JPH07264415A - Method and device for image processing - Google Patents

Abstract

PURPOSE:To provide a method and a device for image processing discriminating whether or not an original is a color original correctly. CONSTITUTION:A black picture element discrimination section 104 discriminates a black picture element of image data, an average value arithmetic section 105 calculates an average value of the image data except the discriminated black picture element and a subtractor 107 subtracts the calculated average value from the image data. A color/black/white level discrimination section 108 discriminates whether the original for the image data is a color original or a black/white original based on the result of subtraction. A control section 104 codes the image data by using a black/white coding section 114 or a color coding section 115 depending on the result of discrimination.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing method and an apparatus thereof, and more particularly, to an image processing method and an apparatus thereof for a facsimile apparatus which performs color / black and white automatic switching transmission.

[0002]

2. Description of the Related Art A monochrome facsimile machine and a color facsimile machine transmit images using different encoding systems. However, it is wasteful in terms of space and money to separately install the color facsimile apparatus and the G4 or G3 facsimile apparatus, and a facsimile apparatus capable of transmitting color images and black-and-white images by one unit is desired. Therefore, the applicant automatically determines whether an image read by an image scanner or the like is in color or black and white,
A facsimile apparatus has been proposed which encodes an image by a corresponding encoding method and transmits it.

[0003]

However, the above-mentioned conventional example has the following problems. That is, when the paper on which the original is recorded is recycled paper, the background of the image may be slightly colored, but in such a case, it is possible to determine it as color and send it as a black and white image. However, there was a drawback that it was sent as a color image.

The present invention is intended to solve the above-mentioned problems, and its purpose is as follows. It is an object of the inventions of claims 1, 5, 7, 11, 14 and 16 to correctly determine whether or not a document is in color by extracting background color information of image data. It is another object of the present invention to store the color information of the recording medium so as to correctly determine whether or not the original is color.

It is another object of the inventions of claims 3 and 13 to correctly determine whether or not the original is color by extracting the color information of the recording medium.

[0006]

However, the above-mentioned conventional example has the following problems. That is, the image processing apparatus according to the present invention determines an extraction unit that extracts background color information of image data, and a determination whether the original of the image data is color based on the color information extracted by the extraction unit. Means and an encoding means for encoding the image data according to the determination result of the determining means.

Further, storage means for storing color information of at least one recording medium, determination means for determining whether or not the original of the image data is color based on the color information read from the storage means, and the determination means. And an encoding unit that encodes the image data according to the determination result. Further, an extracting means for extracting the color of the recording medium, a storage means for storing at least one color information extracted by the extracting means, and whether the original of the image data is color based on the color information read from the storing means. It is characterized by having a judging means for judging whether or not there is, and a coding means for coding the image data according to the judgment result of the judging means.

Further, a discriminating means for discriminating black pixels of the image data, a calculating means for calculating an average value of the image data excluding the black pixels discriminated by the discriminating means, and an average value calculated by the calculating means. Subtracting from the image data, determining means for determining whether the original of the image data is color based on the subtraction result of the subtracting means, and encoding the image data according to the determination result of the determining means. And a coding means for converting the data into a character.

Further, a discriminating means for discriminating a black pixel of the image data, a calculating means for calculating an average value of the image data excluding the black pixels discriminated by the discriminating means, and a calculating means for calculating the average value from the image data. Subtraction means for subtracting the average value, storage means for storing at least one subtraction result of the subtraction means, selection means for selecting a subtraction result to be read from the storage means, and the storage means selected by the selection means Determination means for determining whether or not the original of the image data is color based on the subtraction result read from
Coding means for coding the image data according to the judgment result of the judging means.

Further, a discriminating means for discriminating black pixels of the image data, a calculating means for calculating an average value of the image data excluding the black pixels discriminated by the discriminating means, and a calculating means for calculating the image data from the image data. Subtracting means for subtracting the average value, determining means for determining whether or not the original of the image data is color based on the subtraction result of the subtracting means, and the subtraction result is encoded according to the determination result of the determining means. And a coding means for converting the data into a character.

According to the image processing method of the present invention, an extraction process for extracting background color information of image data and a determination as to whether or not the original of the image data is color based on the color information extracted in the extraction process. And a coding process for coding the image data according to the determination result of the determination process. Further, color information of at least one recording medium is stored in the storage means, it is determined whether or not the original of the image data is color based on the color information read from the storage means, and the image data is determined according to the determination result. Is encoded.

Further, the extracted color information of the recording medium is stored in the storage means, and it is determined whether the original of the image data is color based on the color information read from the storage means for storing the color information of at least one recording medium. Is determined and the image data is encoded according to the determination result. In addition, a determination process for determining a black pixel of image data,
A calculation step of calculating an average value of the image data excluding the black pixels determined in the determination step, a subtraction step of subtracting the average value calculated in the calculation step from the image data, and a subtraction result of the subtraction step. It is characterized in that it has a judging step for judging whether the original of the image data is color based on the above, and an encoding step for coding the image data according to the judgment result of the judging step.

Further, a discrimination process for discriminating black pixels of the image data, a calculation process for calculating an average value of the image data excluding the black pixels discriminated in the discrimination process, and an average value calculated in the calculation process. A subtraction step for subtracting from the image data, a storage step for storing the subtraction result of the subtraction step in a storage means, and a selection step for selecting a subtraction result to be read from the storage means for storing at least one subtraction result, A determination step of determining whether or not the original of the image data is color based on the subtraction result selected in the selection step and read from the storage means, and the image data is encoded according to the determination result of the determination step. And an encoding step.

Further, a discrimination process for discriminating black pixels of the image data, a calculation process for calculating an average value of the image data excluding the black pixels discriminated in the discrimination process, and an average value calculated in the calculation process. Subtraction step for subtracting from the image data, a determination step for determining whether or not the original of the image data is color based on the subtraction result of the subtraction step, and the subtraction result is encoded according to the determination result of the determination step. And an encoding step for converting.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image processing apparatus according to an embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram showing an example of the configuration of a facsimile apparatus that performs color / monochrome automatic switching transmission.

In the figure, 120 is a control unit, which is a CPU, RO
Each component, which is composed of M, RAM, I / O, etc., is controlled via a bus or a signal line (not shown) according to a program stored in a ROM or the like. An operation unit 121 includes a keyboard for inputting an instruction or the like from the user to the control unit 120, and a display unit such as an LCD for displaying the operation status / conditions of the apparatus sent from the control unit 120.

Reference numeral 101 denotes an image scanner, which detects reflected light of an original image by a sensor for each color of RGB, and outputs, for example, each 8-bit RGBX image signal corresponding to the amount of reflected light, as shown in an example in FIG. 4A. Output serially in synchronization with CK1, CK2, CK3. The signal VE represents the effective area of the image signal. Also, R is red, G is green, B is blue, and X
Is indeterminate.

Reference numeral 102 denotes a scanner interface, which electrically matches the image scanner 101.
A gamma converter 103 performs gamma correction on the signal input from the scanner interface 102 in order to correct the reading characteristics of the image scanner 101. A color / monochrome discriminating unit 108 discriminates whether the document image read by the image scanner 101 is color or monochrome. Specifically, the RGB data input from the γ conversion unit 103 is matrix-converted to Y
The pixel is converted into IQ data, a pixel whose absolute value of the I data or Q data exceeds a predetermined threshold value is detected, the detected pixel is counted within a predetermined image area, and determination is performed based on the count result. In other words, if there is an image area in which the count value on one page of the image exceeds the specified value, it is determined to be a color document, and if not, it is determined to be a monochrome document.

Reference numeral 109 is a black data generation unit, which is a γ conversion unit 10.
Perform the sum of products operation using the RGB data input from
(Black) Generate data. The black data generator 109 is shown in FIG.
As shown in B, the generated K data is input to R
Insert it in the X part of GBX data and output it as RGBK data. Reference numeral 110 denotes a pixel density conversion unit, which is a black data generation unit 109.
The image signal input from is subjected to scaling processing and resolution conversion.

Reference numeral 111 denotes a binarization unit, which is a pixel density conversion unit 11
The multi-valued data input from 0 is binarized. Reference numeral 112 denotes a serial-parallel conversion unit, which is composed of, for example, a shift register, and as shown in FIG.
Serial-parallel conversion is performed by shifting the RGBK serial data input from 1 at the falling edge of the clock CK4 and outputting 4 bits collectively at the rising edge of the clock CK1.

A page memory 113 temporarily stores the 4-bit image data input from the serial-parallel converter 112 in page units. Reference numeral 114 denotes a black-and-white encoding unit for converting a black-and-white image, that is, an image represented by K data into MMR, MR, MH.
It is encoded by an encoding method such as, and outputs 8-bit encoded data. A color encoding unit 115 encodes a color image, that is, an image represented by RGB 3 bits by a dot sequential binary color encoding method, and outputs 8-bit encoded data.

A code buffer 116 temporarily stores code data. 117 is a hard disk (hereinafter "HD")
That is, the code data input via the code buffer 116 and the code data received from the line 119 are collectively stored. Reference numeral 118 is a communication control unit (hereinafter referred to as “CCU”), and 119 is a line such as ISDN, PSTN or a dedicated line.

2A and 2B are views showing an example of an operation panel of the operation unit 121. In the figure, 201 is a one-touch dial key for performing one-touch dial transmission, and 202 is a numeric keypad for inputting dials and other numbers. Reference numeral 203 denotes a dial key that indicates that the key to be pressed thereafter when dialing is a dial.
4 is a subaddress key that indicates that the key to be pressed after dialing is an ISDN subaddress, 205 is a speed dial key that indicates that the key to be pressed after that is a speed dial is speed dial, and 206 is the dial immediately before. This is a redial key that repeats the dialed.

Reference numeral 207 is a cursor key for moving the cursor on the LCD 215, 208 is a FAX / copy switching key for switching between the facsimile mode and the copy mode, 210 is a set key for setting data such as dials, and 211 is an input such as dials. A clear key that erases data. Reference numeral 212 is a storage key for reading an original image and storing it in a memory, 213 is a start key for starting facsimile transmission or copying, 214 is a stop key for stopping an operation or operation, 215 is a date and time, a mode, dial, etc. are necessary. LCD displaying information 216
Is an error indicator that displays error messages such as running out of ink and running out of paper.

Reference numeral 217 is a document size selection key for selecting the size of the document to be read, and 218 is a document size selection key 217.
A document size indicator 219 for displaying the document size selected by means of a cassette selection key for selecting a transmission image size for facsimile transmission and a size for recording paper for copying, and 220 for displaying the size selected by the cassette selection key 219. It is a size indicator.

Reference numeral 221 denotes a resolution selection key for selecting an image resolution for facsimile transmission, and 222 denotes a resolution selection key 2
A resolution indicator for displaying the resolution selected by 21;
Reference numeral 223 is a read density setting key for setting the read density of the original image, and 224 is a read density indicator for displaying the read density set by the read density key 223. 225, when binarizing an image to be transmitted by facsimile, performs binarization for a text original (for example, simple binarization) or binarizes for a photo original (for example, by providing a pseudo gradation by dither processing). Binarization method selection key 226 for selecting whether to perform
Is a binarization method display that displays the binarization method selected by the binarization method selection key 225. The binarization method display 227 transmits the color image, the monochrome image, or the original image automatically. An encoding method selection key 228 for discriminating color / black and white and selecting whether to transmit according to the discrimination result is an encoding method display for displaying the encoding method selected by the encoding method selection key 227. is there.

FIG. 3 is a flow chart showing an example of a procedure for automatic color / monochrome switching transmission performed by the apparatus shown in FIG. 1, and shows the procedure for one page of the original. When the start key 213 or the accumulation key 212 is pressed, in step S401,
Parameters such as the selected / set document size, transmission image size, resolution, read density, and binarization method are set in each image processing unit, and in step S408, the image scanner 1
01 starts reading the original image.

Subsequently, in step S409, the read image data is processed by the above-described configuration, and the process waits until one page of image data is stored in the page memory 113. When the processing of the image data for one page is completed, the color / monochrome discriminating unit 108 discriminates whether the read image is color or monochrome in step S410, and the process branches depending on the result.

If the determination result is black and white, step S411
Then, the black-and-white encoding unit 114 starts encoding, and in step S412, it is determined whether or not encoding for one page is completed.
If not completed, it is determined in step S413 whether the code buffer 116 is full, and if full, the step S4 is performed.
At 14, the code data stored in the code buffer 116
Transfer to HD117. That is, steps S412 to S414 are repeated until the encoding for one page is completed, and when the encoding for one page is completed, the process proceeds to step S419, after the encoded data stored in the encoding buffer 116 is transferred to the HD 117, The process ends.

If the determination result is color, the color encoding unit 115 starts encoding in step S415, and it is determined in step S416 whether encoding for one page has been completed, and the encoding must be completed. For example, in step S417, it is determined whether or not the code buffer 116 is full, and if full, the code data stored in the code buffer 116 is transferred to the HD 117 in step S418. That is, steps S416 to S418 are repeated until the encoding of one page is completed, and when the encoding of one page is completed, the process proceeds to step S419, and the encoded data stored in the encoding buffer 116 is stored.
After transferring to the HD 117, the process ends.

The code data stored in the HD 117 is the CCU
118 is transmitted to the other party via the line 119. The transmitted code data is normally deleted from the HD 117. However, when the color / monochrome automatic switching transmission is performed in the facsimile apparatus having the configuration shown in FIG. 1, even if the paper on which the document is recorded is other than white, it is determined to be color, and although it is desired to transmit the monochrome image, It may be sent as a color image. Examples for solving the above problems will be described below.

FIG. 5 is a block diagram showing a configuration example of a facsimile apparatus equipped with an image processing apparatus according to an embodiment of the present invention. In the figure, the same components as those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.
In FIG. 5, reference numeral 104 denotes a black pixel determination unit, which is a γ conversion unit 10
RGB data output from 3 is converted to YIQ by matrix conversion.
The pixel is converted into data, and a pixel whose Y data is less than or equal to a predetermined threshold and whose absolute values of I data and Q data are less than or equal to a predetermined threshold is determined as a black pixel.

Reference numeral 105 denotes an average value calculation section, which is a black pixel discrimination section 1
Based on the determination result of 04, the average value of pixels other than black in the RGB data output from the γ conversion unit 103 is calculated. 1
A user memory 06 stores the average value calculated by the average value calculation unit 105. A subtracter 107 is an average value calculated by the average value calculation unit 105 from the RGB data output from the γ conversion unit 103 or an average value read from the user memory 106 based on the determination result of the black pixel determination unit 104. Subtract. The result of this subtraction is input to the color / monochrome discriminating unit 108 to discriminate whether the original image is color or monochrome.

6A and 6B are operation parts 121 shown in FIG.
It is a figure which shows an example of the operation panel of. 2A and 2B are denoted by the same reference numerals and detailed description thereof will be omitted. In FIGS. 6A and 6B, reference numeral 229 denotes a background processing selection key for performing no background processing in the color / monochrome automatic switching transmission, performing background processing by prescan, or performing background processing using registered data. One of them is selected.

Reference numeral 230 is a background processing indicator for displaying the background processing method selected by the background processing selection key 229. FIG. 7 is a flowchart showing an example of the background registration procedure, which is executed by the control unit 120 when the background registration is selected by the background processing selection key 229. When the registration is completed, the background processing mode returns to the previous mode.

First, in step S301, selection /
Parameters such as the set document size, transmission image size, resolution, reading density, and binarization method are set in each image processing unit, and the image scanner 101 starts prescanning in step S302. Then, step S303.
Then, it waits until one block of image data of a predetermined size is read, and when the reading is completed, the calculation result of the average value calculation unit 105 is written to the user memory 106 in step S304. Specifically, the black pixel determining unit 104 determines a black pixel, the RGB data of the pixels determined to be other than the black pixel are cumulatively added by the average value calculating unit 105, and the average value is calculated when one block is read. After the calculation, a display as shown in FIG. 8 is displayed on the LCD 215. In response to this display, the user selects the one-touch dial key 201 or the numeric keypad 202.
When the registration name is input by and the set key 210 is pressed, the calculated average value of the RGB data of the background is written in the user memory 106, and the background registration is completed.

In this way, the background color of paper or the like excluding black pixels is extracted and stored, so that the background color according to the characteristics of the paper such as newspaper or recycled paper can be registered in advance. Since this pre-scan is for examining the background, it is sufficient to read the vicinity of the upper edge or the lower edge of the paper, etc., on which images are rarely recorded. It should be set to about the line.

FIG. 9 is a flow chart showing an example of the procedure for automatic color / monochrome switching transmission of this embodiment, showing the procedure for one page of the original. In FIG. 9, the same steps as those in FIG. 3 are designated by the same reference numerals, and detailed description thereof will be omitted. When the start key 213 or the accumulation key 212 is pressed, in step S401, parameters such as the selected / set document size, transmission image size, resolution, read density, and binarization method are set in each image processing unit, and step S401 is performed. S4
The process branches according to the background processing mode set in 02.

First, if no background processing is set, "00" is set in the subtraction register of the subtractor 107 in step S403, and then the process proceeds to step S408. Therefore, the color / monochrome discriminating unit 108 subtracts “00” from the RGB data output from the γ conversion unit 103, that is, the RGB data output from the γ conversion unit 103 remains unchanged, and the read image is color or monochrome. Determine whether. That is, the operation is the same as that of the image processing apparatus shown in FIG.

Next, when the background processing method based on the registered data is set, a display as shown in FIG. 10 is displayed on the LCD 215. In response to this display, the user presses the one-touch dial key 201 or the ten key 202 to
When the number of originals and the background registration data corresponding to each original are selected and the set key 210 is pressed, the selected background registration data is read out from the user memory 106 and set in the subtraction register of the subtractor 107. S4
Go to 08. Therefore, the color / monochrome discrimination unit 108
From the RGB data output from the conversion unit 103, the background registration data selected by the user, that is, the result of subtracting the average value of the background color, is used to determine whether the read image is color or black and white.

If the prescan is set, the image scanner 101 starts the prescan in step S405, waits for the image data of one block of a predetermined size to be read in step S406, and the reading is completed. Then, in step S407, the black pixel determination unit 10
The black pixel is discriminated by 4, and the RGB data of the pixels discriminated to be other than the black pixel are cumulatively added by the average value calculation unit 105, and when the reading of one block is completed, the average value is calculated. After the calculation result is set in the subtraction register of the subtractor 107, the process proceeds to step S408. Therefore, the color / monochrome discrimination unit 1
08 is the result of subtracting the average value of the background color of the transmission original from the RGB data output from the γ conversion unit 103,
Determine whether the scanned image is color or black and white.

As described above, according to this embodiment,
By registering the background color according to the characteristics of the paper or extracting the background color of the transmission original, for example, even though the original is black, the recording paper has a background other than white. It is possible to realize automatic color / black-and-white switching transmission that solves the problem of sending a color image even though it is desired to send it as a black-and-white image, because it is prevented from determining that the original.

[0043]

[Modification] In the embodiment described above, the page memory is
The example has been described in which the RGBK data is buffered in pixel units with a 4-bit configuration, but it is also possible to have a 16-bit or 8-bit configuration, or each RGBK is buffered in a memory of several bits. It is also possible.

Further, in the above-described embodiment, the example in which the dot sequential binary color encoding is used as the color encoding method has been described, but not limited to dot sequential, line sequential or area sequential is also possible. It is also possible to carry out the same with other coding schemes such as a multi-valued coding scheme using DCT without performing binarization. Further, in the above-described embodiment, an example in which RGBK data is stored in a page memory or the like has been described, but other color spaces such as YIQ and YCrCb may be used as long as they are orthogonal three-dimensional color spaces.

Further, in the above-described embodiment, an example of encoding the image data not subjected to the background processing has been described. However, the image data after the background processing is performed, that is, the image obtained by subtracting the average value of the background color. It is also possible to encode data, and a configuration example in that case is shown in FIG. That is, in FIG. 11, the output of the subtractor 107 is input to the black data generation unit 109. By doing so, each component after the black data generation unit 109 does not need to process the background color, the processing can be speeded up correspondingly, the generated code amount is small, and the communication time is shortened. There is also.

The present invention may be applied to a system composed of a plurality of devices or an apparatus composed of a single device. Further, it goes without saying that the present invention can be applied to the case where it is achieved by supplying a program to a system or an apparatus.

[0047]

As described above, according to claims 1, 5, 7,
According to the eleventh, fourteenth and sixteenth inventions, it is possible to correctly determine whether or not the original is color by extracting the background color information of the image data. In addition, claim 2,
According to the sixth, the twelfth and the fifteenth aspects, by storing the color information of the recording medium, it is possible to correctly determine whether or not the original is color.

According to the third and thirteenth aspects of the present invention, by extracting the color information of the recording medium, it is possible to correctly determine whether or not the original is color.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration example of a facsimile apparatus that performs color / monochrome automatic switching transmission.

2A is a diagram showing an example of an operation panel of the operation unit of FIG. 1. FIG.

2B is a diagram showing an example of an operation panel of the operation unit in FIG. 1. FIG.

FIG. 3 is a flowchart showing an example of a procedure of automatic color / monochrome switching transmission performed by the apparatus of FIG.

FIG. 4A is a timing chart illustrating the relationship between the image signal and the clock of the device of FIG.

FIG. 4B is a timing chart illustrating the relationship between the image signal and the clock of the device of FIG.

FIG. 4C is a timing chart illustrating the relationship between the image signal and the clock of the device of FIG. 1.

FIG. 5 is a block diagram showing a configuration example of a facsimile apparatus including the image processing apparatus according to the exemplary embodiment of the present invention.

6A is a diagram showing an example of an operation panel of the operation unit of FIG.

6B is a diagram showing an example of an operation panel of the operation unit of FIG.

FIG. 7 is a flowchart showing an example of a background registration procedure of this embodiment.

FIG. 8 is a diagram showing a display example of an LCD in background registration.

FIG. 9 is a flowchart showing a procedure example of color / monochrome automatic switching transmission according to the present embodiment.

FIG. 10 is a diagram showing a display example of an LCD when a background processing method based on registered data is set.

FIG. 11 is a diagram showing a configuration example of a facsimile apparatus having a configuration for encoding image data obtained by subtracting the average value of base colors.

[Explanation of symbols]

 104 Black Pixel Discrimination Unit 105 Average Value Calculation Unit 106 User Memory 107 Subtraction Unit 108 Color / Monochrome Discrimination Unit 109 Black Data Generation Unit 110 Pixel Density Conversion Unit 111 Binarization Unit 112 Serial-Parallel Conversion Unit 113 Page Memory 114 Black and White Encoding Section 115 color encoding section 120 control section 121 operation section 229 background processing selection key

Claims (16)

[Claims] 1. An extracting unit for extracting background color information of image data, a determining unit for determining whether or not a document of the image data is color based on the color information extracted by the extracting unit, and the determining unit. And an encoding unit that encodes the image data according to the determination result of 1. 2. Storage means for storing color information of at least one recording medium, determination means for determining whether or not a document of image data is color based on the color information read from the storage means, and the determination means. And an encoding unit that encodes the image data according to the determination result of 1. 3. Extraction means for extracting color information of a recording medium, storage means for storing at least one color information extracted by the extraction means, and image data of image data based on the color information read from the storage means. An image processing apparatus comprising: a determination unit that determines whether or not a document is color, and an encoding unit that encodes the image data according to a determination result of the determination unit. 4. The determination unit, a subtraction unit for subtracting the color information from the image data, a conversion unit for converting a color space of a subtraction result of the subtraction unit, and color component data output from the conversion unit. A detection unit that detects pixels whose absolute value exceeds a predetermined threshold value, and determines that the document is color when the number of pixels detected by the detection unit exceeds a predetermined threshold value. The image processing apparatus according to claim 1. 5. A discriminating means for discriminating black pixels of image data, a calculating means for calculating an average value of the image data excluding the black pixels discriminated by the discriminating means, and an average value calculated by the calculating means. Subtracting from the image data, determining means for determining whether the original of the image data is color based on the subtraction result of the subtracting means, and encoding the image data according to the determination result of the determining means. An image processing device, comprising: 6. A discriminating means for discriminating black pixels of image data, a calculating means for calculating an average value of the image data excluding the black pixels discriminated by the discriminating means, and a calculating means for calculating the average value from the image data. Subtraction means for subtracting the average value, storage means for storing at least one subtraction result of the subtraction means, selection means for selecting the subtraction result to be read from the storage means, and the storage means selected by the selection means A determination unit that determines whether the original of the image data is color based on the subtraction result read from the image data, and an encoding unit that encodes the image data according to the determination result of the determination unit. A characteristic image processing device. 7. A discriminating means for discriminating a black pixel of image data, a calculating means for calculating an average value of the image data excluding the black pixel discriminated by the discriminating means, and a calculating means for calculating the average value from the image data. Subtracting means for subtracting the average value, determining means for determining whether or not the original of the image data is color based on the subtraction result of the subtracting means, and the subtraction result is encoded according to the determination result of the determining means. An image processing device, comprising: 8. The determination unit includes a conversion unit that converts the color space of the subtraction result, and a detection unit that detects pixels in which the absolute value of the color component data output from the conversion unit exceeds a predetermined threshold value. The image processing apparatus according to any one of claims 5 to 7, further comprising: when the number of pixels detected by the detection unit exceeds a predetermined threshold, the document is determined to be in color. 9. The encoding means encodes in a color encoding method when the document is determined to be in color by the determining means, and performs a monochrome encoding method in other cases. The image processing apparatus according to any one of claims 1 to 8, which is characterized. 10. The determination unit includes a conversion unit that converts a color space of the image data, the brightness data output from the conversion unit is equal to or less than a predetermined threshold, and the color output from the conversion unit. The image processing apparatus according to claim 5, wherein a pixel whose absolute value of the component data is equal to or less than a predetermined threshold value is determined as a black pixel. 11. An extraction step of extracting background color information of image data, a determination step of determining whether or not a document of the image data is color based on the color information extracted in the extraction step, and the determination step. And an encoding step of encoding the image data according to the determination result of 1. 12. The color information of at least one recording medium is stored in the storage means, it is determined whether or not the original of the image data is color based on the color information read from the storage means, and according to the determination result. An image processing method, characterized in that the image data is encoded. 13. The extracted color information of the recording medium is stored in a storage unit, and whether or not the original of the image data is color based on the color information read from the storage unit that stores the color information of at least one recording medium. Is determined and the image data is encoded according to the determination result. 14. A determination process for determining a black pixel of image data, a calculation process for calculating an average value of the image data excluding the black pixels determined in the determination process, and an average value calculated in the calculation process. A subtraction step of subtracting from the image data, a determination step of determining whether or not the original of the image data is color based on the subtraction result of the subtraction step, and a code of the image data according to the determination result of the determination step. An image processing method, comprising: 15. A determination process for determining a black pixel of image data, a calculation process for calculating an average value of the image data excluding the black pixels determined in the determination process, and an average value calculated in the calculation process. A subtraction step of subtracting from the image data, a storage step of storing a subtraction result of the subtraction step in a storage means, a selection step of selecting a subtraction result to be read from the storage means for storing at least one subtraction result, A determination step of determining whether or not the original of the image data is color based on the subtraction result selected in the selection step and read from the storage means, and the image data is encoded according to the determination result of the determination step. An image processing method comprising: an encoding step. 16. A determination process for determining a black pixel of image data, a calculation process for calculating an average value of the image data excluding the black pixels determined in the determination process, and an average value calculated in the calculation process. Subtraction step for subtracting from the image data, a determination step for determining whether or not the original of the image data is color based on the subtraction result of the subtraction step, and the subtraction result is encoded according to the determination result of the determination step. An image processing method, comprising: