JPH1056578A - Color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To embed a large quantity of additional information in a color image without visually being an obstruction and also without deteriorating image quality. SOLUTION: Basically, each basic structural color which comprises a color image that is inputted from an image input means is drawn according to the density of color pixels of basic structural colors which should by outputted by a largest driving system gathering of parallel lines screen which changed line width of the basic structural colors. When information which should be added to the color image is inputted from a triangular wave selective signal generator 25 and when the system 27 draws, a triangular wave oscillator 23, the generator 25 and a selected-circuit 24 change the drawing position of output color pixels of the basic structural colors which constitute the color image in the direction of line which of the gathering of parallel lines screen, and a comparactor 26 uses the gathering of parallel lines screen at the changes position and makes the system 27 draw color pixels.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a digital copying machine,
A color image forming apparatus that forms a color image with pixels, such as a digital printer, an ink jet printer, a printing machine, and the like, and in particular, a color that embeds information other than the visually perceived color image in the color image so as not to be obstructive The present invention relates to an image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, in the field of image formation,
2. Description of the Related Art For the purpose of increasing the amount of information or concealment from a third party, information other than the image, such as text or characters, has been added and mixed into the image.

For example, Japanese Patent Application Laid-Open No. Hei 7-123244 discloses that, when a color image is formed, information different from the color image such as text information is used so that the total of the three primary color components of the color image does not change. There is disclosed an invention in which any one of the color difference and the saturation is changed and embedded. The present invention embeds other information in a color image so as not to be obstructive, utilizing the fact that a change in color difference or saturation at a high frequency is hardly recognized by a human.

However, according to the present invention, in order to reliably read the embedded information with a scanner or the like, a change in color difference or saturation must be largely changed. There was a drawback that it would be done.

Japanese Patent Application Laid-Open No. 4-294682 discloses an invention in which a yellow toner is used to embed a device number, a user identifier, and the like in a color image in a specific pattern that is difficult for human eyes to identify. ing. The present invention embeds other information in a color image without hindrance by utilizing the fact that human eyes have low discrimination ability with respect to a specific pattern drawn with yellow toner. However, according to the present invention, since an extra signal is added to a color image, there is a disadvantage that the added signal becomes noise and deteriorates the image quality of the original color image.

[0006] Japanese Patent Application Laid-Open No. 4-334266 discloses "gl
The invention discloses a technique for embedding digital data in a halftone image using pictograms such as "yphs". However, in the present invention, it is necessary to provide a halftone image area in a document image, and the pictogram itself must be provided. Since it is larger than a pixel, there is a disadvantage that the amount of additional information that can be embedded is small.

Japanese Patent Application Laid-Open No. 4-131111 discloses two different K (black) amounts (UCR amounts) for Y (yellow), M (magenta), and C (cyan) color image data. There is disclosed an invention in which states are created, "0" or "1" is assigned to these states, and ID information is added to the image. However, in the present invention, Y,
It is necessary to include all the components of M and C. For example, there is a disadvantage in that ID information cannot be added to an image that includes Y and C but does not include M.

Japanese Patent Application Laid-Open No. 63-214067 discloses that, when an image is represented by using a dither method, the arrangement of elements in a dither matrix is determined based on information to be added, and another information is included in the image. Are disclosed. In Japanese Patent Application Laid-Open No. 2-266390, the output (1,0) and (0,
There is disclosed an invention in which “0” and “1” are assigned to 1) and other information is embedded in an image.

However, in these inventions,
There is a drawback that the method cannot be applied unless the image forming apparatus uses a dither matrix as the gradation expression. In the case where the information is embedded in an electronic image, the position of the dither matrix can be specified. Therefore, it is easy to read out the embedded information later. However, it is almost impossible to specify the position or pattern of each of the two-dimensionally arranged dither matrices from an image read by an image reading device, and it has been difficult to read embedded information.

[0010]

As described above, there have conventionally been proposed various inventions in which information other than the image is embedded and added to the image. However, the addition of information deteriorates the image quality of the image. Or, there have been various problems that the amount of information that can be added is small, information cannot be added in principle depending on the image, or it is difficult to read embedded information.

The present invention has been made in view of the above-mentioned conventional circumstances, and is a color image forming apparatus capable of embedding a large amount of additional information in a color image without visually obstructing and deteriorating the image quality. The purpose is to provide.

[0012]

SUMMARY OF THE INVENTION The present invention is characterized by focusing on output color pixels of each basic constituent color in output pixels constituting an output color image. The additional information is embedded in the output color image by changing the drawing position of the output color pixel of each of the basic constituent colors according to the code.

That is, in the color image forming apparatus according to the first aspect of the present invention, basically, each basic constituent color constituting the color image input from the image input means is output by the image drawing means. The drawing is performed using a line screen that changes the line width of the basic constituent color according to the density of the output color pixel of the constituent color. When the information to be added to the color image is input from the information input unit, the position change unit inputs the drawing position of the output color pixel of each basic constituent color by the information input unit when drawing by the image drawing unit. According to the information, it changes within the screen width in the line width direction of the line screen, and the control means uses the line screen at the position changed by the position changing means, and the output color pixels of each basic constituent color by the image drawing means using the line screen. Is drawn.

In the color image forming apparatus according to the second aspect of the present invention, basically, each basic constituent color constituting the color image input from the image input means is output by the image drawing means. The drawing is performed using a dot screen that changes the size of the output color pixel of the basic constituent color according to the density of the color pixel of the constituent color. When the information to be added to the color image is input from the information input unit, the position change unit inputs the drawing position of the output color pixel of each basic constituent color by the information input unit when drawing by the image drawing unit. The information is changed in the cell according to the information, and the control means causes the image drawing means to draw the output color pixels of each basic constituent color at the position changed by the position changing means using the dot screen.

Further, in the color image forming apparatus according to the third aspect of the present invention, the basic configuration of the output color pixel which is rendered as the same output pixel by the image rendering means by the input amount of the additional information input from the information input means. Change according to the type of color.

The above-mentioned basic constituent colors are colors that can express more colors by using a plurality of basic constituent colors. For example, when printing on a medium such as paper, Usually means Y (yellow), M (magenta), C (cyan), and K (black).
It is not limited to Y, M, C, K.

The above-mentioned output pixels are formed by output color pixels of one or more basic constituent colors, and are the minimum unit that can be rendered by an output device (printer, copier, facsimile, plate generator in printing, etc.). Yes, and its minimum unit size, form, and position are variable. The width of the line screen refers to the maximum width of an output pixel, for example, 200 lines (200 lines per 25.4 mm).
Is 0.127 mm in the case of the line screen. The above-mentioned cell refers to a unit area constituting the dot screen, for example, a minimum rectangular area indicated by a dotted line as shown in FIG.

According to the image forming apparatus of the present invention, a large amount of additional information can be embedded without deteriorating the image quality of a color image by utilizing the properties of a line screen or a dot screen.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of a color image forming process according to the present invention. The color image forming apparatus is roughly divided into a pixel generation process 1 and a pixel output process 2
When a color image that is visually perceived and additional information data different from the color image are input, the present invention provides a pixel generation step 1 according to the additional information data and the color image data. The present invention is characterized in that the arrangement of output color pixels of each basic constituent color is changed to generate output color pixels of each basic constituent color of output pixels forming an output color image. The pixel output step 2 may be performed by any means capable of outputting pixels, such as electrophotography and ink jet.

As a first embodiment of the present invention, a main portion of an electrophotographic color laser printer for generating an image using a line screen will be described with reference to FIG. This laser printer includes a drawing color switch 21, a D / A converter 22, a triangular wave oscillator 23, a selection circuit 24, a triangular wave selection signal generator 25, a comparator 26, a laser drive system 27, and an adder 28. I have. The input color images are Y (yellow), M (magenta), C (cyan), and K (black).
It consists of two basic constituent colors.

The drawing color switch 21 receives the input Y, M,
An image signal of the basic constituent color specified by the drawing color switching signal is selected from the basic constituent colors of C and K, and input to the D / A converter 22 via the adder 28. In the drawing color switching signal, for example, first, Y is specified, the drawing processing of the output color pixel of Y is performed, and then the drawing processing of the output color pixel is sequentially specified as M, C, K. . Therefore,
The output pixels are formed by drawing the four output color pixels of Y, M, C, and K.

The D / A converter 22 converts the image signal (digital density information) input from the drawing color switch 21 into an analog voltage and outputs this to one input terminal of a comparator 26. The triangular wave oscillator 23 generates a triangular wave for changing the drawing position of the output color pixel in the width direction of the line screen. Specifically, four types of triangular waves 29 having different vertices as shown in FIG. 30, 31, and 32 are generated.
Therefore, four different drawing positions are determined by the triangular wave. Note that the width of one unit of the triangular waves 29, 30, 31, and 32 corresponds to one unit of the width of the line screen. The selection circuit 24 selects one of the generated triangular waves 29, 30, 31, and 32 and outputs this to the other input terminal of the comparator 26.

The triangular wave selection signal generator 25 converts the basic constituent colors to be drawn specified by the drawing color switching signal, the input color image data (Y, M, C, K), and the information data to be added to the color image. A selection signal for selecting a triangular wave based on the selected signal is transmitted, and the selection processing of the selection circuit 24 is controlled.

That is, the triangular wave selection signal generator 25
First, the number of basic constituent colors of output pixels constituting a color image to be drawn is checked, and the number of bits representing the data amount of information to be added to the pixel is determined. For example, in the case where the output color pixels of the output pixels have four drawing positions, and the color image data is composed of the four basic constituent colors of YMCK, the drawing positions of the output color pixels for each of the YMCKs are separately set. Up to 2
Since four types of arrangement are possible, additional information data
Bits (16 types of data) are determined. Similarly, when the color image data is composed of three basic constituent colors, the additional information data is determined to be 4 bits (16 types), and when the color image data is composed of two basic constituent colors, When the color image data is composed of one basic constituent color, the additional information data is determined to be 2 bits (8 types).
Street).

Next, the additional information data for the determined number of bits is received, and the received additional information is used by using a conversion table indicating the correspondence between the additional information data and the drawing position of the output color pixel of each basic constituent color. A drawing position of an output color pixel of each basic constituent color representing data is obtained.

The conversion table showing the correspondence between the additional information data (4 bits) and the drawing positions of the output color pixels of the four basic constituent colors is, for example, the one shown in FIG. As a conversion table indicating the correspondence between the information data (4 bits) and the drawing positions of the output color pixels of the three basic constituent colors, for example, the conversion table shown in FIG. 3B is used, and the additional information data (3 bits) For example, the conversion table shown in FIG. 4A represents the correspondence between the drawing positions of the output color pixels of the two basic constituent colors.
FIG. 4B shows a conversion table representing the correspondence between the additional information data (2 bits) and the drawing position of an output color pixel of one basic constituent color.

A selection signal for detecting a drawing position of a basic constituent color of a drawing target specified by a drawing color switching signal based on the obtained drawing position, and selecting a triangular wave for drawing an output color pixel at the drawing position. And controls the selection circuit 24. Further, the triangular wave selection signal generator 25 outputs an instruction to correct the image data of the basic constituent color to be drawn by the adder 28.
Output to

The comparator 26 compares the analog voltage of the basic constituent color to be drawn with the level of a triangular wave (analog voltage).
When the level of the triangular wave is higher than the analog voltage of the input image, "H" (that is, the laser is turned on) is output, and when it is lower, "L" (that is, the laser is turned off) is output. Therefore, when the triangular wave 29 is selected, the “H” level is input to the laser driving system 27 at the latest timing, and when the triangular wave 32 is selected, the “H” level is input to the laser driving system 27 at the earliest timing. Is done.

The laser drive system 27 is a means for drawing an output color pixel using a line screen.
In accordance with the instruction, the image is drawn while scanning the output color pixels on the recording medium. Therefore, when the triangular wave 29 is selected, the output color pixels are drawn at the rearmost position in the main scanning direction within the line screen width, and when the triangular wave 32 is selected, the output color pixels are drawn within the line screen width. It is drawn at the forefront in the scanning direction.

The adder 28 generates a slight color difference from the conventional color image which is generated because the overlapping manner of the color pixels of the respective basic constituent colors of the output pixels constituting the color image output by the printer differs from the conventional one. Is a device for adding correction data for correcting the difference between the color pixels. When receiving a correction instruction from the triangular wave selection signal generator 25,
Correction data for correcting to the same color as in the related art is obtained from a lookup table, and the correction data is added to the image signal input from the drawing color switch 21 to the D / A converter 22.

According to the electrophotographic laser printer having the above-described configuration, the correction signal is added to the image signal of the basic constituent color selected by the drawing color switch 21 by the adder 28, and the analog signal is added by the D / A converter 22. The voltage is converted into a voltage and input to the comparator 26. Further, any one of the triangular waves 29, 30, 31, and 32 generated by the triangular wave oscillator 23 is selected by the selection circuit 24 in accordance with the basic constituent color to be drawn, color image data, and additional information data, and input to the comparator 26. You. The comparator 26 controls the laser drive system 27 at a timing based on the shape of the selected triangular wave to draw an output color pixel at a position displaced in the width direction within the width of the line screen.

The manner in which additional information is embedded in pixels constituting a color image containing Y, M, C, and K with a density of 25% by the above-described electrophotographic laser printer will be described with reference to FIG. In addition, since the density of each basic constituent color is 25%, the width of the output color pixel of each basic constituent color of the output pixels in the line screen is all 1 / screen width.
It is 4. In the output pixel of the line 71, the additional information data “0000” indicates the position of the output color pixel of the basic constituent color as Y.
Embedded by drawing as MCK,
For the pixels of the line 72, the additional information “0110” is assigned to the color pixel of the basic constituent color by the position of the color pixel of the basic constituent color by M.
It is embedded by drawing as YCK.
Note that the correspondence between the additional information data and the drawing positions of the color pixels is based on the conversion table shown in FIG.

The process of embedding the additional information data is as follows:
In the example shown in FIG. 5, it can be controlled by a control signal input to the triangular wave selection signal generator 25. In the example shown in FIG. 5, the information is added to every other line pixel in the main scanning direction so that information can be easily read from the output color image. The information data is embedded, and the sub-scanning direction is also spaced apart, for example, every other row. All the color pixels of the line portion where the additional information data is not embedded are drawn by the triangular wave 31.

Here, in the conventional image forming apparatus, since there is only one kind of triangular wave, all the YMCK pixels in the line screen are drawn and overlapped at the same position as shown in FIG. As can be seen by comparing FIG. 6 and FIG. 6, the ratio of the color pixels of each of the basic constituent colors in the line screen is the same, and a large amount of additional information can be embedded without deteriorating the image quality of the color image. Can be. Further, the addition of the correction data by the adder 28 can eliminate a slight color difference from a conventional color image. Further, by reducing the number of pixels in which the additional information is embedded, it is possible to effectively prevent deterioration of the color image.

In the example shown in FIG. 5, the explanation has been made using a color image in which all YMCKs have a density of 25%. However, in actual color images, the YMCK density often differs. The drawing situation of the color pixels when the densities of YMCK are different will be described with reference to FIG. FIG. 7 is a diagram when the basic constituent colors to be drawn drawn on the paper 99 are viewed from the side.
Position 93 and position 94 are respectively the triangular wave 3 shown in FIG.
The positions correspond to the positions of the vertices of 2, 31, 30, and 29, and the position 91
And 94 correspond to the width of the line.

In this example, the basic constituent colors 95 and 96, and the basic constituent colors 96 and 97 overlap each other. However, in this case, since the left end of the output color pixel of the basic constituent color 95 is at the position 91, the triangular wave 32
It can be understood that the drawing position is drawn by the triangular wave 31 because the 1/3 portion from the left end of the output color pixel of the basic constituent color 96 is located at the position 92. Since a 2/3 portion from the left end of the output color pixel of the color 97 is located at the position 93, it is known that the drawing position is drawn by the triangular wave 30, and the right end of the output color pixel of the basic constituent color 98 is located at the position 94.
, It can be seen that it is at the drawing position drawn by the triangular wave 29. Therefore, it can be seen that the drawing positions of the output color pixels are the basic constituent colors 95, 96, 97, and 98. As described above, the drawing position of each basic constituent color can be specified, and the embedded information can be read without any trouble.

[0037] Although remain embodiments described above there are cases where fault situation occurs, for which, because it is possible to grasp in advance what it like any trouble happens when, bug There is no problem if the countermeasures in case of occurrence are taken. For example, when K is included in the basic constituent colors, if the density of K is about 33% or more, there is a situation where it is impossible to specify the drawing position of another basic constituent color.
Although this is not a common situation considering that it is used for UCR (Under Color Removal) processing, the triangular wave selection signal generator 25 needs to be added when the concentration of K is higher than a certain value. Control may be performed so as not to embed information, or it may be configured to embed 2-bit information only in K1 color.

When the density of a certain basic constituent color among the basic constituent colors Y, M and C is 100%, the width of the color pixel coincides with the width of the line. In this case, the triangular wave selection signal generator 25 may be configured to embed additional information with other basic constituent colors except for the basic constituent color having a density of 100%. For example, Y: 20%, M: 100%, C: 30
%, K: 0%, the triangle wave selection signal generator 2
5 may be configured to embed information in two colors of Y and C.

To read the additional information embedded in the color image as described above, a system as shown in FIG. 10 is used. First, a color image is read from a document by the color image reading apparatus 101, and the color image (RG
B), after performing appropriate image processing such as shading correction by the image processing means 102, conversion from RGB to YMC by the conversion means 103, and YM
The drawing position of each output color pixel of C is detected.
Next, the embedded information restoring means 105 restores the information embedded in the color image according to the conversion table, and displays the information on the display by the display / processing means 106, or
A predetermined process is performed according to the additional information. The color image subjected to the image processing is displayed on the display by the image display means 107.

Here, usually, when forming an image such as a graphic or a photograph, the number of lines per line is 100.
Wire (100 wires per 25.4 mm) or 200 wires (2
(200 lines per 5.4 mm)
dots / 25.4mm or 1200dots / 2
With the color image reading apparatus 101 having a resolution of 5.4 mm, the arrangement order of YMCK color pixels can be specified, and the embedded information can be read without any trouble.

In this embodiment, if the drawing position of the color pixel is changed several lines continuously, the pixel 76 in FIG.
Can be lengthened in the sub-scanning direction. In this way, even if the color image read by the color image reading apparatus 101 has a certain degree of skew (inclination), additional information embedded in one scan in the main scanning direction can be extracted. Since it is not necessary to process a two-dimensional image, it is possible to extract additional information at a very high speed.

Next, an electrophotographic color laser printer for generating an image using a dot screen according to a second embodiment of the present invention will be described. The main part of the electrophotographic laser printer according to the second embodiment is the same as that of the first embodiment shown in FIG. 2, and a duplicate description will be omitted.

In the laser printer according to the second embodiment,
As shown in FIG. 9, the YMCK data of the input color image has a waveform 111 which is alternately switched at a density "0" and a certain density value. When it is “20”, the waveform 111 alternately switches between the density “0” and the density “40” so that the average density becomes “20”.

In this laser printer, the selection circuit 24
Assuming that the laser drive system 27 is driven at a period interval twice as long as the triangular wave selected by the above to draw color pixels, and the information to be added is the same as the information shown in FIG. 5 of the first embodiment, FIG. As shown in (1), the drawing position of the output color pixel of each basic constituent color is changed and embedded in the line indicated by the broken arrow. In the second embodiment, the additional information is embedded at an interval of one line in the sub-scanning direction, and the cells in which the additional information is embedded are arranged in a staggered manner. As described above, by changing the drawing position of each basic constituent color, a large amount of information can be embedded in a color image without any trouble.

In the second embodiment, as shown in FIG. 11, the color pixels of one pixel are expressed by two lines, and the arrangement order of the color pixels of each basic constituent color is changed. Information can also be embedded.

In the first and second embodiments described above, four types of triangular waves are provided, but the number of types of triangular waves is arbitrary. Information can be embedded in the pixel.

In the first and second embodiments, the additional information is embedded in every other line in the sub-scanning direction, so that the additional information can be easily read out and not obstructed in the color image. However, the additional information may be embedded in all the pixels of the drawing unit line in the sub-scanning direction, and the pixel in which the additional information is embedded can be arbitrarily determined.

In the laser printers described in the first and second embodiments, the addition of the adder 28 allows the color image of the conventional color image and the color image output by the present invention to have a slight color difference. Although the difference is eliminated, much information can be added to the color image without deteriorating the color image without the adder 28.

In the first and second embodiments described above, the input amount of the additional information is changed according to the basic constituent colors of the color pixels constituting the pixels on which the triangular wave selection signal generator 25 is drawn. However, when a color image composed of a certain basic constituent color is to be input, the above-described configuration is not necessary. If a certain amount of additional information is input, the color image can be embedded without any trouble.

In the above-described first and second embodiments, an example has been described in which drawing is performed while scanning pixels. However, as in the case of manufacturing a printing plate, a color image is formed by pixels without performing scanning. The present invention can also be applied to a device for generating. That is, the present invention can be applied to all image forming apparatuses that form pixels, such as digital copiers, digital printers, inkjet printers, printing machines, and the like.

[0051]

As described above, according to the color image forming apparatus of the present invention, when forming color images, the arrangement positions of the output color pixels of the basic constituent colors constituting these color images are added. Since the information is changed according to the information, a large amount of information can be embedded without obstruction without deteriorating the image quality of the color image. According to the color image forming apparatus of the present invention, the input amount of the additional information to be input is changed according to the type of the basic constituent color of the output color pixel drawn as the same output pixel. Information can be added to a color image regardless of the basic constituent colors of the image.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating a color image forming apparatus to which the present invention is applied.

FIG. 2 is a configuration diagram illustrating a main part of an electrophotographic laser printer according to an embodiment of the present invention.

FIG. 3 is a diagram illustrating a first example of correspondence between pixel arrangement of basic constituent colors and additional information in the first embodiment.

FIG. 4 is a diagram illustrating a second example of correspondence between pixel arrangement of basic constituent colors and additional information in the first embodiment.

FIG. 5 is a diagram showing a drawing example of a line screen in the first embodiment.

FIG. 6 is a diagram showing a conventional example of drawing a line screen.

FIG. 7 is a diagram illustrating a cross section of a drawing example of a line screen in the first embodiment.

FIG. 8 is a schematic configuration diagram showing an example of a system for extracting additional information embedded in a color image.

FIG. 9 is a diagram showing an example of color image data in a second embodiment.

FIG. 10 is a diagram illustrating a drawing example of a dot screen in the second embodiment.

FIG. 11 is a diagram illustrating another drawing example of the dot screen in the second embodiment.

[Explanation of symbols]

21: drawing color switch, 22: D / A converter, 23: triangular wave oscillator, 24: selection circuit, 25: triangular wave selection signal generator, 26 ...
.Comparator, 27 ... Laser drive system, 28 ...
・ Adder,

Claims (3)

[Claims] An image input unit for inputting a color image composed of a plurality of basic constituent colors; an information input unit for inputting information to be added to the color image; Image drawing means for drawing output color pixels of each basic constituent color of output pixels constituting a color image to be output, using a line screen for changing the line width of the color, and a color image input by the image input means Is changed within the screen width in the line width direction of the line screen in accordance with the information input by the information input means, in accordance with the information input by the information input means. Control means for drawing an output color pixel by the image drawing means using a line screen at a position changed by the position changing means. A color image forming apparatus comprising: 2. An image input means for inputting a color image composed of a plurality of basic constituent colors; an information input means for inputting information to be added to the color image; An image drawing means for drawing output color pixels of respective basic constituent colors of output pixels forming a color image by using a dot screen for changing the size of a color output color pixel; and a color input by the image input means. Position changing means for changing the drawing position of the output color pixel of each basic constituent color when drawing an image by the image drawing means, in a cell of the dot screen, in accordance with the information input by the information input means; Control means for drawing an output color pixel by the image drawing means using a dot screen at the position changed by the position changing means. A color image forming apparatus. 3. The color image forming apparatus according to claim 1, wherein said information input means is adapted to correspond to a type of a basic constituent color of an output color pixel rendered as the same output pixel by an image rendering means. A color image forming apparatus for changing the amount of input data of information to be added.