JPH084320B2 - Color image forming apparatus - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a color image forming apparatus, and more particularly to a color image forming apparatus capable of halftone full color reproduction.

<Prior Art> The color that can be reproduced by a full-color printer is approximately 260,000 colors if each 6 bits, that is, 64 gradations, can be reproduced by using three primary colors of cyan (C), magenta (M) and yellow (Y). If the input signal is for a full-color natural image, it is desirable to select a color from the 260,000 colors as close as possible to the original image and print it.

However, when the input target is a color graphic signal of a commercially available personal computer, the number of colors for expressing characters and graphics is 3 bits for each of red (R), green (G) and blue (B). Most of them reproduce 8 colors, and some of them are 16-color type with 2 bits of green. In any case, the number of colors that can be reproduced by a full-color printer is extremely small.

On the display, the color reproduction is performed with an additive color mixture based on black, whereas the print is performed with a subtractive color mixture based on white. Therefore, a dark background color is selected on the display side, while a bright color is preferable on the printed matter. In addition, there is a problem that bright colors, such as yellow, which are visible on the display are difficult to recognize on the print paper.

<Purpose> Therefore, in the present invention, an appropriate color conversion circuit is provided for a graphic color signal of a computer display or the like, and it is possible to print on a print paper surface in another preferable color, and a character or a figure can be printed. An object of the present invention is to provide a color image forming apparatus that makes it easy to see.

<Embodiment> First, the entire block diagram of FIG. 1 will be described along the flow of color signals. There are two input systems, one is a full color halftone analog signal, and the other is a graphic color digital signal. A / for full color
The D converter 10 converts it to a 6-bit digital signal, and the image processing circuit 20 performs gradation correction and masking processing to reproduce colors faithfully to the input, and converts it to a 6-bit C, M, Y signal. Then, 40C, 40M, 40Y are driven through the head driver 30.

Next, in the case of graphic color, since the input is given as a digital signal, it is directly input to the color conversion circuit 50,
Then, it is converted into color signals of 6 bits each for C, M, and Y, and is printed by the same processing as full color printing. Also,
The system controller 60 controls the motors CM and LF that control the overall signals and SW input, LED display, carriage movement of the head, and line feed movement.

 Next, FIG. 2 shows an actual configuration example of the color conversion circuit 50.

The color conversion circuit 50 can be realized by a table conversion ROM having 3 bits as an input and 3 colors × 6 bits = 18 bits as an output.

 FIG. 3 shows the specific contents of the table.

In this example, when R = G = B = 0, the input color is black, but Y, M, and C are reproduced in very light colors, and conversely R = G =
When B = 1, the input color is white, but this is printed with the maximum density of Y, M, and C. Input colors R, G, B, C, and M are printed with the same hue and maximum density. Further, when the input color of R = G = 1, B = 0 is yellow, it is difficult to see only with the yellow ink, so a little magenta is added to make the color yellow to make it easier to see.

In this way, the color conversion circuit 50 obtains a predetermined preferable color recording signal.

In the above implementation, the color conversion circuit was realized by ROM, but if the contents of the conversion table can be changed externally by using RAM, various color conversions can be performed, and the color conversion of the false color can be performed. Even if the number of colors increases, you can deal with it by increasing the size of the table accordingly, and even if you do not have a conversion table for all colors, you can obtain the same effect by converting only some specific colors. .

<Effects> As described above, in the full-color printer, when the input signal is a few colors of graphics color (or forth color), the characters and figures are recognized by printing using the color conversion table. It is possible to make it easier, for example, to remove useless background color.

[Brief description of drawings]

FIG. 1 is an image processing block diagram of this embodiment, FIG. 2 is a color conversion circuit diagram, and FIG. 3 is a diagram showing the contents of a color conversion ROM.

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Claims (1)

[Claims] 1. A color image forming apparatus for reproducing a color image by a halftone color image signal and a graphic color image signal, wherein a halftone process is performed on the halftone color image signal to faithfully reproduce the input signal. An image processing circuit for obtaining a recording signal and a color conversion circuit for performing arbitrary color conversion on a specific color of the graphic color image signal to obtain a color recording signal corresponding to a predetermined preferable color. Color image forming apparatus.