JP2001075428A - Device and method for forming image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device that an inputted adjustment value and an actually set threshold are sensuously matched and the adjustment value is easily set by discriminating whether it is color or monochromatic by the threshold linearly decided to the inputted adjustment value. SOLUTION: Whether it is color or monochromatic is discriminated by the threshold linearly decided to the inputted adjustment value. In this device, an adjustment value input means 64 calculates the threshold C2 corresponding to the adjustment value inputted by a user. A color pixel counting means 63 counts the number C1 of pixels judged as color pixels in a pixel color/ monochromatic judgment means 62 and sends it to an original color/ monochromatic discrimination part 65. The original color/monochromatic discrimination part 65 compares the number C1 of the pixels counted by the color pixel counting means 63 with the threshold C2 set by the adjustment value input means 64. As the result of comparison, an original is discriminated as monochromatic in the case of C1<C2 and the original is discriminated as color in the case of C1>C2 or C1=C2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a digital copying machine capable of performing color copying and an image forming method.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a digital copying machine capable of performing color copying, it is determined whether a document is color or monochrome (monochrome monochrome). Some have the function of performing

As described above, the process of switching between color copy and monochrome copy according to the original is performed by reading the image of the original by prescanning or the like and determining whether each pixel of the read original image is a color pixel or a monochrome pixel. If the number of color pixels exceeds a certain threshold, the document is determined to be color. For this reason, when adjusting the original to be copied in color and the original to be copied in black and white, the user adjusts the automatic determination by changing the threshold value as described above.

Such a method of determining a threshold value for determining whether a document is color or monochrome has a linear characteristic with respect to an adjustment value that can be adjusted by an administrator of the image forming apparatus.

In this case, since copying in color is more expensive than that in monochrome, the administrator usually wants to copy in monochrome if the document has a small number of color areas. . Therefore, it is necessary that the adjustment value and the color / monochrome determination result match sensuously. For example, (A) When the original is almost monochrome, that is, an original in which one seal is stamped in the original is desired to be copied in monochrome, but if two originals are stamped, color is used. In such a case, since the number of color pixels in the whole original document is small, the point where the determination result is switched to a delicate threshold value change is exceeded. Therefore, it is better that the threshold value for the adjustment value can be finely adjusted (on the order of several to several tens of pixels).

(B) On the other hand, when it is desired to convert a document including a large number of color pixels to monochrome, it is difficult to recognize the effect even if fine adjustment is performed. Therefore, it is better that the threshold value can be roughly adjusted (on the order of several hundreds to several thousand pixels).

Simultaneously satisfying the above requirements (A) and (B) cannot be realized because the threshold value is determined linearly with respect to the adjustment value.

In order to confirm whether or not the judgment result of the document based on the adjustment value input by the administrator is satisfactory,
Every time the adjustment value was changed, it was necessary to actually make a copy and check it.

[0009]

As described above, since color or monochrome is determined by a threshold value which is linearly determined for an input adjustment value, the input adjustment value is actually set to the input adjustment value. An image forming apparatus and an image forming method for solving the problem that threshold values do not match sensuously, wherein the input adjustment value and the actually set threshold value sensibly match, and the adjustment value is easily set. The purpose is to do.

Another object of the present invention is to solve the problem that it is necessary to execute a copying operation in order to confirm an actual judgment result with respect to an inputted adjustment value. In addition, the present invention provides an image forming apparatus and an image forming method capable of easily confirming a determination result without executing a copy operation.

[0011]

An image forming apparatus according to the present invention has an input means for inputting an adjustment value for determining whether a document is color or black and white, and a first derivative for the adjustment value input by the input means. Setting means for setting a threshold value having a characteristic that monotonically increases, determining means for determining the number of chromatic pixels from the image of the document, and the number of chromatic pixels determined by this determining means (1) discriminating means for discriminating whether a document is color or black and white based on whether or not it is equal to or greater than a threshold value set by the setting means of (1); When the document is determined to be black and white, a second setting means is provided for setting an image forming mode in black and white.

According to the image forming apparatus of the present invention, there is provided input means for inputting an adjustment value for determining whether a document is color or black and white, wherein the first derivative monotonically increases with respect to the adjustment value input by the input means. First setting means for setting a threshold having characteristics; determining means for determining the number of chromatic pixels from an image of a document; and the number of chromatic pixels determined by the determining means is set by the first setting means. Discriminating means for discriminating whether a document is color or black and white based on whether or not the threshold value is equal to or greater than a threshold value. The second setting means for setting the image forming mode in black and white, and the above-mentioned judgment before starting the image forming operation in the image forming mode set by the second setting means. And a display means for displaying a determination result by the stage.

According to the image forming apparatus of the present invention, there is provided input means for inputting an adjustment value for determining whether a document is color or black and white, wherein the first derivative monotonically increases with respect to the adjustment value input by the input means. First setting means for setting a threshold having characteristics, reading means for converting each pixel of the image of the document into electric signals for each of a plurality of color components and reading the signals, and represented by signals of the respective color components read by the reading means. Determining means for determining whether each pixel is a predetermined chromatic color; counting means for counting the number of pixels determined to be chromatic by the determining means; chromatic colors present in the image of the document counted by the counting means Determining whether the original is color or black and white based on whether the number of pixels is equal to or greater than the threshold value set by the first setting means, and determining that the original is color by this determining means To, to set the image forming mode by the color, when a document is determined to be monochrome, and a second setting means for setting an image forming mode by black and white.

According to the image forming apparatus of the present invention, there is provided input means for inputting an adjustment value for determining whether a document is color or black and white, wherein the first derivative monotonically increases with respect to the adjustment value input by the input means. First setting means for setting a threshold having characteristics, reading means for converting each pixel of the image of the document into electric signals for each of a plurality of color components and reading the signals, and represented by signals of the respective color components read by the reading means. Determining means for determining whether each pixel is a predetermined chromatic color; counting means for counting the number of pixels determined to be chromatic by the determining means; chromatic colors present in the image of the document counted by the counting means Determining means for determining whether the document is color or black and white based on whether or not the number of pixels is equal to or greater than the threshold value set by the first setting means. When the determination means determines that the document is color, A second setting means for setting an image forming mode in black and white when the original is determined to be black and white, and an image forming mode set by the second setting means. Before starting the image forming operation, the display means is configured to display a result of the determination by the determination means.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 schematically shows an internal configuration of an image forming apparatus such as a digital color copying machine for reading a color image or a monochrome image on a document and forming a duplicate image thereof according to the present invention. This image forming apparatus is roughly classified into a color scanner unit 1 as an image reading unit for reading and inputting a color image on a document, and a color printer unit 2 as an image forming unit for forming a duplicate image of the input color image. It is composed of

The color scanner unit 1 has a document table cover 3 on the upper part thereof, and has a document table 4 made of a transparent glass on which a document is set, disposed opposite to the document table cover 3 in a closed state. ing. An exposure lamp 5 for illuminating the original placed on the original table 4, a reflector 6 for condensing light from the exposure lamp 5 on the original, and a reflected light from the original under the original table 4. A first mirror 7 and the like that are bent leftward with respect to the drawing are provided. The exposure lamp 5, the reflector 6, and the first mirror 7 are fixed to a first carriage 8. The first carriage 8 is driven by a pulse motor (not shown) via a toothed belt (not shown) or the like, so as to be translated along the lower surface of the document table 4.

The left side of the first carriage 8 in the figure, that is, the direction in which the light reflected by the first mirror 7 is guided, is driven via a drive mechanism (not shown) (for example, a toothed belt and a DC motor). A second carriage 9 movably provided in parallel with the document table 4 is provided.
On the second carriage 9, there is provided a second mirror 1 for bending the reflected light from the document guided by the first mirror 7 downward in the drawing.
The first and third mirrors 12 that bend the reflected light from the second mirror 11 rightward in the figure are arranged at right angles to each other. The second carriage 9 is driven by the first carriage 8 and is moved in parallel with the first carriage 8 along the document table 4 at a half speed.

An image forming lens 13 for forming an image of the reflected light from the third mirror 12 at a predetermined magnification is disposed in a plane including the optical axis of the light turned back by the second and third mirrors 11 and 12. A CCD type color image sensor (photoelectric conversion element) that converts reflected light given converging properties by the imaging lens 13 into an electric signal in a plane substantially orthogonal to the optical axis of the light passing through the imaging lens 13. 15 are provided.

When the light from the exposure lamp 5 is condensed on the document on the document table 4 by the reflector 6, the light reflected from the document is reflected by the first mirror 7, the second mirror 11, the third mirror 12, Then, the light enters the color image sensor 15 via the imaging lens 13, where the incident light is converted into an electric signal corresponding to the three primary colors of R (red), G (green), and B (blue). .

The electric signals corresponding to the R, G, and B have values indicating the gradation of each color. For this reason, when the read pixel is white or black, R, G, and B are both values close to the maximum gradation or the minimum gradation, and the values of the R, G, and B colors are substantially the same. When the read pixel is a chromatic color other than white or black, R, G, and B have different halftones, and R, G, and B have different values.

The color printer unit 2 performs color separation for each color component based on a well-known subtractive color mixing method, ie, yellow (y), magenta (m), cyan (c),
And first to fourth image forming units 10y, 10m, 10c, 1 for forming four color images of black (k), respectively.
0k.

Each of the image forming units 10y, 10m, 10c, 1
Below 0k, a transport mechanism 20 for transporting the copy paper taken out from the paper cassette 22a or 22b and transporting the copy paper on which the image for each color is formed by each image forming unit is provided.

Each of the image forming units 10 is
In the direction in which the copy sheet that has passed through y, 10m, 10c, and 10k is further transported, the copy sheet is heated to a predetermined temperature to melt the toner image transferred to the copy sheet, and fix the toner image to the copy sheet. A fixing device 22 is provided.

The image forming units 10y, 10m, 10
Above c and 10k, an exposure device 24 for forming an electrostatic latent image separated into each color on each image forming unit is provided.

FIG. 2 is a block diagram schematically showing the electrical connection of the image forming apparatus shown in FIG. 1 and the flow of signals for control.

As shown in FIG. 2, the control system of the image forming apparatus includes a main control unit 30, a color scanner unit 1, a printer unit 2, and an operation panel 40.

The main control unit 30 includes a main CPU 31, an RO
M (read only memory) 32, RAM 33, NV
It comprises a RAM 34, a shared RAM 35, an image processing unit 36, a page memory control unit 37, and a page memory 38.

The main CPU 31 controls the overall control. The ROM 32 stores a control program and the like. The RAM 33 temporarily stores data.

An NVRAM (Non-Volatile RAM) 34 is a nonvolatile memory backed up by a battery (not shown), and retains stored data even when the power is turned off. .

The shared RAM 35 is used for performing bidirectional communication between the main CPU 31 and the scanner CPU 110 or the printer unit.

The image processing section 36 has a document judging section 36a for judging whether the image read by the scanner is color or monochrome (black and white), and performs various processes on the input image.

The page memory control section 37 stores and reads out image information from and to the page memory 38. The page memory 38 has an area in which image information for a plurality of pages can be stored, and is formed so that data obtained by compressing image information from the color scanner unit 1 can be stored for each page.

The operation panel 40 includes a liquid crystal display section 42, various operation keys 43, and a panel CP to which these are connected.
It has U41 and is connected to the main CPU31.

The color scanner section 1 includes a scanner CPU 51 for controlling the entire system, a ROM 52 for storing a control program and the like, a RAM 53 for data storage, a CCD driver 54 for driving the color image sensor 15,
It comprises a scanning motor driver 55 for controlling the rotation of a scanning motor for moving the first carriage 8 and the like, an image correction unit 56 and the like.

The image correction unit 56 includes an A / D conversion circuit for converting R, G, and B analog signals output from the color image sensor 15 into digital signals, variations in the color image sensor 15, or ambient temperature. It comprises a shading correction circuit for correcting a threshold level fluctuation with respect to an output signal from the color image sensor 15 due to a change, etc., and a line memory for temporarily storing a digital signal subjected to shading correction from the shading correction circuit. ing.

The printer unit 2 includes the main CPU 3
A color copy mode for performing color image formation (color image formation mode) or a monochrome copy mode for monochrome image formation (black and white image formation mode) is set based on the control of 1.

Next, a document judging section 36 in the image processing section 36
a will be described. FIG. 3 is a block diagram showing a configuration of the document determination unit 36a.

As shown in FIG. 3, the document judging section 36a
It comprises a pixel color / monochrome determination unit 62, a color pixel counting unit 63, an adjustment value input unit 64, a document color / monochrome determination unit 65, and a determination result display unit 66.

The pixel color / monochrome determination means 62
Is to determine whether each pixel of the image of the document read by the scanner unit (image input means) 1 is color or monochrome. The color pixel counting unit 63 counts the number of pixels determined as color pixels by the pixel color / monochrome determination unit 62.

The adjustment value input means 64 sets a threshold value for determining whether a document is a color document or a monochrome document based on the adjustment value input from the operation keys 43 of the operation panel 40. is there. The document color / monochrome determination unit 65 compares the threshold value set by the adjustment value input unit 64 with the color pixels counted by the color pixel counting unit, and determines whether the document is color / monochrome.
The determination result display means 66 determines the result of the color / monochrome determination of the document (whether the document is color or monochrome).
Is displayed on the liquid crystal display section 42 of the operation panel 40.

The scanner section 1 performs pre-scanning of a document when determining whether the document is color or monochrome.
This prescan is performed at a resolution lower than the resolution used at the time of copying to increase the scanning speed (for example, 600 dpi in the main scanning direction and 200 dpi in the sub scanning direction).

The pixel color / monochrome determination means 62
Pixel data of the image data supplied to R, G, B
In three colors. The color / monochrome determination means 62 of the pixel combines two of the three color components R, G, and B, and performs three combinations of R-G, G-B, and B-R. If any one of the three absolute values of the difference exceeds a predetermined threshold, it is determined that the pixel is a color pixel.

The original color / monochrome discriminating means 65
If the number of color pixels counted by the color pixel counting means 63 is C1, the threshold value C2 set in the adjustment value input means 64 is C1 <C2, the document is determined to be monochrome, and C1> When C2 or C1 = C2,
The original is determined to be color.

Next, the threshold value C2 for determining whether the original set by the adjustment value input means 64 is color or monochrome will be described.

The threshold value C2 is a value determined based on an adjustment value input by the operation keys 43 of the operation panel 40. The adjustment value is changed each time an adjustment key (not shown) provided as one of the operation keys 43 is pressed. This adjustment key includes, for example, an increase key for increasing the adjustment value and a decrease key for decreasing the adjustment value. When the adjustment value is n (0 ≦ n ≦ 255), every time one increase key is pressed down The adjustment value becomes n + 1, and the adjustment value becomes n-1 each time one decrease key is pressed.

The threshold value C2 for such an adjustment value n is
In a portion where the adjustment value is small, the threshold value C2
Gradually changes, and in a portion where the adjustment value is large, the threshold value C2
Change rapidly.

That is, as shown in FIG. 5, the threshold value C2 gradually changes in the portion where the adjustment value n is small. Therefore, the threshold value C2 is finely adjusted with respect to the change of the adjustment value n. On the other hand, in a portion where the adjustment value n is large, the threshold value C2 changes rapidly. Therefore, the threshold value C2 is roughly adjusted with respect to a change in the adjustment value.

Thus, the change in the discrimination result with respect to the change in the adjustment value input to the operation panel 40 can be changed so as to match the feeling of a user such as a manager who inputs the adjustment value.

The threshold value C2 for the adjustment value n is calculated by the following equation having the characteristic that the first derivative monotonically increases.

C2 = total number of pixels × 2 ^{(n / 8)} / 10 ^{8 In} the above formula for determining the threshold value C2, which expresses the same effect as above, the general form is C2 = A × X ^Bn (A, B: positive constant, X: real number of 1 or more) C2 = C × n ^D (C, D: positive constant) C2 = E × tan (Fn) (E: positive constant, F : A positive real number, the value of which the function is continuous in the range of the adjustment value n) C2 = K × arcsin (Ln) (K: positive constant,
L: a positive real number whose product with the maximum value of the adjustment value n is 1 or less,
arcsin (Ln) is used only in the range of 0 to π / 2)
And the like.

Next, the operation of adjusting the threshold value when automatically judging between color and monochrome according to the original will be described with reference to FIG.
This will be described with reference to the flowchart shown in FIG.

First, a user such as an administrator inputs an adjustment value n using the operation keys 43 of the operation panel 40 (step 1). Then, the adjustment value input unit 64 calculates a threshold value C2 according to the input adjustment value n (Step 2). The calculated threshold value C2 is set in the original color / monochrome discriminating unit 65 by the adjustment value input unit 64.

When a user such as an administrator instructs the start of pre-scanning with the operation keys 43 of the operation panel 40, the scanner unit 1 performs an original reading operation at a predetermined pre-scan resolution (step 3). . The read image of the document is supplied from the scanning unit (image input unit) 1 to the pixel color / monochrome determination unit 62.

The pixel color / monochrome determination means 62
It is determined whether or not the read image of the document is a color pixel based on the R, G, and B color components for each pixel (step 4). This determination result is sent to the color pixel counting means 63.

The color pixel counting means 63 counts the number C1 of pixels determined as color pixels by the pixel color / monochrome determination means 62 (step 5) and sends it to the original color / monochrome determination section 65.

The original color / monochrome discriminating section 65 calculates the number C1 of pixels counted by the color pixel counting means 63.
Is compared with the threshold value C2 set by the adjustment input means 64 in step 2 described above. As a result of this comparison, C1
If <C2, the document is determined to be monochrome, and if C1> C2 or C1 = C2, the document is determined to be color (step 6).

When the original is determined to be color based on the determination result, the main CPU 31 sets the copy mode to the color copy mode (step 7). At this time, the determination result display means 66 displays on the liquid crystal display section 42 of the operation panel 40 that the document is determined to be color (step 8). If the document is determined to be monochrome based on the above determination result, the main CPU 31 sets the copy mode to the monochrome copy mode (step 9). At this time, the determination result display means 66 is provided on the liquid crystal display unit 4 of the operation panel 40.
2 indicates that the document is determined to be monochrome (step 10).

If the result of the judgment of the document displayed on the liquid crystal display section 42 is not satisfactory, the administrator presses the cancel key with the operation key 43 of the operation panel 40 (step 11). As a result, the process returns to step 1 and the adjustment value is input again.

If the judgment result of the document displayed on the liquid crystal display section 42 is satisfactory, the administrator presses the copy key with the operation key 43 of the operation panel 40 (step 12). As a result, the image forming apparatus performs a main scan of the document and performs a copy operation (step 13).

As described above, the judgment result of the original image obtained by the prescan is displayed, and if the judgment result is satisfactory, the main scan is performed and the copy is executed, and the judgment result is satisfactory. If not, the adjustment value is corrected again.

Thus, instead of performing the determination after all of the determination results after performing the copy operation, the operation of re-adjusting the displayed determination results until a satisfactory result is obtained is repeated. And unnecessary copy output can be avoided.

[0063]

As described above in detail, according to the present invention, it is possible to provide an image forming apparatus in which the input adjustment value and the actually set threshold value are intuitively matched, and the adjustment value can be easily set.

According to the present invention, there is provided an image forming apparatus and an image forming method capable of easily confirming a discrimination result without executing a copying operation when confirming an actual decision result with respect to an input adjustment value. it can.

[Brief description of the drawings]

FIG. 1 is a diagram showing an internal configuration of an image forming apparatus such as a digital color copying machine according to an embodiment of the present invention.

FIG. 2 is a block diagram schematically showing a flow of signals for electrical connection and control of the image forming apparatus shown in FIG. 1;

FIG. 3 is a block diagram schematically showing a configuration of a document determination unit.

FIG. 4 is a diagram illustrating a relationship between an adjustment value and a threshold.

FIG. 5 is a diagram illustrating a relationship between an adjustment value and a threshold.

FIG. 6 is a flowchart illustrating an operation of adjusting a threshold when automatically determining whether a document is color or monochrome according to a document.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Scanner part 2 ... Printer part 30 ... Main control part 31 ... Main CPU 36 ... Image processing part 36a ... Original judgment part 40 ... Operation panel 42 ... Liquid crystal display part 43 ... Operation keys 62 ... Pixel color / monochrome judgment means 63 ... Color pixel counting means 64 ... Adjustment value input means 65 ... Document color / monochrome discriminating means 66 ... Discrimination result display means

Continued on front page F-term (reference) 2H027 DE07 ED06 EE07 FA28 FB06 FD08 GB13 ZA07 2H030 AB02 AD07 BB02 BB21 BB41 5C079 HA13 JA12 LA01 LA03 LA31 MA19 MA20 NA17 NA27 PA02

Claims (9)

[Claims] An input means for inputting an adjustment value for determining whether a document is color or black and white, and a threshold value having a characteristic such that the first derivative monotonically increases with respect to the adjustment value input by the input means. First to set
Setting means; determining means for determining the number of chromatic pixels from the image of the document; and determining whether the number of chromatic pixels determined by the determining means is equal to or greater than the threshold value set by the first setting means And a discriminating means for discriminating whether the document is color or black and white.When the discriminating means determines that the document is color, an image forming mode in color is set. And second setting means for setting a black and white image forming mode. 2. An input means for inputting an adjustment value for determining whether a document is color or black and white, and a threshold having a characteristic such that the first derivative monotonically increases with respect to the adjustment value input by the input means. First to set
Setting means; determining means for determining the number of chromatic pixels from the image of the document; and determining whether the number of chromatic pixels determined by the determining means is equal to or greater than the threshold value set by the first setting means Means for discriminating whether the document is color or black and white, means for re-setting by the first setting means based on the result of discrimination between black and white or color by the discrimination means, and discrimination that the document is color. Setting a color image forming mode, and setting a black and white image forming mode when a document is determined to be black and white. apparatus. 3. An input means for inputting an adjustment value for determining whether a document is color or black and white, and a threshold value having a characteristic such that the first derivative monotonically increases with respect to the adjustment value input by the input means. First to set
Setting means; determining means for determining the number of chromatic pixels from the image of the document; and determining whether the number of chromatic pixels determined by the determining means is equal to or greater than the threshold value set by the first setting means And a discriminating means for discriminating whether the document is color or black and white.When the discriminating means determines that the document is color, an image forming mode in color is set. A second setting means for setting an image forming mode in black and white, and a display for displaying a judgment result by the judging means before starting an image forming operation in the image forming mode set by the second setting means. And an image forming apparatus. 4. An input means for inputting an adjustment value for determining whether a document is color or black and white, and a threshold value having a characteristic such that the first derivative monotonically increases with respect to the adjustment value input by the input means. First to set
Setting means, reading means for converting each pixel of the image of the document into an electric signal for each of a plurality of color components, and reading the image. Each pixel represented by the signal of each color component read by the reading means is provided with a predetermined chromatic color. Determining means for determining whether or not the number of pixels determined to be chromatic by the determining means; counting means for counting the number of pixels determined to be chromatic by the determining means; A discriminating means for discriminating whether the document is color or black and white based on whether or not the value is equal to or greater than a threshold value set by the first setting means; And a second setting unit that sets a mode and sets an image forming mode in black and white when it is determined that the document is black and white. 5. An input means for inputting an adjustment value for determining whether a document is color or black and white, and a threshold value having a characteristic such that the first derivative monotonically increases with respect to the adjustment value input by the input means. First to set
Setting means, reading means for converting each pixel of the image of the document into an electric signal for each of a plurality of color components, and reading the image. Each pixel represented by the signal of each color component read by the reading means is provided with a predetermined chromatic color. Determining means for determining whether or not the number of pixels determined to be chromatic by the determining means; counting means for counting the number of pixels determined to be chromatic by the determining means; A discriminating means for discriminating whether the document is color or black and white based on whether or not the value is equal to or greater than a threshold value set by the first setting means; A second setting means for setting an image forming mode in black and white when the original is determined to be black and white, and an image forming operation in the image forming mode set by the second setting means. Before starting the image forming apparatus characterized by comprising display means for displaying the discrimination result by the discriminating means. 6. The method according to claim 1, wherein the first setting means sets a threshold value calculated by a total number of pixels × 2 ^{(n / 8)} / 10 ⁸ with respect to the adjustment value n. The image forming apparatus according to claim 1. 7. An adjustment value for judging whether a document is color or black and white is set, and a threshold value having a characteristic such that the first derivative monotonically increases with respect to the input adjustment value is set. From the above, the number of chromatic pixels is determined, and whether the document is color or black and white is determined based on whether the determined number of chromatic pixels is equal to or greater than the set threshold value. When determined,
An image forming method comprising: setting a color image forming mode; and setting a black and white image forming mode when a document is determined to be black and white. 8. An adjustment value for judging whether the original is color or black and white, and a threshold value having a characteristic such that the first derivative monotonically increases with respect to the input adjustment value is set. , The number of chromatic pixels is determined from, and whether the document is color or black and white is determined based on whether the determined number of chromatic pixels is equal to or greater than the set threshold value. Based on the result, the threshold value is set again by inputting the adjustment value, and when the original is determined to be color, an image forming mode in color is set, and when the original is determined to be black and white, Setting an image forming mode in black and white. 9. An adjustment value for judging whether a document is color or black and white is set, and a threshold value having a characteristic such that the first derivative monotonically increases with respect to the input adjustment value is set. From the above, the number of chromatic pixels is determined, and whether the document is color or black and white is determined based on whether the determined number of chromatic pixels is equal to or greater than the set threshold value. When determined,
A color image forming mode is set, and when it is determined that the document is black and white, the image forming mode in black and white is set, and before the image forming operation in the set image forming mode is started, the document is An image forming method, comprising: displaying a determination result of black and white or color.