JP3121026B2 - Color image processing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image processing apparatus for processing a color image signal obtained by reading a color original image, for example.

[0002]

2. Description of the Related Art The configuration of a conventional color image copying apparatus is shown in FIG.
Shown in In such a color image copying apparatus, a color original image is separated into R, G, and B color signals by a CCD, read, converted into digital signals, and then logarithmically converted (L).
OG), masking conversion, inking (UCR), and the like to form color image data consisting of Y (yellow), M (magenta), C (cyan), and K (black), and output to the printer. To form a color image.

[0003]

However, in the prior art, the sensitivity of the CCD sensor for reading a color image varies, the amount of light for irradiating a document image varies, or the image reading unit and the printer unit are not connected to each other. If the color characteristics are different, the color of the output image will be different from the original image even if the same R, G, B image information is input. For example, if the image reading unit is a color reader of a copier and the image output unit is a display device such as a color CRT, the color characteristics are different between input and output devices of these image data, so that the image data may be displayed in a different color from the original image. May be. For this reason, there has been a problem that some means for correcting image data must be provided between the image input unit and the image output unit, and the user must perform color adjustment and output.

Therefore, between the image input unit and the image output unit,
If signals are exchanged using a standardized signal,
There is no need to correct for variations in color characteristics between these devices
Become. Therefore, as such a standardized signal, C
IE L^* a^* b^* Signal or L ^* u^* v^* Using signals, etc.
Image signal exchange between the image input unit and the image output unit
Conceivable. But L^* a^* b^* Signal or L^* 
u^* v^* Precise conversion when converting image data to signals
Erroneous in the feature amount (eg, edge amount) of the image data.
There is a possibility that the difference may enter, and the contrast of the read image may be reduced.
Output images that are displayed after being adjusted or smoothed
There was a problem that the processing of was not performed effectively.

The present invention has been made in view of the above-mentioned conventional example, and when converting an input standardized color image signal into a density signal, the color balance is adjusted according to the gray level of the original color image signal. Accordingly, an object of the present invention is to provide a color image processing apparatus capable of outputting an image without impairing the characteristics of the original color image signal. Another object of the present invention is to convert an input standardized color image signal into a density signal by performing edge enhancement in accordance with an edge of the original color image signal without impairing the characteristics of the original color image signal. An object of the present invention is to provide a color image processing device that outputs an image.

[0006]

In order to achieve the above object, a color image processing apparatus according to the present invention has the following arrangement. That is, input means for inputting a standardized color image signal converted from a color image signal to a standardized color image signal, inverse conversion means for inversely converting the standardized color image signal to an original color image signal, and the inverse conversion means Extraction means for extracting the gray level of the original color image signal based on the minimum value of the inversely converted RGB signal of the color image signal, and conversion for converting the standardized color image signal input by the input means into a density signal Means, and a color balance adjusting means for adjusting a color balance of the density signal converted by the converting means based on the gray level extracted by the extracting means. In order to achieve the above object, a color image processing apparatus of the present invention has the following configuration. That is, input means for inputting a standardized color image signal converted from a color image signal to a standardized color image signal, inverse conversion means for inversely converting the standardized color image signal to an original color image signal, and the inverse conversion means Extracting means for extracting an edge of the original color image signal from the inversely converted color image signal; converting means for converting the standardized color image signal input by the input means into a density signal; Means for performing edge enhancement on the density signal converted by the conversion means based on the edge.

[0007]

In the above arrangement, a standardized color image signal converted from a color image signal to a standardized color image signal is input, and the standardized color image signal is inversely converted into an original color image signal. The gray level of the original color image signal is extracted based on the minimum value of the RGB signal of the color image signal inversely converted in this manner, and the density signal obtained by converting the input standardized color image signal based on the gray level In order to adjust the color balance. Further, according to the configuration of the present invention, a standardized color image signal converted from a color image signal to a standardized color image signal is input, and the standardized color image signal is inversely converted into an original color image signal. An edge of the original color image signal is extracted from the inversely converted color image signal, and based on the edge, an operation is performed to perform edge emphasis on the density signal obtained by converting the input standardized color image signal.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. <Description of Configuration of Color Copier (FIG. 1)> FIG. 1 is a block diagram showing the configuration of the image processing unit of the color copier of this embodiment. In the figure, A indicates an image input unit, and B indicates an image output unit that reproduces an image based on a signal from the image input unit A.

First, the configuration of the image input unit A will be described.
Denotes a CCD sensor which converts optical information of a document image into R, G, B signals and reads the signals. The image signal read by the CCD 1 is sampled and held by the sample and hold circuit 2 for each pixel. The sampled and held analog signal is converted into a digital signal by the A / D converter 3 and then subjected to shading correction by the shading correction circuit 4 based on white data stored in advance. As a result, variation in output due to variation in sensitivity between the light receiving elements of the CCD 1 is corrected, and the output is normalized to a predetermined number of bits. The signal subjected to the shading correction in this manner is L ^* a ^* b ^* by the standardization circuit 5 based on the following equation ^.
Converted to a signal.

First, when the read signal is NTSC R, G, B
For color signals, tristimulus values X, Y, Z in the X, Y, Z color system
Is converted to

[0011]

(Equation 1) Next, the following operation is performed for conversion to the L ^* a ^* b ^* color system.

L ^* = 116 · (Y / Y ₀ ) ^1/3 -16 a ^* = 500 · [(X / X ₀ ) ¹ /3-(Y / Y ₀ ) ^1/3 ] b ^* = 200 · [(Y / Y ₀ ) ¹ / ^3- (Z / Z ₀ ) ^1/3 ] X ₀ , Y ₀ , Z ₀ ... Constants These calculations are performed in the standardization circuit 5 by matrix calculations. This is shown in the color space coordinates shown in FIGS.

The signal L ^* a ^* output from the image input unit A
The signal b ^* is sent to the image output unit B. Image output section B
Then, the signal L ^* a ^* b ^* from the image input unit A is converted into a density conversion circuit 6. To convert into yellow (Y), cyan (C), and magenta (M). At this time (lookup table) L
Conversion by UT is performed. The signal L ^* a ^* b ^* from the image input unit A is converted into R, G, B data by the inverse conversion circuit 7. The inverted signals R, G,
For B, the feature amount extraction circuit 8 detects the gray amount. Here, the minimum value of R, G, and B is defined as a gray amount, and this gray amount represents an achromatic color. After the color balance of the target pixel is adjusted by the color balance circuit 9 based on the gray amount thus obtained, the image signal is converted into Y, M, C, and K image signals, and output to the image forming unit 10 to reproduce the image. <Second Embodiment> FIG. 2 is a block diagram showing the structure of an image output unit B 'according to another embodiment of the present invention.
Portions in common with are denoted by the same numbers. Reference numeral 21 denotes an edge extraction unit which extracts an edge signal e as extraction of a feature amount of image data from an RGB signal obtained by inversely transforming the signal L ^* a ^* b ^* from the image input unit A. Comparator 2
2 receives the signal L ^* a ^* b ^* and the edge signal e, and outputs the signals L, a, b and e ′ to the density conversion circuit 23. The density conversion circuit 23 calculates YM from these L, a, and b signals.
A signal C is generated and output, and an edge signal e ″ is output.
, And the signal amounts of Y, M, and C are compared. Here, when the amount of K (black) is larger than the threshold Th, the edge amount e ″
Is added to the image signal to sharpen K (black).

As described above, according to the present embodiment,
Output signal from the image input unit that reads color images
Signal L^* a^* b^* And L in the image output unit^* a
^* b ^* Density conversion circuit for converting data into Y, M, C, (K)
Is provided. Also, L in the image output unit^* a^* b^* Signal
To provide an inverse conversion circuit that performs inverse conversion to R, G, B signals
Therefore, for the standard image signal from the image input unit,
At the output unit, match using the features of the image
It becomes possible.

[0015]

As described above, according to the present invention, when converting an input standardized color image signal into a density signal, the color balance is adjusted according to the gray level of the original color image signal. Thus, an image can be output without deteriorating the characteristics of the original color image signal. Further, according to the present invention, when converting the input standardized color image signal into a density signal, by performing edge enhancement according to the edge of the original color image signal, without impairing the characteristics of the original color image signal. There is an effect that an image can be output.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an image processing unit of a color copying machine according to an embodiment.

FIG. 2 is a block diagram illustrating a configuration of an image output unit according to another embodiment of the present invention.

FIG. 3 is a block diagram illustrating a configuration of an image processing unit of a conventional color copying machine.

FIG. 4

FIG. 5 is a diagram illustrating an example of color space coordinates.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 CCD sensor 2 Sample / hold circuit 3 A / D converter 4 Shading circuit 5 Standardization circuit 6,23 Density conversion circuit 7 Inverse conversion circuit 8 Feature extraction circuit 9,24 Color balance circuit 10 Image forming section 21 Edge extraction circuit

Claims (3)

(57) [Claims] An input unit for inputting a standardized color image signal converted from a color image signal into a standardized color image signal; an inverse conversion unit for inversely converting the standardized color image signal into an original color image signal; R of the color image signal inversely converted by the conversion means
Based on the minimum value of the GB signal,
Extracting means for extracting a gray level ; converting means for converting a standardized color image signal inputted by the input means into a density signal; and extracting means for extracting a gray level based on the gray level extracted by the extracting means.
For the density signal converted by the conversion means.
A color image processing apparatus comprising: a color balance adjusting unit that adjusts a balance . 2. A standardized color image signal from a color image signal.
Input means for inputting a standardized color image signal
And transforming the standardized color image signal back to the original color image signal.
Inverse converting means for converting the color image signal inversely converted by the inverse converting means.
Extraction means for extracting edges of the original color image signal
And the standardized color image signal input by the input means.
Conversion means for converting the density signal, before on the basis of the edges extracted by the extraction means
Edge intensity for the density signal converted by the conversion means.
Color image processing apparatus characterized by having the means for performing tone. 3. A standardized color image signals input by the input means, the color image processing apparatus according to claim 1 or 2, characterized in that RGB signal is normalized color image signal.