JPH04157868A - Color image processor - Google Patents

Abstract

PURPOSE:To perform a reproducing process at a high speed and to decrease the consumption of ink by deciding whether or not there is a black character area in a color document during prescanning operation and omitting black-ink printing operation unless there is a black character in the document. CONSTITUTION:A binary circuit 7 is a circuit which converts a signal K3 into a binary signal according to a specific threshold value and the signal K4b outputted by the binary circuit is inputted to a selecting circuit 8. The selecting circuit 8 selects signals C4a, M4a, and Y4a outputted by a dither circuit 6 as to a picture element area which is decided to belong to a pattern area, and selects the signal K4b for a picture element area of decided picture elements belonging to black characters. A color printer 10 receives the signal from the selecting circuit 8 and reproduces a color image by turning on and off ink dots of the respective colors.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a color image processing device that digitally reproduces color images from a color original. The present invention relates to a color image processing device that reproduces images in three colors: yellow, magenta, and cyan.

[Prior art]

For example, in the case of a color copier, it is preferable to reproduce black characters in a document in a single black color in order to improve the reproduced image quality and reduce ink consumption.

For this reason, for example, the minimum signal MIN (Y, M, C) of each color signal of Y (yellow), M (magenta), and C (cyan) after color correction (masking) of color image data is greater than or equal to a predetermined threshold. The image may be reproduced by monochromatic black processing without applying Y, M, or C ink to the image area.

However, in the case of originals that contain both pictures (halftone images, photographic images) and text, not only the black text but also the picture parts are frequently treated with black monochrome, making it difficult to obtain desirable halftone expressions and playback. Image quality deteriorates.

For the pattern, appropriate undercolor removal processing, so-called UCR (
Under Co1 or Removal processing (for example, 50% UCR processing) is preferable in terms of image quality.

As an apparatus for reproducing only black characters from a color document in monochromatic black, there is a color image forming apparatus described in Japanese Patent Laid-Open No. 63-240175. This device includes a means for extracting a character area using the continuity of pixels at the edge of a character, and a means for detecting black from the minimum signal MIN (Y, M, C) among the Y, M, and C signals after color correction. The black character area is separated by the logical product of the detection results of each means and subjected to monochromatic black processing.

[Problems to be Solved by the Invention] However, with such black character area separation means, halftone dots that are black and have continuous dots like characters with an area ratio of around 50% may be mistakenly determined to be black characters. , In the color halftone image, there are scattered linear or bar-shaped areas where 7% M and C inks overlap, but these areas are also incorrectly determined to be black text areas, resulting in a significant deterioration of the reproduced image quality. was there. Furthermore, since color characters are also subjected to pattern processing, there is a problem in that the resolution of the characters is lost.

Therefore, the applicant separated the black text area, color text area, and picture area from the color document, performed processing for black text on the black text area, and processed the determined text color for the color text area. Reproduction processing and Y, M, C, B for the picture area
We have already proposed a color image processing device that processes images using four colors.

By the way, as mentioned above, for the picture, Y, M, C
, Bk, but it is known that a certain level of image quality can be obtained even with three colors, Y, M, and C. Proceedings of the 84th Spring Research Presentation of the Japan Society of Printing, pp.
H9-122).

However, in conventional color image processing devices such as color copier devices, the printing process of Y, M%C, and Bk is repeated four times even if there are no black characters in the document.
That is, there is a drawback that high speed cannot be achieved because black (Bk) ink is printed.

An object of the present invention is to detect the presence or absence of a black character area during pre-scanning, and to detect the presence or absence of a black character area in a color document by 7%
, C, and C color inks at high speed.

[Means for Solving the Problem] In order to achieve the above object, the present invention digitally reads a color original and digitally prints the read color image data using yellow, magenta, cyan, and black inks. A color image processing device for reproducing a color image, comprising means for separating the color original data into a character area and a picture area, a means for determining the color of a local area in the color original data, and a means for separating the color original data. A black character detection means detects a black character area in response to the output of the color determination means, and if the detection means does not detect black characters in the color document during prescanning, the picture area is covered with yellow, magenta, and cyan ink. It is characterized by being recycled.

[Function] If it is determined that there are no black characters in the document during pre-scanning, reproduction processing is performed using only Y, M, and C inks according to the control signal from the black character detection means during main scanning.

On the other hand, if there are black characters in the document, during the main scan, a control signal from the black character detection means is used to process black characters (single black color) and pattern (Y, M) for each pixel.

C) Switch processing.

[Example] Hereinafter, an example of the present invention will be specifically described using the drawings.

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

The color scanner 1 has a photoelectric conversion element such as a CCD camera, and reads a color original to display R (red), G (green), and B.
Outputs color separation signals of three colors (blue). A/D converter 2
converts the R, G, and B signals into, for example, 8-bit digital signals.

The log converter 3 converts the R, G, and B digital signals into a signal CI representing the amount of each color ink of C (cyan), M (magenta), and Y (yellow).

Output Ml and Yl. The masking circuit 4 performs color correction (masking) on the CI, M1, and Y1 signals in order to remove the turbidity component of the color separation filter of the input sensor 1 and the turbidity component of the ink, and outputs the C2, M2, and Y2 signals. This color correction is performed, for example, by the following equation.

Y2=11XY1+K12XMl+13XCIM2
21 C3, M3, Y by removing part or all of the C2, M2, and Y2 signals that represent the quantities.
3 signal and a signal of 3 for the amount of black ink equivalent to removal. Here, UCR processing A (black character area processing) and UCR processing B (picture area processing) can be selected as the UCR processing.

UCR processing A generates a K3 signal in the case of a black character.

In the example of 0CR100% in black text, if the Y2, M2, and C2 signals are input, the value obtained by subtracting 100% of the MIN (C2°M2.Y2) signal from the C2, M2°Y2 signal is 0.
3. M3. Y3, and K3 is MIN (C2, M2.
Y2).

OCR processing B for the picture area is MIN(C2°M2.Y
2) The value obtained by subtracting, for example, 50% of the signal from the C2, M2, Y2 signal is C3, M3. It becomes Y3, and K3 is MIN
This is a so-called 50% OCR process that generates a signal having a value of (C2, M2.Y2).

Then, according to a control signal from a black character detection device 9 (FIG. 2), which will be described later, UCR processing A for character areas is selected for pixel areas determined to be characters, and UCR processing A for character areas is selected for pixel areas determined to be patterns. Select UCR processing B for.

The dither circuit 6 includes C3, M3 . This is a circuit that binarizes the Y3 and K3 signals by systematic dithering, and its output signal C
4a, M4a, Y4a, 4a is input to the selection circuit 8.

The binarization circuit 7 is a circuit that binarizes the K3 signal using a predetermined threshold value, and 4b is input to the selection circuit 8 as a signal output from the binarization circuit.

The selection circuit 8 selects signals C4a and M4a output from the dither circuit 6 for pixel areas determined to belong to a picture area by a control signal from a black character detection device 9, which will be described later.
, Y4a is selected, and for pixel areas determined to belong to black characters, 4b is added to the signal output from the binarization circuit 7.
Select.

In the color printer 1o, a color image is reproduced by receiving a signal from a selection circuit 8 and turning on/off ink dots of each color.

FIG. 2 is a block diagram of the black character detection device 9 of the present invention. In the present invention, black characters are detected during pre-scanning (which is performed on board to determine whether the document is black and white or in color, to detect the size of the document, etc.).

A color original is read by a color scanner L, and R
The signal becomes color separation signals of three colors (red), G (green), and B (blue) and is input to the color determination circuit 21 and the character detection circuit 22.

The color determination circuit 21 is a circuit that determines the color of the pixel of interest or block of interest, especially whether it is black or not.
, G, and B data are compared with respective predetermined threshold values, and if R>threshold r, G>threshold g, and B>threshold, then black is determined. In addition, in the case of the block of interest, R, G,
After taking the average for each B, compare it with a predetermined threshold,
Determine color.

The character detection circuit 22 is a circuit that extracts a character area from a color document, and this character detection circuit receives R, G, and B signals (linearly combined α
Input R+βG+γB signal or max (R, G, B) signal). Here, α, β, and γ are coefficients, which are determined through experiments or the like.

In this embodiment, a pixel area where a part of a character and a part of a white background continuous with the character coexist is detected from the αR+βG+γB signal. That is, the input signal is binarized into low level/non-low level using a predetermined threshold value, and then inputted to a low level pixel pattern matching circuit, for example, the low level in a 3 x 3 matrix with the pixel of interest as the center pixel. /When a non-low level pattern and a predetermined pattern are matched,
The pixel of interest is detected as a character low-level pixel.

In addition, the input signal is binarized into high level/non-high level using a predetermined threshold value, and then input to a high level pixel pattern matching circuit. When the level/non-high level pattern matches a predetermined pattern, the pixel of interest is detected as a character high level pixel.

Then, if there are a certain number of high-level pixels and low-level pixels at the same time in the vicinity of the pixel of interest, the pixel of interest or its block is determined to be a character area. Hei 2-11835
This was proposed as No. 8).

The black character detection circuit 23 determines a black character area as a black character area based on the outputs from the color determination circuit 21 and the character detection circuit 22.

The counter 24 counts the black character pixels of the entire document during pre-scanning, and determines that there is no black character in the document if the count value is less than a predetermined value. Then, the presence or absence of a black character ("1"/"O") is stored in a buffer (not shown), and if there is no black character (0), no process of printing black ink is performed.

Since the present invention is configured as described above, when it is determined that there are no black characters in the document during pre-scanning, the selection circuit 8 selects C4a and M4a according to the control signal from the black character detection device 9 during main scanning.

Y4a is selected, and the color printer 9 performs three printing processes of Y, M, and C.

On the other hand, if there are black characters in the document, during the main scan, the selection circuit 8 processes black characters (single black, K4b) and pictures (Y,
M, C) Switch processing.

Therefore, the black character area is reproduced (printed) in a single color of black, and if there is no black character in the original, Y.

The pattern is processed using three colors, M and C.

[Effects of the Invention] As described above, according to the present invention, the presence or absence of a black character area in a color document is determined during prescanning, and if there is no black character in the document, black ink is not printed. It can be played back faster than the
Furthermore, ink consumption can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a block diagram of a black character detection device of the present invention. 1... Color scanner, 2... A/D converter,
3...log conversion circuit, 4...masking circuit,
5...OCR circuit, 6...Dither circuit, 7...
Binarization circuit, 8... Selection circuit, 9... Black character detection device, 10... Color printer, 21... Color determination circuit, 22... Character detection circuit, 23... Black character detection circuit .

Claims (1)

[Claims] (1) Digitally read a color original and use the read color image data as yellow, magenta, cyan,
In a color image processing device that digitally reproduces a color image using black ink, means for separating the color original data into a character area and a picture area, and determining the color of a local area in the color original data. black character detection means for detecting a black character area in response to the outputs of the separation means and the color determination means; A color image processing device that performs reproduction processing using yellow, magenta, and cyan inks.