JP2618893B2 - Color image processing equipment - Google Patents

Description

Description: Object of the Invention (Industrial application field) The present invention relates to an apparatus for reading a color original and performing image processing, and particularly relates to a change in spatial frequency characteristics and an area based on image characteristics. The present invention relates to an apparatus that performs a detection process.

(Prior Art) Conventionally, when converting spatial frequency characteristics of a color image to remove noise or improve sharpness, or when performing area identification based on the properties of an image such as a binary / halftone image. Is
In many cases, processing is performed using three-color separated color signals (for example, red (R), green (G), and blue (B)), or luminance and color difference signals.

For example, when performing with luminance and color difference signals (Japanese Unexamined Patent Publication No.
77) Independent processing is possible for each, and when low-pass processing is applied to the color difference signal and high-frequency enhancement processing is applied to the luminance signal, color noise can be reduced and only sharpness can be improved. There were advantages such as becoming.

However, the above processing increases the color noise at the edge of the pattern, so if the S / N ratio of the sensor improves,
The disadvantages are greater than the above advantages. Further, the signal processing circuit must simultaneously process signals for three colors (luminance signal, color difference signal 1, color difference signal 2), which has a disadvantage that the circuit scale becomes large and complicated.

Further, in the case of performing a region identification process between a binary image such as a character and a halftone image, it is possible to identify even a process using only a luminance signal. However, in the case of different colors having the same brightness, for example, it is impossible to detect a character or the like recorded in black on a red background color.

Next, the color signals (R, G, B) of the three color separations are converted into three color signals (yellow (Y), magenta (M), and cyan (C)) of the amount of ink, and the spatial frequency characteristics are respectively independent of each other. Example of processing of area and area identification processing (JP-A-59-9987)
5) There is. In this case, there is an advantage that the processing can be performed independently for each color. However, since independent circuits for three colors are required, there is a disadvantage that the circuit scale becomes large and complicated.

(Problems to be Solved by the Invention) As described above, a conventional apparatus which performs spatial frequency processing on a signal converted into luminance and color difference signals and a signal converted into ink amounts of three colors at the same time may not be able to detect color characters. And the circuit system becomes complicated.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a color image processing apparatus capable of reducing the circuit scale to reduce complexity and identifying regions even for a character pattern in which only the hue is changed.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a method of separating a color image into n colors and reading the image.
(N-1) The color conversion is performed for the colors, and the signal is subjected to spatial frequency characteristic processing and area identification processing for character images and halftone images. It is characterized by having means for obtaining a color signal of one or two colors including a color component a plurality of times from the color signals of n simultaneous colors and performing the above processing.

(Operation) The present invention obtains one or two color signals including color components from a signal obtained by color-separating a color image into n colors and performs processing of spatial frequency characteristics and area detection processing. Thus, only one-color or two-color signal processing is performed at the same time. Therefore, the circuit becomes easy. In addition, since a color component is included, it is possible to identify an area of a pattern having a change in hue. By sequentially performing this processing in a time series so as to match the output device, full-color processing can be performed.

(Embodiment) An embodiment of the present invention will be described below with reference to FIG.

The color signals R, G, and B are read from the color sensor 101, and are converted into digital signals by the AD converter 102. Next, the standardization circuit 103 corrects unevenness in sensitivity of the color sensor and unevenness in the illumination system. This circuit is also called a shading correction circuit, and is realized by, for example, a circuit described in Japanese Patent Application No. 59-192663. That is, correction of sensitivity unevenness and the like is performed by being standardized by a signal obtained by reading a white reference plate. The standardized signal is input to the color conversion circuit 104. The details of the color conversion circuit 104 include the circuit shown in FIG.

In this circuit, the ink amount signals Y, M, C, K
Convert to That is, the processing of the following equation is performed.

In this color conversion circuit, the calculations of Y, M, C, and K in the above equations are performed separately. For example, the color sensor 101 is a mechanical scanner for sub-scanning, and when the output signal of the color image processing apparatus is color-sequentially output in a frame-sequential manner as in a thermal transfer color printer or a laser color printer, the first scanning is performed next. , The calculation is sequentially performed in the order of C and K, as in the case of only the Y in the above equation, and only the M in the next second scan. For example, a case where Y is calculated will be described. The R signal is input to the ROM 202 from the signal line 201. ROM 202 contains f _YR , f _YG , f _YB , f _MR ,
Nine functions (tables) of f _MG , f _MB , f _CR , f _CG , f _CB , f _KR , f _KG , and f _KB are stored. First, the table f _YR is selected from the switching control line 203 and the density is selected. Function conversion. Note that the control line 203 is controlled by a CPU and a clock controller not explicitly described here.

Next, the converted value is input to the adder 204 and output to the latch 205. Next, a G signal is input to the signal line 201. Then, the table f is switched by the switching control line 203.
_YG is selected and converted. This value is input to the adder 204, f _YR (R) + f _YG (B) is calculated, and output to the latch 205. Next, the B signal is input to the signal line 201, the table _fYB is selected by the switching control line 203, and the data is converted. When this value is input to the adder 204, f _YR (R)
+ F _YG (G) + f _YB (B) is calculated, output to the latch 205, and stored in the latch 207 by the control line 206. At this time, the latch 205 is cleared to zero by the control line 208.

Now, the signal stored in the latch 207 is input to ROM 209, a table g _Y is selected by the control line 210,
It is converted into ink amount data Y. That is, Y in equation (1) is calculated. In this way, Y is the signal (R, G, B)
Is calculated one for each set of. Therefore, during one sub-scan, Y is sequentially calculated for each pixel. The signal converted into the ink amount in this manner is calculated from a pair of three signals (R, G, B) as shown in Expression (1). That is, when a color signal is transmitted to the printer, a single color signal may be used as the ink amount signal of the printer. However, if the signal is not converted into a signal of the ink amount of the printer, a signal of three colors is generally required. At the next second scan, M is calculated instead of Y.

The signal thus converted into the ink amount enters the low-pass processing circuit 105 shown in FIG. Here, for example, 3 × 3 pixel averaging processing is performed. This output is a low-pass signal. The low-pass processing is realized by the circuit shown in FIG. That is, they are sequentially input to the three line memories 301, 302, and 303 for each line. Next, the data is read from the line memories 301 and 302, added by the adder 304, and read from the line memory 303 and added by the adder 305. Next, the added data is sequentially recorded in the latches 306, 307, and 308. The data of the latches 306 and 307 are added by an adder 309, and the contents of the latch 308 are added by an adder 310 and output. That is, an addition result of the neighboring 3 × 3 images is obtained.
Next, 1/9 division is performed. The data is input to the data conversion ROM 311, and the average value of 3 × 3 pixels is calculated. Thus 3 × 3
, Three lines of memory are required. The averaged signal is subtracted from the original signal by an adder 10.
Find the difference by 6. This value is referred to as the Laplacean signal. This signal is further multiplied by a constant coefficient K by the ROM 107 and added to the original data by the adder. That is, if the original data is Y and an averaged signal is used, the output X of the adder 108 is given by the following equation.

X = Y + K (Y-) (2) This signal X is a signal in which the high frequency component is emphasized.

Next, the character area determination will be described. The output of the adder 106 is a Laplacian signal of the image signal, and the area is determined based on this signal. This region discrimination is performed based on a binarized pattern of the Laplacian signal of 3 × 3 pixels in the vicinity. That is, the determination is made by pattern matching.
Japanese Unexamined Patent Publication (Kokai) No. 60-204177 discloses a specific circuit configuration for a luminance signal. Although the present embodiment is a process performed on the ink amount after color conversion, it is basically a processing circuit substantially similar to the circuit configuration of the above-mentioned application. The details are shown in FIG. The Laplacian signal output from the adder 106 in FIG. 1 is input to the binarization ROM 401 in FIG. ROM401
Performs binarization above a certain level,
The data is sequentially recorded in the line memories 403, 404, and 405 having a 1-bit configuration via the line 402. The signals recorded in the line memories 403, 404, and 405 are read out by three neighboring pixels and input to the ROM 406. The ROM 406 outputs a character discrimination signal at the time of a character-like combination (at the time of addressing).

As described above, the low-pass processing, the high-frequency emphasizing processing, and the character area identification processing circuit described above do not have a plurality of processing circuits for each color signal, but have only one processing circuit. Change the parameters for each scan,
Each color, Y, M, C, and K can be handled, and can be processed by the same common circuit. Therefore, the circuit is extremely simple because only one color circuit is required. Also, in this circuit, since the area is determined by the color ink amount signal, unlike the conventional processing using only the luminance signal,
Characters having the same brightness but different colors can be identified.

Next, another embodiment of the present invention will be described with reference to FIG. In this embodiment, the color sensor 101, the AD converter 10
2. The normalization circuit 103 is the same as in the previous embodiment.

The color conversion 504 is a circuit shown in FIG. 6, and is basically the same as that of FIG. 2, but in this embodiment, the color signal and the luminance signal I are calculated simultaneously. The luminance signal I is calculated by the following equation.

I = R + G + B (3) Therefore, by providing only the latch 605 with the configuration shown in FIG. 2, it is possible to simultaneously calculate the ink amount signal and the luminance signal. The color-converted signal and the luminance signal are subjected to low-pass processing by a low-pass circuit 505. Low-pass circuit 505
Is a configuration having two circuits of FIG. The low-pass processed signal is added to the adder 10 as in the previous embodiment.
6. The multiplication table 107 and the adder 108 convert the ink signal into a high-frequency emphasized ink amount signal. Next, the ink amount signal of the Laplacian output signal of the adder 106 is input to the discrimination circuit 109, and a discrimination signal is output as in the previous embodiment. On the other hand, the Laplacian signal of the luminance signal is also output from the adder 106 at the same time, and this signal is input to the determination circuit (2) 510. The processing of the discrimination circuit (2) 510 is the same as that of the discrimination circuit (1) 109, but performs character discrimination on the luminance signal. Next, a signal obtained by performing a character determination on the color ink amount signal and a signal obtained by performing a character determination on the luminance signal are input to the comprehensive determination ROM 511. The comprehensive determination ROM 511 performs comprehensive determination based on a combination of the two determination results and outputs the result.

In this embodiment, unlike the previous embodiment, the color conversion circuit 50
4 and a circuit such as the low-pass processing circuit 505, the discriminating circuit (2) 510, and the comprehensive discriminating circuit 511, which are complicated. However, regardless of the color conversion output signal (for example, Y), the determination based on the luminance signal is also performed at the same time. , M when the tone is determined to be halftone).

〔The invention's effect〕

As described above, in the present invention, after performing the color conversion, the spatial frequency processing such as the low-pass processing and the high-frequency emphasis and the character area determination processing are performed on the ink amount signal. It is only necessary to process a single signal of the ink amount, and it is not necessary to have a circuit for a plurality of color signals. Therefore, the circuit becomes extremely simple and adjustment and the like become easy.
Further, since the determination is made based on the ink amount signal, even if the underground color is the same as the brightness, characters, patterns, and the like composed of different colors can be identified.

[Brief description of the drawings]

FIG. 1 is a diagram showing an entire embodiment of the present invention, FIG. 2 is a diagram showing a color conversion circuit, FIG. 3 is a diagram showing a low-pass processing circuit, FIG. FIG. 11 is a diagram showing the entirety of another embodiment of the present invention, and FIG. 6 is a diagram showing a color conversion circuit of another embodiment. 101: color sensor, 102: AD converter, 103: standard circuit, 104: color conversion circuit, 105: low-pass processing circuit,
106, 108 ... Adder, 109 ... Discrimination processing circuit.

Claims (3)

(57) [Claims] 1. A color image is read after being separated into n colors.
(N-1) For a color signal color-converted below the color,
A color image processing apparatus for performing spatial frequency characteristic processing and binary / halftone image area identification processing. 2. The method according to claim 1, wherein said color conversion is conversion from a dot-sequential color signal or a simultaneous n-color signal to a simultaneous one-color plane-sequential color signal.
Item 7. The color image processing apparatus according to Item 1. 3. The color conversion is a conversion from a dot-sequential color signal or n simultaneous color signals to two sets of color signals, one of the two sets of color signals including a luminance signal. 2. The color image processing apparatus according to claim 1, wherein