches the processing method according to the determination result It can be widely applied to processing devices, digital color copying machines and the like.

[0040]

According to the first aspect of the present invention, when the manuscript is determined to be a map, the spatial filter for the map manuscript is automatically selected. It is possible to obtain a reproduced image with little moire.

According to the second aspect of the present invention, two or more types of dither processing having different sizes are prepared as the halftone processing, and when it is determined that the document is a map, the dither having a small size is selected for the map document. Therefore, a sharp reproduced image can be obtained overall without burdening the user.

According to the third aspect of the present invention, when the manuscript is determined to be a map, the process by the error diffusion method is selected for the map manuscript, so that the reproduced image is sharp as a whole without burdening the user. Can be obtained.

According to the invention of claim 4, when it is determined that the original is a map, a small matrix size is selected for the map original, so that a sharp reproduced image is obtained as a whole without burdening the user. You can

According to the fifth aspect of the present invention, since the original is determined during the prescan, the original type can be identified during the reproduction of the first plate.

According to the sixth aspect of the present invention, the original is determined at the time of the first scan accompanied by the image formation of the first plate. Therefore, the image can be obtained at high speed because the prescan is not performed.

According to the seventh and eighth aspects of the invention, since the document type determination is performed based on the characteristics of the map, the map document can be determined with high accuracy.

[0047]

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing an embodiment of a map original determination circuit.

FIG. 3 is a block diagram of line drawing determination.

FIG. 4A is a diagram showing an example in which a (vertical direction) center pixel is set as a line drawing pixel when pattern matching is performed. (B) A diagram showing an example in which the (horizontal direction) central pixel is used as a line drawing pixel when pattern matching is performed.

FIG. 5 is a diagram showing an example of a spatial filter applied to a map original.

FIG. 6 is a processing block diagram of an error diffusion method.

FIG. 7 is a diagram showing an example of a density conversion table for a map original.

[0048]

[Explanation of symbols]

 1 Color Image Input Device 2 Logarithmic Conversion Unit 3 Spatial Filter 4 Color Correction / Black Generation Unit 5 UCR Unit 6 Halftone Processing Unit 7 Color Image Output Device 8 Map Original Judgment Circuit 9 Multicolor Image Judgment Unit 10 Line Drawing Image Judgment Unit 11 AND Circuit 12 MTF correction processing unit 13 Binarization processing unit 14 Pattern matching unit 15 Line drawing pixel counter 16 Comparator 17 Quantizer 18 Error calculation processing unit 19 Error buffer

Claims (8)

[Claims] 1. An image processing apparatus for switching a process based on a determination result of an original determination unit for determining whether an original is a map by reading an original with a digital signal by an image reading apparatus and an original determination An image processing apparatus with map document type determination, characterized in that the degree of edge enhancement by a spatial filter is controlled according to the result. 2. An image reading apparatus reads an original with a digital signal and determines whether the original is a map or not. In an image processing apparatus that switches processing based on the determination result of the original determination unit, the original is detected. An image processing apparatus with map document type determination, wherein the dither size of dither processing is reduced when it is determined to be a map. 3. A document is read in a digital signal by an image reading device, a document determining unit that determines whether the document is a map, and an image processing apparatus that switches processing based on a determination result of the document determining unit An image processing apparatus with map document type determination, characterized in that when it is determined to be a map, it is processed by an error diffusion method. 4. A document is read by a digital signal by an image reading device, a document determining means for determining whether or not the document is a map, and an image processing apparatus for switching processing based on the determination result of the document determining means An image processing apparatus with map document type determination, wherein the matrix size of the error diffusion method is reduced when it is determined to be a map. 5. The image processing apparatus with map original type determination according to claim 1, wherein the original determination is performed during pre-scanning. 6. The image processing apparatus with map original type determination according to claim 1 or 2, wherein the determination of the original is performed during a fast scan accompanied by image formation of the first version. 7. The image processing apparatus with map original type determination according to claim 1, claim 2, claim 3 or claim 4, wherein the determination of the original is performed based on the number of colors in the original. 8. The method according to claim 1, wherein the determination of the original is made based on the frequency of the linear pattern in the original.
An image processing apparatus with a map document type determination according to claim 3 or 4.