JPH03181276A - Picture copying machine - Google Patents

Abstract

PURPOSE:To extract a black character area excellently by obtaining plural distribution quantities respectively, obtaining the probability of black character area from each distribution quantity and discriminating the black character area from the probability of black character area. CONSTITUTION:The machine is provided with 1st arithmetic means 2-4 obtaining plural distribution quantities with respect to picture information, a 2nd arithmetic means 2-5 obtaining the probability of black character area from each distribution quantity obtained by the 1st arithmetic means 2-4, a discrimination means 2-6 discriminating the black character area from the probability of black character area obtained by the 2nd arithmetic means 2-5 and a copying means 2-7 processing the picture based on the result of the discrimination means 2-6 and copying the picture. In this case, the plural distribution quantities are referred to as intermediate tone, black dot density, contrast and chromatic color. The probability of black character area is obtained from the plural distribution quantities and whether or not the area is the black character area is discriminated. Thus, an excellent picture is copied.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention performs image area separation on input image information,
The present invention relates to an image copying apparatus that processes and copies images based on the separation information.

[Prior Art] Conventionally, this type of device reads a document using an image sensor such as a COD, extracts a black character area from the A/D converted image information, and outputs an image based on the result. Copies are made using a laser beam printer (LBP) or the like. Image area separation technology for extracting black character areas is well known, especially for black and white originals.
Generally, a pixel matrix of about 3 x 3 pixels is extracted,
It is configured to determine whether it is a text or a photograph based on the difference in density values between the center pixel and its surrounding pixels.

In recent years, color copying machines are also using text.

There are products that attempt to separate photographic areas pixel by pixel, but
This is done pixel by pixel. For example, if an edge component is present in an achromatic color, it is generally determined that it is an edge part of a black character.

[Problem to be Solved by the Invention 1] However, in the conventional example described above, the judgment criteria are inevitably simplified due to the hardware configuration, and the judgment criteria are also binary, so there is a problem that it is easy to misjudge the extraction of black character areas. was there.

Then, by ANDing the binary information indicating that the area contains an edge component and the binary information indicating that it is an achromatic color,
Although it is determined that it is an edge area of black text, for example, the judgment can be made when the color is close to an achromatic color and there is a slight edge component, or even if the color is close to an achromatic color, it is a color that is close to white or close to black. This has the disadvantage that it is not reflected in the judgment, and as a result, it is easy to make a false judgment.

The present invention was made to solve the above problems, and
It is an object of the present invention to provide an image copying apparatus that can copy good images by determining the probability of a black text area from a plurality of distribution amounts and determining from these whether the area is a black text area.

[Means for Solving the Problems] In order to achieve the above object, an image copying apparatus of the present invention has the following configuration. That is, in an image copying apparatus that performs image area separation on input image information, processes the image based on the separated information, and copies the image, a first step that calculates a plurality of distribution amounts for the image information, respectively. a calculating means, a second calculating means for calculating a black character area probability from each distribution amount determined by the first calculating means, and determining a black character area from the black character area probability calculated by the second calculating means; and a copying means for processing and copying an image based on the result of the determining means.

Preferably, each of the plurality of distribution amounts is a distribution amount of a halftone, a black dot density, a contrast, and a chromatic color.

[Operation] In the above configuration, a plurality of distribution amounts are measured for image information, and a black character area probability is determined from each distribution amount. Then, a black character area is determined based on the obtained black character area probability, image processing is performed based on the result, and the image is copied.

[Embodiments] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First Embodiment> FIG. 1 is an external perspective view showing an image copying apparatus in an embodiment. In the figure, reference numeral 1-1 denotes a document reading section and an image processing section, which includes a line-shaped CCD that is an optical system light receiving element for scanning a document and various image processing sections to be described later.

Moreover, COD in Examples is R (red) and G (green).

3 consisting of various B (blue) optical filters
It is a line color image sensor. 1-2 is a digitizer which also serves as a pressure plate for pressing the original.

1-3 is the operation unit, which instructs to start reading the original;
Select the number of copies, select various image processing, etc. 2-4 is a printer that outputs binary data, and in this embodiment, a laser beam printer (LBP) is used.

Next, the configuration of the document reading section and image processing section 1-1 in the embodiment will be explained below with reference to the block diagram shown in FIG.

Reference numeral 2-1 denotes an original, which is placed below the original pressing plate 1-2 in FIG. 2-2 is an optical lens that forms an image of the original on the CCD. 2-3 is COD, R (red),
It is composed of three lines of COD with G (green) and B (blue) optical filters.

Here, COD, the number of light-receiving parts for one line, consists of the number of light-receiving parts for one line of the document table, for example, the entire X direction;
If the direction is 30cm and 16pe 1 reading, then 30
It is composed of x160=4800 or more light receiving sections. When scanning a document, the imaging lens 2-2
．． C0D2-3 is scanned in the X direction to read the original.

The CCD 2-3 converts the document information into analog electrical signals, and outputs the converted R, G, and B various signals to the analog signal processing section 2-4.

2-4 is an analog signal processing section, which performs sample & hold, dark level correction dynamic range control, etc. for each color, performs A/D conversion (analog-digital conversion), and input image processing section 2. Outputs R, G, and B signals to -5. 2-5 is an input image processing unit, which performs shading correction, which is correction of the light-receiving sensitivity of each light-receiving part of the CCD, for each of the input R, G, and B colors.For details, refer to the image processing unit 2-6, which will be described later. Output.

2-6 is an image processing unit, which performs image area separation for separating the black character area, which is the center of the embodiment, C (cyan), 9M (magenta), and 9M (magenta) corresponding to the color ink of the printer from the R, G, and B color information. A logarithmic conversion unit that converts to Y (yellow), a masking conversion unit that performs conversion according to the output color characteristics of the printer, C,
It is composed of an under color removal unit (UCR) that separates gray components from M and Y and replaces them with B and (black).

The C, M, Y, and Bx density information mentioned above is stored in the printer section 2-7.
and is copied onto paper by an output device. 2-8
is a control unit (CPU) that controls each of the above-mentioned processes, and 2
-9 is an operation unit corresponding to 1-3 shown in FIG.

Next, the black character area probability function, which is the gist of the present invention, will be explained with reference to FIGS. 3(a) to 3(d).

All functions shown in Figures 3(a) to (d) are plotted on the vertical axis (y
The axis) represents the probability of being in a black text area, and indicates that the probability increases as the value on the y-axis increases.

Further, the various distributions on the horizontal axis (y-axis) indicate the amount of distribution per unit area, and as the value on the y-axis increases, the amount of distribution increases. Below, each function will be explained in turn.

The diagram shown in FIG. 3(a) represents a function between the black dot density distribution and the black character area probability. Here, the black dot density represents the achromatic color data density above a certain density. In general, the black dot density is very high in monochrome photographic originals, and on the contrary, it takes a very small value in color photographic originals. On the other hand, although it varies depending on the type of character, the normal 2m
If m-square type is used as a standard, the probability will take a maximum value in a certain density distribution, and the relationship between the black dot density distribution and the black character area probability is expressed by the formula (2).

P+ =-(B IXI +a) ”・”
■However, the same can be said for the following functions, but the black character area probability cannot be determined uniquely from the black dot density distribution alone, and must be considered in combination with other functions.

Next, the diagram shown in FIG. 3(b) shows the relationship between contrast distribution and black area probability. The contrast distribution indicates the amount of edge components of luminance information within a certain area, and indicates that as the X-axis increases, the amount of edge components increases by a certain amount or more. In general, black text manuscripts have a certain edge component, depending on the type of characters, and for example, a picture expressed in tod has a larger amount of edge component. However, the main purpose of separating the black character area is to prevent characters that are originally black from being reproduced with color shift due to color shift in the reading system such as COD, color shift due to overlapping toner, etc. Therefore, for example, it is safe to judge that a collection of dots is a character. Therefore, the relationship between the contrast distribution and the black character area probability is expressed by the following equation.

Pt” Ctx+
...■ The diagram shown in FIG. 3(c) shows the chromatic color distribution and the probability of black character area. The chromatic color distribution indicates the amount of chromatic color per unit area, and the relationship between the chromatic color distribution and the black character area probability is set to the equation 0.

Ps = -L +-+ +1 ・"■However, this relationship only holds true for color originals. For example, in the case of a black-and-white photo original, the entire surface is achromatic, but since it is not text, this relationship holds true only for color originals. Get out of the relationship.

Next, the diagram shown in FIG. 3(d) shows the relationship between halftone distribution and black character area probability. Generally, there are almost no halftones in black text manuscripts, and the relationship between the two is expressed by the formula (■).

P4 = 1/M(+B...■ However, when the present invention is actually implemented in hardware, depending on the configuration, it may be considered that the relationship is expressed by the formula (■) as shown by the dotted line.

P4 = -M, x, +1 . . . Black character area probability p, determined by four types of functions greater than or equal to 0.
The existence probability P is obtained from p, , ps, p using the equation (2), and the type of manuscript is separated based on the value of P (according to the conditions of the equation 0).

P=Arashi (P+ +Px +Ps +P4)...
■When P≧%, black character area P≧%, other document areas ...0th order,
A first embodiment for performing the above-mentioned image area separation will be described below with reference to the circuit configuration block shown in FIG.

In the figure, R, G, and B of the input terminal indicate image information K (luminance), R (red), G (green), and B (blue), respectively, and the S output terminal indicates whether or not it is a black text area. This is binary information indicating whether the

4-1 and 4-2 are registers that store the upper and lower limit values of image information density for cutting out halftone data, and are set to arbitrary values by the CPU 2-8. 4-3
．． 4-4 is a comparison circuit, which compares the input value of K with the value of each register 4-1 and 4-2, and outputs the result to AN.
Output to D circuit 4-5. If the pixel is a halftone, it is "l", otherwise it is "O". 1-6 is a counter, which is cleared every certain pixel area, and the output from the AND circuit 4-5 is 1゛.

It is configured to count up only if the pixel is . Then, the count value counted up for a certain area is stored in the ROM4- for each certain area as the halftone distribution amount.
Sent to 18.

In the following, in this example, the distribution amount is calculated every 10 pixels, and for example, there are 4 halftone pixels in the first 10 pixels,
If it is 2 pixels out of the next 10 pixels, r4J, r2
The count value J is sequentially sent to the adder circuit 4-20. 4-7 is a MAX (maximum) and MIN (minimum) extraction circuit, which extracts the maximum color information and minimum color information for each input of R9G and B, and a detailed explanation will be given later. . 4-8 is a subtraction circuit, (MAX) (MIN
) is calculated. Ideally, the achromatic color is (MAX) - (M
IN)=O, but the boundary value between achromatic color and chromatic color is set in register 4-9 in consideration of error and margin. 1
-10 is a comparison circuit, which compares the subtraction result (B) from the subtraction circuit 4-8 and the value (A) of the register 4-9. A
<B output indicates that the subtracted value is less than a certain value and is a chromatic color. Further, A≧B output is below a certain value, indicating an achromatic color.

4-11 is a counter, which, like the counter 4-6 described above, has a function of counting the amount of chromatic color distribution for each fixed area. Further, 4-13 is an AND circuit which performs an AND operation between the binary information indicating the achromatic color from the above-mentioned comparison circuit 4-10 and the multi-value luminance information. In other words, AND circuit 4-13
The output is “O” if it is not achromatic (if it is chromatic),
If it is an achromatic color, it becomes luminance information. The boundary value of the black level is set in the register 4-12, and when it is determined that the color is achromatic and black based on the level of brightness information, the output of the comparison circuit 4-14 becomes "1". .

The counter 4-15 to which the result is input counts the amount of black dot distribution in each fixed area, similar to the counter 4-6 described above.

The edge extraction circuit 4-16 extracts edges of the luminance term,
If the edge amount is above a certain value, the circuit outputs "1", and the counter 4-17 similarly outputs the edge amount (
Contrast) Count the amount of distribution.

As explained above, in the first embodiment, the amount of halftone distribution,
The chromatic color distribution amount, the black dot distribution amount, and the contrast distribution amount are calculated respectively, and each member comprehensively determines whether or not the area is a black character area. In addition, in the graph shown in Figure 3 mentioned above, for simplicity, the relationship between each distribution amount and the black character area probability is expressed as a straight line except for the black dot distribution amount, but in general, the ideal linear relationship is In addition, it is common for various conditions to be weighted differently.

For example, the black character area probability is generally different when the chromatic color distribution amount is the minimum and when the halftone distribution amount is the minimum.

Therefore, each table ROM4-18゜4-24 in Fig.
．． 4-19.4-25 normalizes the relationship between various distribution amounts and black character area probability. In other words, when the addition circuit 4-20 performs addition, it is uniquely determined whether or not it is a black character area according to the black value. In addition, 4-21 is a % division circuit, which was provided separately to explain the above-mentioned formula (2), but it is actually a table ROM.
will absorb the horse circuit. And register 4-2
2 is a multi-value of 4-21, a boundary value of black character area probability information is set, and if the probability information is greater than or equal to the boundary value, the comparator circuit 4
Binary information indicating that it is a black character area from -23 is terminal S
is output to.

Next, the MAX and MIN extraction circuit 4-7 will be explained with reference to FIG.

In the figure, R, G, and B correspond to R, G, and B in FIG. 4 described above, respectively, and are (red) and (green).

(Blue). Further, the MAX output and the MIN output output the largest amount of color information and the smallest amount of color information among the three colors, respectively. 5-1.5-2.5-3 is a comparison circuit,
5-4 to 5-9 are AND circuits. 5-10 to 5-1
Reference numeral 5 indicates a buffer circuit with output control, and when its control terminal is "1", the output becomes high impedance. For each output of the AND circuits 5-4 to 5-9, for example, if the R input is maximum, the binary output RMAX from the AND circuit 5-4 becomes "1". The same applies to G and B. And each output RMAX, GMAX
, BMAX(7), the comparison circuits 5-1 to 5-3 are configured so that only one output is always "1", and M
A large amount of color information is output to the AX output. , Similarly, the minimum color information is output to the MIN output. Furthermore, if the R, G, and B inputs are equal, R is output to the MAX output, and G is output to the MIN output.

Next, the above-mentioned edge extraction circuit 4-16 will be explained with reference to FIG.

In the figure, the VCK input is an image transfer lock, the K input is luminance information, and the B output is binary information indicating whether or not it is an edge component. 6-1.6-2 is a D-FF (D-type flip-flop), which temporarily stores luminance information for three pixels. 6-3 is a double multiplication circuit; 6-4
．． 6-5 each indicate a subtraction circuit. Here, the luminance information of three consecutive pixels is sequentially divided into 2. If the value is 3, the subtraction circuit 6-5 calculates 2, 2-, and -, and if the result is equal to or greater than a certain value (the value of the register 6-6), the comparator circuit 6-5 treats it as an edge component. -7, “1” will be output to the B terminal.

[Other Embodiments] In the first embodiment, black character area probabilities are given to each of halftone, black dot, chromatic color, and contrast, and whether or not it is a black character area is determined based on the addition result of the probabilities. For example, even if the black character probability based on contrast is "0", if other probabilities are high, it may be determined that the area is a black character area overall. Therefore, in the second embodiment, a configuration is adopted in which it is possible to forcibly determine that each distribution amount is not a black character area or is a black character area, regardless of the other three types of distribution amounts.

<Second example> The second embodiment will be explained below with reference to FIG.

In FIG. 7, parts similar to those in the circuit of FIG. 4 have the same numerals, so a description thereof will be omitted.

In other words, the added part is the OR of 7-26.7-28
The circuit is a NOR circuit of 7-27, and an AND circuit of 7-29. And each table ROM7-18.7-24.
7-19.Regardless of other conditions, take out the signal to force a black character and the signal to force a non-black character from 7-25, and use the OR circuit 7-26 to OR the signal to force a black character. is taken, and a NOR circuit is used to force a signal that is not a black character to be NORed.

Next, if there is even one condition for forcing a black character by the OR circuit 7-28, the binary output is made into a black character area,
Furthermore, if there is even one condition that forces the area to be a non-black character using the AND circuit 7-29, the binary output is determined to be a non-black character area. This forced black character and the dominant light of the two conditions other than the forced black character are configured so that the characters other than the forced black character are given priority.

This is for areas that are numerically determined to be black text areas.
Since special image processing is applied, this is based on the premise that suspicious areas are not processed.

<Third Example> Next, the memory for storing the black character area probability described above is RAM.
, and the case where it is writable will be explained as an example.

The basic configuration is the same as shown in Figure 4 or Figure 7 above, and the contents to be written to the memory are prepared in advance in the ROM that stores the main program that controls the device, and initialized as necessary. Data will be written to RAM. Furthermore, numerically speaking, since the contents of the RAM are seldom changed, it is desirable to use a RAM with a backup so that the contents of the memory can be stored even when the power is turned off. The necessity and method of changing the contents of the RAM will be explained below.

In many cases, the documents used by the users who actually use the apparatus have characteristics. For example, when a text manuscript is often written in pencil, when printed text is used, and even when printed text is used, the size of the text may be unique to the user. In that case, even if you prepare only one type of black text area probability function, it is easy to misjudge, so prepare several types of black text area probability functions according to the manuscripts that are often used, and select the optimal function from among them. It is desirable to select .

FIG. 8 is a schematic block diagram showing the configuration of an apparatus when selecting a black character area probability function.

In the figure, 8-3 to 8-6 are 4-18.4-24°4-25
This is a RAM that stores the black character probability corresponding to the CPU.
8-7 is for reading and writing the contents. 8-1 is a ROM that stores the program for the CPU 8-7;
2 is a work RAM, 8-8 is an operating section of the apparatus, and 8-9 is a display section.

Further, 8-10 is an image processing and editing section that needs to be controlled by the CPU 8-7.

In the above configuration, several kinds of black character area functions corresponding to each type of character document are prepared in advance in the ROM 8-1, and the user selects the type using the operation section 8-8 and the display section 8-9. and instructs writing to RAMs 8-3 to 84. In response to this instruction, the CPU 8-7 selects each of the RAMs 8-3 to 8-6 from the ROM 8-1 according to the selected type.
Write the corresponding content to. Further, information on the selected type is displayed on the display section 8-9 so that the user can always recognize which type of function is currently selected.

Furthermore, each RAM8-3 to 8-6 is powered by a battery (not shown).
Back up the contents of , and save the unused area of RAM (
Write information indicating the type of function in the black text area (area not used as a function), and then turn the CPU 8-
7 reads the type information of each RAM 8-3 to 8-6,
The type can be displayed on the display section 8-9.

<Fourth Embodiment> A system configured with one memory for determining whether or not it is a single black character area for various conditions such as black dots, chromatic colors, and halftones will be described with reference to FIG.

In FIG. 9, the K%R, G, and B inputs are brightness, red, green, and blue color information, respectively, and the S output is binary information indicating whether or not the area is a black character area. 9-1
is a black character area probability table memory, which mainly determines whether the color is the color of a character or not. 9-2 is a counter that counts the color distribution of black characters. Reference numeral 9-3 is a table memory, which determines whether or not it is a black character area based on its distribution amount.Detailed control blocks are omitted, but similar to the counter described above, in this embodiment, The counter 9-2 is also configured to count the number of black character determination results within each predetermined area.

[Effects of the Invention] As explained above, according to the present invention, there are several types of conditions for determining a black text area, a function (relationship) of the black text area probability for each condition is found, and the black text area is comprehensively determined from each probability. By determining whether or not there is a black character area, it is possible to more accurately determine a black character area.

[Brief explanation of drawings]

FIG. 1 is an external perspective view showing the appearance of the image copying apparatus in the embodiment, FIG. 2 is a schematic block diagram showing the configuration of the image copying device in the embodiment, and FIGS. 3(a) to (d) are the black text areas. Figure 4 is a diagram showing the image area determination block in the first embodiment; Figure 5 is a diagram showing the maximum and minimum extraction blocks; Figure 6 is a diagram showing the edge extraction block. , FIG. 7 is a diagram showing the image area determination block in the second embodiment, FIG. 8 is a diagram showing the configuration in the third embodiment, and FIG. 9 is a diagram showing the configuration of the fourth embodiment.
FIG. 2 is a diagram showing a memory configuration in an embodiment. In the figure, 4-1.2, 9, 12.22... register, 4-3.
4, 10, 14.23... Comparison circuit, 4-5°13.
...AND circuit, 4-6.11, 15.17...Counter, 4-7...MAX, MIN extraction circuit, 4-8.
...Subtraction circuit, 4-16...Edge extraction circuit, 4-1
8.19, 24.25...ROM, 4-20...4
These are a manual addition circuit and a 4-21...k division circuit.

Claims (2)

[Claims] (1) In an image copying device that performs image area separation on input image information, processes the image based on the separated information, and copies the image, a step that calculates each of a plurality of distribution amounts for the image information is provided. a second calculating means for determining a black character area probability from each distribution amount determined by the first calculating means; determining a black character area from the black character area probability determined by the second calculating means; An image copying apparatus comprising a determining means and a copying means for processing and copying an image based on the result of the determining means. (2) The image copying apparatus according to claim 1, wherein the plurality of distribution amounts are respective distribution amounts of halftone, black dot density, contrast, and chromatic color.