JPH07177366A - Color image processor - Google Patents

Abstract

(57) [Summary] (Correction) [Purpose] To make a transitional color inconspicuous and obtain a good color conversion image. [Arrangement] An input color image signal composed of color separation signals of three colors is converted by a coordinate conversion unit into a tint multivalued signal represented by hue, saturation, and lightness. The color tone multi-valued signal obtained by the conversion is converted into another color tone multi-valued signal designated in advance by the lookup tables 109 to 111, and the color tone multi-valued signal obtained by the conversion is subjected to coordinate inversion. Converter 1
At 12, the color separation signals of three colors are restored.

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, and more particularly to a color image processing apparatus having a function of replacing a specific color in a document with another color.

[0002]

2. Description of the Related Art FIG. 6 shows a conventional color image processing apparatus.

The three-color image signals red (R), green (G), and blue (B) are converted into a luminance signal I, a hue signal H, and a saturation signal S by the matrix calculation of the coordinate conversion section 61. . Then, the comparators 62a to 62f
Then, each of the three signals is compared with I, H, and S of the color set as the conversion target. As a result of the comparison, when the difference between the three colors is less than or equal to the predetermined value, the color of the image is replaced by the “converted color” preset as the “color to be converted” by the selector 63. On the other hand, if any of them is far from the predetermined value, the selector 63 outputs the document color as it is.

[0004]

In the above-mentioned conventional example, the pre-conversion and post-conversion colors are switched by the binary information indicating whether or not the color of the document corresponds to the "conversion target color". For this reason, in the portion of the color near the boundary close to the color to be converted, the color before and after conversion remains uneven due to chattering due to uneven reading and the like, which may result in an unsightly image.

In view of the above-mentioned conventional example, an object of the present invention is to provide a color image processing apparatus capable of obtaining a smooth color-converted image even in the tint of a boundary.

[0006]

1) A color image processing apparatus according to the present invention uses an input color image signal composed of color separation signals of three colors to express a large amount of tint represented by hue, saturation, and lightness. Coordinate conversion means for converting into a value signal, tint conversion means for converting the multi-valued tint signal obtained by conversion by the coordinate conversion means into another pre-designated multi-valued hue signal, and tint conversion means And a coordinate reverse conversion means for returning the multi-valued tint signal obtained by the conversion into a color separation signal of three colors.

2) The color image processing apparatus described in 1) above is characterized in that the tint conversion means is a table reference means.

3) The color image processing apparatus described in 1) above is characterized in that the tint conversion means is an arithmetic means.

4) The color image processing apparatus described in 1) above further includes area designating means for designating a specific area, and the tint conversion means is a conversion type for each area designated by the area designating means. It is characterized by switching.

5) In the color image processing apparatus described in 1) above, the determining unit determines whether the tint is changed by the tint converting unit, and if the determining unit makes a negative decision,
Switching to the input color image signal, and when a positive determination is made, switching means for switching to the color separation signals of the three colors from the coordinate reverse conversion means is provided.

6) The color image processing apparatus described in 1) above is further characterized by further comprising display means for temporarily displaying an image whose color is converted.

[0012]

According to the present invention, the input color image signal composed of the color separation signals of the three colors is converted into the hue,
Saturation, and converted into a tint multivalued signal represented by lightness, the tint multivalued signal obtained by the conversion, by tint conversion means,
The color tone multi-valued signal is converted into another color tone multi-valued signal designated in advance, and the color tone multi-valued signal obtained by the conversion is returned to the color separation signal of three colors by the coordinate reverse conversion means.

In the present invention, the conversion type is switched by the tint conversion means for each area designated by the area designating means.

In the present invention, the determining means determines whether or not the tint has changed by the tint converting means. If a negative decision is made, the switching means switches to the input color image signal, and if a positive decision is made. , 3 from the coordinate reverse transformation means
The color separation signals are switched by the switching means.

In the present invention, the color-converted image is temporarily displayed by the display means.

[0016]

Embodiments of the present invention will now be described in detail with reference to the drawings.

<First Embodiment> FIG. 1 shows a first embodiment of the present invention. This is an example of a digital color copying machine, and the appearance of the operation unit / display unit is shown in FIG.

In FIG. 2, 201 is an image display unit, 20
Reference numeral 2 is a copy start key, 203 is a numeric keypad, 204 is a function key, and 205 is a control key.

When the original is set and designated by the color conversion mode function key 204, the original is scanned and the original image is displayed on the image display unit 201. If the color before conversion or the color after conversion is designated in the image or in the color sample (not shown), the image converted according to the designation is displayed, and when the start key 202 is pressed, the displayed image is printed out. It

When looking at the displayed image and adjusting the range of color conversion or the designated color, the function key 20 is used.
Specify the range adjustment or the specified color adjustment with 4. afterwards,
Adjustment is performed with the ten keys 203 or the control keys 205. The adjusted image is displayed again on the image display unit 201, and then the above process is repeated to obtain an output image.

In FIG. 1, reference numeral 101 denotes an image reading unit which reads a document image and outputs corresponding three-color digital signals of red (R), green (G), and blue (B) (8 bits each). Reference numeral 102 denotes a shading correction circuit for correcting the flutter of the reading unit and the optical system, and 103.
Is an input masking circuit for obtaining a standard three-color signal (NTSC-RGB in this example) from the three-color image signal obtained from the sensor. Reference numeral 104 denotes a color conversion unit, and 105 denotes L for converting the R, G, B light amount signals into cyan (C), magenta (M), and yellow (Y) toner density signals.
It is an OG table. Reference numeral 106 denotes each color recording signal C, M, Y from the density signals C, M, Y in consideration of the spectral characteristics of the toner.
It is a UCR / output masking circuit that generates Bk (black) in a frame sequential manner. The spatial filter 107 performs edge enhancement, smoothing, etc. as necessary, and outputs the final recording signal to a printer (not shown).

The color conversion unit 104 performs coordinate conversion of the RGB three color signals to obtain hue (H, hue (0 to 360 °)), saturation (S, saturation (0 to 255)), and lightness (I, intensity (0). To 255)), a coordinate conversion (RGB-HSI conversion) unit 108 for generating three signals;
Look-up tables (LUTs) 109 to 111 for converting H, S, and I signals into H1, S1, and I1 different from the original by a conversion table set in advance;
An inverse coordinate conversion (HSI-RGB conversion) unit 112 that returns 1, S1 and I1 to signals on the original RGB coordinate system.

As described above, when the coordinates of the color before the conversion and the coordinates of the color after the conversion are designated and the start key is pressed, the R, G, B three color signals of the designated two coordinates are pre-scanned and the image reading unit is operated. Read from 101. From this and the coordinates, the color before conversion and the color after conversion are extracted, and the CPU (not shown)
Then, the contents of the lookup tables 109 to 111 are calculated and written. After that, when forming an image by main scanning,
The converted image is output through this LUT.

FIG. 3 shows an example of the contents of the LUT 109 shown in FIG. In this example, only the hue H is converted from green (120 °) to red (0 °), and the saturation S and the brightness I are through.

The hue H before conversion is close to 120 ° (60 °
~ 180 °), the closer to 120 ° the converted color (0
°) is converted to a hue close to, and near the boundary is converted closer to the color before conversion. Therefore, it is possible to obtain a color-converted image that is natural in appearance without being unnaturally discontinuous in the color boundary portion.

The example of FIG. 3 is an example, and the contents of the LUT are not limited to this. Further, although the example in which the conversion operation result is written in the LUT in advance has been described in the present embodiment, it is also possible to perform the conversion by the operation using the operation circuit or the operation processor.

<Second Embodiment> FIG. 4 is a block diagram showing the arrangement of the color conversion section 104 in the second embodiment.

In the first embodiment, the hue H, the saturation S, and the lightness I are independently converted by the LUTs 109 to 111.
It is also possible to correspond by using an LUT in which two or three of the three coordinates are correlated. In this case, in order to reduce the number of address bits of the LUT, the main signal among the three signals, for example, the number of H bits in the H conversion LUT is preserved, and the other is, for example, the bits of the S and I signals in the H conversion LUT. The number can be reduced and input.

In this embodiment, the main signal 8 bits and the other signal 3 bits, 14 bits in total, are used as the HLUT 401 and the SLUT 4.
02, the LUT input signal of the ILUT 403, and the converted signals are output in 8 bits.

By thus correlating and converting the three signals, for example, when it is desired to convert the flesh color to reddish, the degree of conversion is increased in a part of the main hue of the flesh color having a slightly low saturation, It is possible to perform color conversion with higher saturation, such as reducing the area close to orange (higher saturation).
Although only the high-order bits are used here to reduce the number of bits of signals other than the main signal, other than the main signal, a binary signal is made by a comparator and the LU signal is 10 bits in total.
Various methods such as inputting into T are possible.

<Third Embodiment> In the first embodiment, when different processing is performed for each area, the processing can be easily performed by inputting the area signal to the address of the LUT.

Here, when the coordinate conversion unit 108 and the coordinate inverse conversion unit 112 are configured by hardware, there is a possibility that an image may be deteriorated due to an error due to calculation or a bit loss. Therefore, when the input and output of each LUT are equal (that is, when color conversion is not performed), R, G, and B are directly output without passing through the coordinate conversion unit 108, thereby causing deterioration of the image due to coordinate conversion. It can be reduced.

FIG. 5 shows the color conversion section 10 in the third embodiment.
4 shows the configuration of No. 4. In FIG. 5, 501 is a signal MODE indicating a conversion mode, and 502 to 505 are comparators (CM) that output 1 when two inputs are equal and 0 otherwise.
P). Reference numeral 506 is an AND gate, 507 is an OR gate, and 508 is a selector.

The mode signal MODE is controlled by a CPU (not shown), and the LUT corresponding to each MODE value in advance.
Is written. Therefore, the mode can be easily switched by changing the MODE signal for each area.

On the other hand, in the comparators 502-504,
Always compare the input and output signals of the LUT and output "1" if they are equal, and "0" if they are different.
Is output. These three signals pass through the AND gate 506,
When all three signals have not changed, that is, when color conversion is not performed, the AND gate "1" is output.

The comparator 505 has a mode signal MOD.
It is monitored whether E is a predetermined value (a value indicating the through mode), and when the through mode is designated, the OR gate 507 forcibly outputs "1".

The selector 508 includes RGB before one conversion,
RGB that has undergone conversion-reverse conversion is input to the other, and the signal before conversion (through signal) is output when the above-mentioned OR output becomes "1", and the converted signal when it is "0". Is output.

In this way, at the same time as switching the area for which color conversion is performed, the area for which color conversion is not performed, or the type of conversion for each area, it is possible to obtain output without degrading pixels or areas that are not converted.

[0039]

As described above, according to the present invention,
An input color image signal composed of color separation signals of three colors is converted into a tint multivalued signal represented by hue, saturation, and lightness, and the tint multivalued signal obtained by the conversion is designated in advance. Another color tone multi-valued signal is converted, and the color tone multi-valued signal obtained by the conversion is returned to the color separation signal of three colors, so that the transition is inconspicuous and a good color conversion image is obtained. be able to.

Further, according to the present invention, it is determined whether or not the tint has changed, and if a negative determination is made, the input color image signal is switched to, and if an affirmative determination is made, the coordinate reverse conversion means outputs. Since the color separation signals are switched to three colors, coordinate conversion can be performed without unnecessarily deteriorating the image.

[Brief description of drawings]

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

FIG. 2 is an external view showing the external appearance of the operation / display unit of the digital color copying machine of the first embodiment.

FIG. 3 is a diagram showing an example of contents of an LUT 109.

FIG. 4 is a block diagram illustrating a configuration of a color conversion unit 104 according to a second embodiment.

FIG. 5 is a block diagram showing a configuration of a color conversion unit 104 in a third embodiment.

FIG. 6 is a block diagram showing a conventional color image processing device.

[Explanation of symbols]

 101 image reading unit 102 shading correction circuit 103 input masking circuit 104 color conversion unit 105 LOG table 106 UCR / output masking circuit 107 spatial filter 201 image display unit 202 copy start key 203 numeric keypad 204 function key 205 control keys 502 to 505 comparator 506 AND Gate 507 OR gate 508 Selector

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H04N 1/46 Z

Claims (6)

[Claims] 1. A coordinate conversion means for converting an input color image signal composed of color separation signals of three colors into a multi-valued tint signal represented by hue, saturation and lightness, and by the coordinate conversion means. The tint multivalued signal obtained by converting the tint multivalued signal to another tint multivalued signal designated in advance, and the tint multivalued signal obtained by the tint conversion means are converted into 3 A color image processing apparatus, comprising: a coordinate reverse conversion means for returning a color separation signal of a color. 2. The color image processing apparatus according to claim 1, wherein the tint conversion unit is a table reference unit. 3. The color image processing apparatus according to claim 1, wherein the tint conversion unit is a calculation unit. 4. The area specifying means according to claim 1, further comprising area specifying means for specifying a specific area, wherein the tint converting means switches a conversion type for each area specified by the area specifying means. Color image processing device. 5. The determination unit according to claim 1, wherein the tint conversion unit determines whether the tint has changed, and when the determination unit makes a negative determination, the input color image signal is switched to and affirmative. A color image processing apparatus comprising: switching means for switching to color separation signals of three colors from the coordinate reverse conversion means when determined. 6. The color image processing apparatus according to claim 1, further comprising display means for temporarily displaying an image whose color is converted.