JP3200398B2 - Image processing apparatus and method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects the background color of a document image using a multidimensional table, and determines the monochrome / color of the document image based on the detection result.

[0002]

2. Description of the Related Art Conventionally, in a color copying apparatus, it is automatically determined whether a read original is a black-and-white original or a color original. When the original is a black-and-white original, a black single-color copy is executed. A technique for executing copying using four colors is known. As a result, the copy time can be reduced and the cost can be eliminated.

[0003]

However, the above conventional example has the following problems. That is, if the background of a document such as a document using color paper or yellowish recycled paper has a uniform tint, the information portion such as a character or a pattern is a single black color. However, there is a problem in that the original is also determined to be a color original and an unnecessary portion of the background of the original is reproduced.

SUMMARY OF THE INVENTION It is an object of the present invention to detect the background color of a document with high accuracy, and to use the result to appropriately determine the monochrome / color of a document image.

[0005]

[0006]

In order to achieve the above object, the present invention has the following arrangement.

According to a first aspect of the present invention, there is provided an input means for inputting image data representing a document image and comprising a plurality of color components, and each of the plurality of color components based on the image data. Detecting means for detecting the background color of the original image from the frequency distribution generated by using the multidimensional table, and excluding the detected background color data from the black / white / color determination target colors of the original image. A determination unit for determining whether the original image is black and white or color.

According to a second aspect of the present invention, there is provided an image processing apparatus comprising: inputting image data representing a document image and comprising a plurality of color components, and multiplying each of the plurality of color components on an axis based on the image data; The background color of the original image is detected from the frequency distribution generated by using the dimension table, and the detected background color data is excluded from the black / white / color determination target color of the original image, and the black and white of the original image is determined. / Color determination.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a color image processing apparatus according to the present invention will be specifically described below with reference to the drawings.

In the description, M represents magenta, C represents cyan, Y represents yellow, Bk represents black, R represents red, G represents green, B represents blue, 4C represents full color, 3C represents full color, and 3C represents full color. Abbreviated.

(First Embodiment) FIG. 2 shows an overall configuration diagram of a digital full-color electrophotographic copying machine to which the present invention is applied.

An image scanner 201 reads an original and performs digital image signal processing. Reference numeral 202 denotes a printer unit which prints out an image corresponding to the original image read by the image scanner unit 201 on a sheet in full color. 400 for both scanner and printer
It has a resolution of dpi.

In the image scanner section 201, 20
Reference numeral 0 denotes a mirror pressure plate, and a platen glass (hereinafter, platen) 2
The document 204 on the document 03 is irradiated by a lamp 205, guided to mirrors 206, 207, and 208, forms an image on a three-line sensor (CCD) 210 by a lens 209, and has full-color information red (R) and green (G). , Blue (B) component to the image signal processing unit 211.
The CCD has 5000 pixels for each color. 205 and 206 are speeds V, and 207 and 208 are speeds 1
The entire surface of the original is scanned by mechanically moving the line sensor at / 2V in a direction perpendicular to the electrical scanning direction of the line sensor.
The image signal processing unit 211 electrically processes the read image signal to decompose it into magenta (M), cyan (C), yellow (Y), and black (Bk) components. M, C, Y,
One component of Bk is sent to the printer unit 202, and one full color print is performed by a total of four document scans.

The M, C, Y, and Bk image signals sent from the image scanner unit 201 in a frame-sequential manner are sent to a laser driver 212. Laser driver 212
Drives the semiconductor laser 213 in accordance with the image signal. The laser beam scans on the photosensitive drum 217 via the polygon mirror 214, the f-θ lens 215, and the mirror 216.

Reference numeral 218 denotes a rotary developing unit, which includes a magenta developing unit 219 and a cyan developing unit 220. Yellow developing section 22
1. A black developing section 222, in which four developing units alternately contact the photosensitive drum 217 and develop an electrostatic latent image formed on the photosensitive drum 217 with toner.

Reference numeral 223 denotes a transfer drum.
4 or 225 is wound around the transfer drum, and the image developed on the photosensitive drum 217 is transferred to the sheet.

After the four colors of M, C, Y, and Bk are sequentially transferred in this manner, the sheet passes through the fixing unit 226 and is discharged.

FIG. 1 is a block diagram of a color copying apparatus to which the present invention is applied, and will be described below.

The CCD reading unit 101 includes a color sensor capable of independently obtaining analog color signals of R (red), G (green), and B (blue), an amplifier for amplifying a signal for each color, and 8 It has an A / D converter for converting to a bit digital signal.

The signals that have been subjected to shading correction for each color by the shading correction unit 102 are corrected for deviation between colors and between pixels by a shift memory unit 103, and are then subjected to a color determination unit 11 described later.
2 and sent to a LOG converter 104 that performs logarithmic correction for light density conversion.

The density signals Y (yellow), M (magenta), and C (cyan) output from the LOG converter 104 are input to the black generator 105. For example, the black signal Bk is output from Min (Y, M, C). Generated.

Further, the masking / UCR unit 106 corrects the filter characteristics and the toner density characteristics of the color sensor with respect to the Y, M, C, and Bk signals output from the black generation unit 105, and removes them. One to be developed out of
The color is selected.

Next, after the density conversion is performed by the density conversion unit 107 in accordance with the development characteristics of the printer and the operator's preference, the trimming processing unit 108 edits a desired section and then sends it to the printer unit to form an image. .

In a synchronization signal generation unit 109, a horizontal synchronization signal BD (beam detect) signal and a vertical synchronization signal ITOP synchronized with printing of each line sent from the printer are provided.
(Image top) A horizontal synchronization signal HSYNC or a pixel synchronization signal C used inside the image scanner based on the signal.
LK and the like are generated and sent to each processing unit and CPU.

The document position detector 110 detects the position and size of the document based on the green (G) signal after the shading correction. The scaling / transfer processing unit 111 controls the cycle and timing of writing and reading data to and from the shift memory to realize scaling and movement of an image.

The CPU unit 113 has a well-known I / O circuit, a timer circuit, an interrupt control circuit, a serial communication circuit, a ROM, a RAM, and the like, in addition to the microprocessor, and controls the above-described processing units. The CPU unit 113 includes a pulse motor 114 for driving the optical system, the document illumination lamp 11
5. Sensor 116 for detecting the position of the optical system, operation unit 1
17. Control the digitizer 118 for the coordinate position.

FIG. 3A shows the configuration of the color determination section (112 in FIG. 1), which will be described below.

The color determination section has two roles. The first role is to detect the background color, and the second role is to determine whether the document is chromatic or achromatic based on the detected information.

The R3, G3, and B3 corner signal components for a certain pixel read from the shift memory unit 103 are input to the background check circuits 320, 330, 340, and the background detection circuit 350, respectively.

The background detection circuit 350 can detect image data at a predetermined position as background color data. Details will be described later.

The background check circuits 320, 330, 340
Then, based on the background color data of the document obtained by the background detection circuit described above, it is checked whether or not the image signal is the background, and in the case of the background, the image signal is converted so as not to contribute as data for color determination. . Background check circuit Figure 4
Will be described later.

The background check circuits 320, 330, 340
Are input to the maximum value detection circuit 301 and the minimum value circuit 302, and MAX = ma
x (R4, G4, B4), MIN = min (R4, G
4, B4) are output. In the present embodiment, for each input of 8 bits for each of R, G, and B, outputs of 6 bits for each of MAX and MIN are obtained.

Next, both MAX and MIN are inputted as addresses of the lookup table LUT 303, and as a result, a 1-bit color determination signal IRO is obtained.

FIG. 3B shows the contents of the LUT 303.
In the two-dimensional space composed of the inputs MAX and MIN, the area A is determined to be achromatic and “0” is output, and the area B is determined to be chromatic and “1” is output. The determination signal IRO obtained in this manner is input as a clock of the counter 304.

The counter 340 has a horizontal synchronizing signal HSYN.
The number of chromatic color determination pixels of the determination signal IRO is reset in C and within a section permitted by the GATE signal output from the flip-flop 306 in one main scanning line. This count value is supplied to the CPU 11 via the latch 305.
3 reads.

The flip-flop 306 is set by a count-up signal of an ST counter (start bit counter) 309 and reset by a count-up signal of an EN counter (end bit counter) 310.
A count permission signal GATE for the counter 304 is generated. The ST counter 309 and the EN counter 310 count down the count values written in the latches 307 and 308 by the CPU, respectively.

As described above, the number of chromatic color determination pixels in an arbitrary section of each main scanning line can be counted.

FIG. 4 shows a background check circuit, which will be described below. Since all of 320, 330, and 340 in FIG. 3 have the same configuration, FIG. 4 illustrates the circuit 320 for the R signal as an example.

The image signal R3 is supplied to comparators 323, 3
24 and the selector 327. The upper limit value Rmax of the R component of the background color detected by the background detection circuit is set in the latch 321, and the lower limit value Rmin of the R component is set in the latch 322 by the CPU in advance. Therefore, when Rmin <R3 <Rmax, the comparison outputs of the comparators 323 and 324 both become “1”, and the AND of the AND of them is obtained.
5 also becomes “1”. The selector 327 outputs R3 as R4 when the SEL signal is “0”,
When "1", the contents of the latch 326, for example, "FF" (H
EX) is output as R4.

Similarly, Gmin <G3 <Gm for the remaining two background check circuits 330 (or 340).
G4 when ax (or Bmin <B3 <Bmax)
(Or B4) as "FF" (HEX),
At other times, G3 (or B3) is output.

As described above, in the background portion of the original, R
4, G4, and B4 are all "FF" (HEX), so that the area A, that is, the achromatic color is determined in the above-described FIG. 3B, and the chromatic color determination is performed even if the background is colored. Does not contribute to counting the number of pixels.

The means for detecting the background will be described below with reference to FIGS. In the first embodiment, a portion designated by an operator on a document is set as a background, and color information of the portion is detected.

FIG. 5 shows a state in which a document with a tint of the background is placed on a digitizer and the point S of the background is pointed by a pointing pen. This operation of the operator obtains the coordinates (Xs, Ys) of the point S. Where Xs
Is a pixel unit, Ys is a line unit, and both units are 1/40.
0 inches.

FIG. 6 shows the background detection circuit 350. The up counter 359 is a main scanning counter using the image clock CLK as a clock, and starts counting in synchronization with the horizontal synchronization signal HSYNC. The up counter 360 is a sub-scanning counter that uses the horizontal synchronization signal HSYNC as a clock, and outputs an S signal output from the CPU 113 at the sub-scanning start end of the document.
The counting is started by the TART signal.

The count outputs of these two counters are latched by comparators 355 and 356, respectively.
7 and 358, and when they match, the comparison output XLE or YLE becomes "1". Also, C
The PU previously sets “Xs” and “Ys” indicating the position of detecting the background color specified by the digitizer 118 in the latches 357 and 358 in advance. XLE, Y
When both LEs are “1”, the output LE of the AND gate 354 becomes “1”, and the image signals R3, G3,
B3 is stored in latches 351, 352, and 353, respectively. After scanning the original, the CPU determines from the contents of these three latches the colors Ro, Go, B of the portion designated as the background by the operator.
o is detected.

From the margin values Rm, Gm, and Bm determined empirically in advance, Rmax = Ro + Rm, Rmi
n = Ro−Rm, Gmax = Go + Gm, Gmin = G
o-Gm, Bmax = Bo + Bm, Bmin = Bo-B
m is defined and used as described in FIG.

In FIG. 6, latches 351 and 35 are provided.
The known smoothing circuits 361, 362, 3
By inserting 63, more stable detection of the background color is possible.

Further, in FIG. 6, sub-scanning counter related circuits 356, 358 and 360 and smoothing circuits 361 and 36 are shown.
An inexpensive detection circuit using only the circuit portion 364 excluding 2, 363 can be configured. In this case, after moving the optical system driven by the stepping motor 114 to an arbitrary sub-scanning position, the CPU uses a main scanning counter to
Any pixel in each main scan line can be sampled. Then, as shown in FIG. 7, the CPU calculates a weighted average value having an appropriate weight of, for example, 7 × 7 = 49 pixels centered on the target pixel (Xs, Ys) for each color by the CPU, and obtains the background color R
o, Go, and Bo can also be obtained.

As described above, when determining whether a document is a black-and-white document or a color document, unnecessary color copying can be prevented by excluding the background color of the document from the determination target. In other words, by providing a means for detecting and determining the background color of the document and its uniformity, it is possible to obtain an appropriate development color, paper, density,
Color and the like can be automatically selected.

(Second Embodiment) In the first embodiment, the background portion is designated by the operator. This is effective when there are many variations in the background color of the original, but a specific color paper or recycled paper is used. For a background color that is determined as in the case of using a copy output as a document, it takes time and effort to specify the background color, and the operability is not good. In the second embodiment, the operability is improved by easily specifying background color data frequently used as a document such as a reproduction paper copy.

FIG. 8 shows the operation unit according to the second embodiment, which will be described. 400 is a copy start key, 401 is a reset key for returning the copy mode to the standard state, 4
02 is a clear / stop key for resetting the number of copies to 1 or stopping the copy operation, 403 is a group of ten keys for inputting the number of copies and other data, 404 is a cassette key for selecting copy paper, and 405 is a copy density. A density key 406 for adjustment, a magnification key 406 for setting a copy magnification, and a display unit 410 for displaying settings such as the number of sheets, magnification, paper size, density, and the state of the apparatus. 707
Is a color mode key for selecting a color mode, and 411 is a display unit for displaying the selected state, and is a black single color copy for copying in a single black color regardless of the original, and M, Y, C, and K 4 regardless of the original. It has three modes: color copy for copying in full color, and ACS copy. A
CS is an abbreviation of “auto color selection”, and is a mode in which whether a document is black and white or color is determined, and either black monochromatic copy or color copy is automatically selected and executed.
Reference numeral 408 denotes a key for selecting the background color of the document, and 412 denotes a display unit for displaying the selected state. Here, three types of background colors can be selected. A key 409 is used to register these three background colors.

When executing the ACS copy, the operator selects the ACS mode with the key 407 and selects the background color of the original with the key 408, and then presses the copy start key 400. For example, "COL
"1" is a manuscript of a general white background, "COL2" is a manuscript of a yellowish recycled paper, and "COL3" is a pink colored paper which is often used in a specific meaning, for example, to call attention in a workplace. We use properly. And AC
A color to be excluded from the color determination target in the S copy is specified in advance.

FIG. 9 shows and describes the procedure for registering the background color. The user presses the key 409 (900) and selects "COL1" (901). A paper having a background color to be registered as “COL1”, for example, white copy paper is placed on the platen as “Original 1” (902), and the key 400 is pressed (90).
3). The optical system scans “document 1”, detects background color data, and stores areas Ro1, Go1, B1 on the nonvolatile RAM.
It is stored in o1 (904). The key 409 is pressed again (905), and "COL2" is selected (906). "C
A sheet having a background color to be registered as “OL2”, for example, a recycled sheet is placed as “document 2” (907), and the key 400
Is pressed (908), the background color data Ro2, Go
2. Detect and store Bo2 (909). Similarly, as “COL3”, for example, the color data of pink
It is detected and stored as o3, Go3, and Bo3, and the background color registration is completed.

FIG. 9 shows and describes the ACS copy procedure. Press the key 407 (920) to select "ACS mode".
Is selected (921). Press the key 408 (92
2), "COLj" (j = 1, 2, 3) is selected as the background color (923). Based on the background colors Roj, Goj, and Boj already detected and stored in the above-described registration procedure, as described in the first embodiment, the comparison values for setting in the background check circuits 320, 330, and 340. Rmax-j, Rmin-j, Gmax-
j, Gmin-j, Bmax-j, and Bmin-j are calculated and set (924, 925, 926). Key 40
By pressing 0 (927), a copy operation is performed (92).
8).

As described above, operability is improved by preparing a key in which the background color of a frequently used document is registered in advance.

The concept of the present invention is particularly effective when copying a plurality of originals using an automatic document feeder (ADF). As shown in FIG. 10, when a plurality of originals of various types are copied, all of the original copy is to be color-copied except for the original C. However, the ACS copy according to the present invention does not require a color copy. For the originals A, C, and E, it is possible to accurately execute a monochrome black copy, and the operator only needs to select the background color of the paper included in the original group with the key before starting the copy. .

When ACS is performed by using the ADE, the background check circuit 320 shown in FIG. 4 is modified into 320 'shown in FIG. The difference between the circuit of FIG. 11 and FIG. 4 is that the latch 32 is used to increase the background color to be checked by one.
1 ', 322' and comparators 323 ', 324', A
One set of ND circuits 325 'is added, and AND circuits 325 and 3
The output of 25 'is mutually operated by an OR circuit 328. In the example of FIG. 10, when at least one of the color of recycled paper and the color of pink paper is detected as the background color, the FF value set in the latch 326 is output. The point is to do so.

The background color selection key 408 of the operation unit may be used to register in advance the number of the original set in the ADF on which the background color original whose color copy is to be canceled is set.

Note that the background color to be registered is not limited to recycled paper and pink paper, and the number of registrations is not limited to the above example.

(Third Embodiment) In the first and second embodiments, the background color that the user does not want to be judged as "color" is specified in advance by the operator. , The background color is automatically detected.

FIG. 12 shows an embodiment of the background detection circuit 350 different from that of FIG. 6, and will be described below.

The three image signals R 3, G 3, B 3 are input to the calculation section 500. The calculation unit 500 calculates the distance S from the origin of the coordinates (R3, G3, B3) in the three-dimensional space of RGB as a reference for background determination, and latches the data.
Output to The standard S has a larger value as the document is brighter. The standard S can be arbitrarily defined, including S = αR3 + βG3 + γB3 (where α, β, and γ are appropriate coefficients). The output of the latch 501 is the comparator 50
2 and the latch 504 of the reference S one clock or more before
Is output to the selector 503 when the output of the latch 501 is large. As a result, a new norm S is sent to the latch 504. The comparator 50
The output of 2 is input as a clock of latches 509, 510 and 511 after synchronizing with an image clock in a gate 505. By continuing the above operation for one main scanning line, each of the RGB color components (Rs, Gs, B) that gives the maximum value of the standard S between them is supplied to the latches 509, 510, and 511.
s) is stored. The CPU 113 outputs a horizontal synchronization signal HSY.
The contents of these latches are read in synchronization with NC, and FIG.
The contents H [R of the addresses (Rs, Gs, Bs) of the three-dimensional table H configured on the RAM as schematically shown in FIG.
s, Gs, Bs] is incremented by one. When the above operation is completed for all the sub-scanning areas, a histogram indicating the frequency of the background color of the document has been generated. Therefore, maxH [Ri, Gj, Bk] (where 0 ≦ i, j, k
≤255) is stored in the RAM as background color data (Ro, Go, Bo) described in the first and second embodiments. Can be excluded.

By reducing the number of bits of Rs, Gs and Bs, the capacity of the table H can be suppressed to an appropriate size.

As described above, even if the background color is not designated by the operator in advance, by automatically detecting the background color, the optimum ACS copy can be performed without limitation on the number of controllable original background colors. Become.

The method of using the color judgment result for each pixel may be, for example, black and white when all the pixels constituting the document are achromatic, and a predetermined number (predetermined ratio) of all the pixels.
Even if the following chromatic pixels exist, the pixels may be determined to be black and white. Further, sub-sampling (decimation) may be performed to determine chromaticity / achromaticity, for example, every four pixels.

The printer is not limited to the laser beam printer described above, but may be any printer capable of color output, such as an ink jet printer, a thermal printer, or a dot printer.

By providing a device for transmission and reception in front of the printer, the present invention can be applied to a color facsimile machine.

As described above, according to the above-described embodiment of the present invention, the monochrome / color of the original is automatically determined, and a monochrome black copy is performed for a monochrome original, and a color copy is performed for a color original. In a color copying apparatus, by providing a means capable of designating the background color of a document in advance and a means capable of excluding the designated color from black / white / color determination targets, for example, a copy on a tinted recycled paper or a colored paper is provided. Useless color copying can be prevented even when the output is a document. Furthermore, operability can be improved by providing means such as a key capable of registering the background color. Further, by providing a means for automatically detecting the background color, it is possible to handle more types of documents.

[0069]

According to the present invention, the background color of a document image is detected with high precision by detecting the background color of a document image from a frequency distribution generated using a multidimensional table having each of the plurality of color components as an axis. By detecting and excluding the detected background color data from the black / white / color determination target color of the document image, the monochrome / color determination of the document image can be favorably performed.

[0070]

[Brief description of the drawings]

FIG. 1 is a block diagram of an image processing circuit.

FIG. 2 is a sectional view of a color copying apparatus.

FIG. 3 is a block diagram of a color determination circuit.

FIG. 4 is a block diagram of a background check circuit.

FIG. 5 is an operation explanatory view.

FIG. 6 is a block diagram of a background color detection circuit.

FIG. 7 is an explanatory diagram of background color detection.

FIG. 8 is an operation display unit.

FIG. 9 is an explanatory flowchart of the second embodiment.

FIG. 10 is an explanatory diagram of the second embodiment.

FIG. 11 is a block diagram of a background check circuit according to the second embodiment;

FIG. 12 is a block diagram of a background color automatic detection circuit.

FIG. 13 is an explanatory diagram of a histogram.

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04N 1/40-1/409 H04N 1/46-1/64

Claims (2)

(57) [Claims] An input means for inputting image data composed of a plurality of color components indicating an original image, and a multi-dimensional table having each of the plurality of color components as an axis based on the image data. Detecting means for detecting the background color of the document image from the generated frequency distribution; and excluding the detected background color data from the black / white / color determination target color of the document image, An image processing apparatus comprising: a determination unit configured to perform determination of (1). 2. An image data comprising a plurality of color components representing an original image is input, and is generated based on the image data using a multi-dimensional table having each of the plurality of color components as an axis. Detecting the background color of the original image from the frequency distribution, excluding the detected background color data from the target color of black / white / color of the original image, and performing black / white / color determination of the original image. Characteristic image processing method.