JPS63197173A - Color image processor - Google Patents

Abstract

PURPOSE:To prevent picture quality in a halftone part from being deteriorated as far as possible, by identifying the area of a color original, and performing a processing such as color conversion, etc. CONSTITUTION:An area identification circuit 12 compares a result processed by a band-pass filter with a specific threshold value, and decides a picture element having a large value as a character area, and the picture element having a small value as a halftone area. A selection signal (d2) goes to '0' in the halftone area, and '1' in the character area. A signal selection circuit 13 selects signals (r1), (g1) and (b1) for a character and signals (r2), (g2) and (b2) for a halftone corresponding to the selection signal (d2), and generates signals (r1), (g1) and (b1) and sends them to a color image output device 5. In other words, when the selection signal (d2) is set at 1, the signals (r1), (g1) and (b1) for the character are outputted, and when it is set at '0', the signals (r2), (g2) and (b2) for the halftone are outputted. In such a way, since a color in which the color conversion is applied is not outputted to a halftone image even when the image hue of the color original coincides with a designated hue, it is possible to prevent the color at a part other than the character of a color image from being converted even when the color images such as the character, a photography, and print are mixed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to color image output devices such as digital color copying machines and color facsimiles, and in particular to processing such as color conversion for specific colors in color documents. The present invention relates to a color image processing device that performs.

[Conventional technology]

For example, in a digital color copying machine, a color original is read by separating it into three colors, red, green, and blue, to obtain signals for each color, and based on these color signals, yellow is read.

I am trying to output magenta, cyan, and black color materials. For example, for a red portion of a document, yellow and magenta color materials are output in an overlapping manner to reproduce red.

At this time, by changing the correspondence between the colors of the original and the colors of the coloring materials, it is possible to obtain output in a color different from that of the original. By performing such color conversion, when copying a document, for example, it is possible to copy a document written in black using red coloring material to emphasize the document.

Furthermore, when there is a part of a document that you want to emphasize and you want to print it in red letters and copy the document, it is also possible to print or erase only the part in red letters. This is effective in terms of presentations at meetings and security protection.

[Problem that the invention seeks to solve]

However, in conventional color image processing devices,
Color conversion is performed on the entire surface of the document, and specific colors present in the entire document are extracted or erased. Therefore, in the case of a document such as a color image containing a mixture of text, photographs, and prints, parts other than text can also be converted and extracted.

Processing such as deletion will be performed. Therefore, the reproduction of color images also changes significantly, resulting in a drawback of quality deterioration.

In view of the above points, it is an object of the present invention to perform processing such as extraction, deletion, and one-color conversion only on the character portion of a specific color of a color document containing a mixture of color halftone images and color characters. Means and Effects for Solving the Problems] In order to achieve the above object, the color image processing apparatus of the present invention is an apparatus for reading and recording a color original in which a character area and a halftone area are mixed. means for detecting the hue of the color document; and means for identifying each of the regions of the color document;
The present invention is characterized by providing means for extracting or erasing only characters of a specific hue based on the outputs of the means for detecting the hue and the means for identifying the area.

Further, in order to achieve the above object, the color image processing apparatus of the present invention is an apparatus for reading and recording a color original in which a character area and a halftone area are mixed, which includes means for detecting the hue of the color original; It is characterized by providing means for identifying each of the regions of the color document, and means for converting and outputting only characters of a specific hue based on the outputs of the means for detecting the hue and the means for identifying the region. do.

In the present invention, both the hue and area type of a color document are detected. Then, only when the detected hue matches a designated specific color and the area is a text area, the text of that hue is extracted or deleted.

Further, in the second invention, the hue of the detected specific character is converted to another hue and then output.

〔Example〕

DETAILED DESCRIPTION OF THE INVENTION Hereinafter, features of the present invention will be specifically described based on examples with reference to the drawings.

FIG. 2 shows a schematic block diagram of a color image processing apparatus according to an embodiment of the present invention.

In the figure, reference numeral 1 indicates a color image input device using a C0D (charge-coupled device), which separates color document information into three colors of red, green, and blue using a gicroic prism.
It is read as 8-bit grayscale data at a resolution of 60 dots/c+++ (400 dots/inch). Red, green, and blue shading data read by the color image input device 1 is stored in the image memory 2 with 8 bits per pixel. The image memory 2 has a capacity to store one A3 size page of red, green, and blue shading data. The grayscale data from image memory 2 is stored in the color image processing bag W.
3 and provided within the device 3; means for identifying a region of a color image; means for detecting the hue of a color original;
Predetermined processing is performed by filtering means, digital processing means, etc. Details of this color image processing device 3 will be described later. In each of the above devices, signal control of the entire device is performed by a control device 4, and processed signals are supplied to a color image output device 5. This color image output device 5 can, for example, print yellow at a resolution of about 160 dots/cm.

It records four color versions of magenta, cyan, and black. Although an electrophotographic laser beam printer was used here, a color thermal printer, an inkjet printer, etc. may also be used.

Next, details of the color image processing device 3 will be explained with reference to FIG.

Input signals R and G stored in the image memory 2.

B is branched into three routes ■, ■, ■. Route (2) is for processing on the assumption that the human input signal is included in the character area, and route (2) is for processing on the assumption that the human input signal is included in the halftone area. Route (2) identifies the area, and selects and outputs the processing results of routes (2) and (2).

First, route (■) will be explained.

In the figure, 6 indicates a 7-color processing circuit, and this 7-color processing circuit 6 generates 8-bit red manually.

The green and blue color signals R, G, and B are converted into a 1-bit color signal r.
, g, b, yellow, magenta, cyan, black.

The hue of the letters is divided into seven colors: blue, green, and red. Including white, there are 8 colors.

This seven-color processing circuit 6 has a ROM as shown in FIG.
(read-only memory) only. Then, the 8-bit signals R, G, and B are transferred to the ROM61 and RO.
M62. Quantize to -H3 bits using ROM63, and write each signal as a total of 9 bits address.
Call up the contents of OM64, red, green.

It outputs color signals r, g, and b of 1 bit each for blue. In each ROM 61, 62, 63, 64, data for sorting color signals of arbitrary density and arbitrary hue into seven color signals each having a certain level is written as a table.

Furthermore, the seven-color processing circuit 6 may be configured using PAL (programmable array logic) instead of the ROM.

The color signals r, g, b converted into seven colors in this manner are supplied to the hue determination circuit 7. This hue determination circuit 7 determines whether the color signals r, g, and b match the hue specified by the user.

That is, the color signals Sr, Sg, S specified by the user
A logical product is performed between b and the seven-color signals r, g, and b, and when they match, the judgment signal d1 is set to 1, and when they do not match, the judgment signal d1 is set to 0.

The signal selection circuit 8 receives signals r and g obtained by converting the original signal into seven colors.
, b, the converted color signal specified by the user, that is, the converted color signal 1. , 1. , 1. and erasing signals er, el+
eb is supplied. Note that if the paper to be output is white, set e,=e,=eb=Q. This signal selection circuit 8 is composed of, for example, PAL, and selects three types of signals to be described later based on the judgment signal d1 obtained from the hue judgment circuit 7 and the 2-bit processing mode signal m specified by the user. and output it. The processing modes that can be specified by the user are shown in Table 1, and the processing mode signal m
It has four functions depending on the

Table 1 Signals output by the signal selection circuit 8 are shown in Table 2.

Table 2 As can be seen from Table 2, depending on the judgment signal d1 from the hue judgment circuit 7 and the processing mode specified by the user, the
Colorized signals r, g, b, converted color signals t, t, tb specified by the user, and erasure signal e rr
Three types are selected: eto eb.

For example, when the processing mode signal m=oO1, that is, a specified color character is output after color conversion, d.

=1, that is, when the input signal is a specified color character, the converted color signals t, t, tb specified by the user are output. In other words, characters in a color specified by the user are converted to another color specified by the user.

As a result, only the back characters of characters written in red, blue, and black can be replaced with borders or erased, and characters other than blue can be erased.

Here, there are four types of processing modes, but other types of processing are also possible. For example, the number of colors designated by the hue determination circuit 70 may be increased and the determination signal d may be set to 2 bits to switch the conversion depending on a plurality of colors.

On the other hand, in route (2), assuming that the signal is in a halftone area such as a photograph or halftone, the filtering processing circuit 9 removes halftone components that cause moiré using a low-pass filter (not shown).
By removing the color signals R1, G1 . B+
This is converted into pseudo-halftone by the dither processing circuit 10 to obtain 8
Convert bit data to 1-bit data. FIG. 4 shows the coefficients of the two-dimensional FIR (finite impulse response) digital filter used in this example, and FIG. 5 shows the spatial frequency characteristics at that time. From the graph in Figure 5, 1
It can be seen that the halftone dot components from the 33rd line to the 175th line are completely removed. Note that 133 lines and 1751N mean dot densities of 133 Jl) (line pairs)/inch and 133 j'p/inch, respectively.

In path (3), the luminance signal generation circuit 11 generates an 8-bit signal corresponding to the luminance signal Y of the NTSC television signal from the input signals R, G, and B. The luminance signal generation circuit 11 obtains a luminance signal Y using the following equation.

Y = 0.11 B + 0.59 G + 0.3 OR However, the coefficients applied to the signals B, G, and H are not limited to these, since they differ depending on the spectral characteristics of the input device or the purpose.

In this example, from the luminance signal Y obtained in this way, focusing on the fact that the character part contains many mid-range components, the character component is extracted using a band-pass filter. ing. The coefficients and spatial frequency characteristics of the filter actually used are shown in FIGS. 6 and 7.

The area identification circuit 12 compares the results of processing by the band-pass filter with a specific threshold value, and determines that pixels having a large value belong to a character area, and pixels having a small value belong to a halftone area. The selection signal d2 is 0 for halftones and 1 for characters.

In the signal selection circuit 13, according to the selection signal d2 obtained in the above manner, the character signal rIn gl+ b sent on the path ■ and the halftone signal r! +gL b* is selected and signal r3
+ g 3 + b 2 and sent to the color image output device 5.

That is, when the selection signal d is 1, the character signal rl
+ gI+ b+ is output, and when it is 0, a halftone signal ' 21 g 21 b 2 is output.

Therefore, according to the second embodiment, even if the image hue in the color document matches the specified hue, the converted color will not be output for the halftone image, so it will not be possible to output the converted color for the halftone image. Even in the case of a document containing a mixture of color images, the colors of parts other than characters in the color image will not be converted.

Furthermore, since seven-color signals r, g, and b are output for characters other than the specific color, reproducibility is good. That is, since the seven-color processing circuit 6 performs binarization suitable for character reproduction, characters with high contrast can be output.

In addition, since appropriate processing is applied to each of the binary image areas such as characters and halftone image areas such as photographs, it is possible to output high-quality color images.

Note that in the above embodiment, processing such as extraction, deletion, and one-color conversion is performed only on characters of a specific color, but the same processing is performed only on characters with colors other than the specific color. Processing may also be performed.

〔Effect of the invention〕

As described above, in the present invention, since the area of a color document is identified and processing such as color conversion is performed, it is possible to perform processing such as color conversion by identifying the area of a color document. It becomes possible to color convert, extract, and erase only characters with other colors. In other words, since the converted colors are not output for halftone images,
Image quality deterioration in halftone areas can be prevented as much as possible.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a color image processing device according to an embodiment of the present invention, FIG. 2 is a schematic block diagram showing the overall configuration of the color image processing device, FIG. 3 is a block diagram of a seven-color processing circuit, and FIG. 4 5 is a graph showing the coefficients of the filter for removing halftone dots, FIG. 5 is a graph showing the spatial frequency characteristics of the filter for removing halftone dots, and FIG.
The figure shows the coefficients of the bandpass filter for character component extraction.
The figure is a graph showing the spatial frequency characteristics of a bandpass filter for character component extraction. Patent applicant: Fuji Xerox Co., Ltd. Agent: Masu Kobori (and 2 others) Figure 2 Figure 3 M 4 Figure 5 Spatial frequency [Ap/mm]

Claims (1)

[Scope of Claims] 1. In an apparatus for reading and recording a color original in which a character area and a halftone area are mixed, means for detecting the hue of the color original, and means for identifying each area of the color original. and a means for extracting or erasing only characters of a specific hue based on the outputs of the means for detecting the hue and the means for identifying the area. 2. In an apparatus for reading and recording a color original in which a character area and a halftone area are mixed, means for detecting the hue of the color original, means for identifying each of the areas of the color original, and detecting the hue. 1. A color image processing apparatus, comprising: means for color converting and outputting only characters of a specific hue based on the output of the means for identifying the area and the means for identifying the area.