JP3020240B2 - Color identification circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] A color identification circuit for separating various colors from a color image signal read from a color original is described. A color separation (clustering) without using a fixed threshold when separating colors A plurality of color holding circuits for holding color information of a new color found first by reading a color original with a plurality of colors passed through filters having different spectral characteristics and identifying colors; Calculate the distance between each of the retained colors and other colors,
A plurality of judgment circuits for judging whether each color is the same,
A new color recognition circuit that collects the outputs of these determination circuits to determine whether the target color is a new color, and receives the output of the new color recognition circuit and controls the color holding circuit to hold the new color. A control circuit, receives an output from the determination circuit, and a signal indicating whether the identified color is a chromatic color or an achromatic color, inputs and encodes these signals, and outputs a color signal indicating the type of hue from the encoded result. is composed of an encoder for outputting a new color on the color holding circuit is configured such are successively stored remotely least twice the maximum allowable distance d ₀ which can be recognized as the same color.

The present invention relates to a color identification circuit for separating various colors from a color image signal read from a color original.

[Prior Art] In a banking business or the like, a character reading OCR (Optical Char-
acter Reader) is used. This type of character reading OCR has also been used for reading handwritten characters due to improvements in pattern recognition technology. In this type of apparatus, a character entry frame (also referred to as a format) of a target form (hereinafter referred to as a manuscript) is printed in a dropout color. The dropout color is a color having a hue and a density that can be clearly distinguished by human eyes but cannot be distinguished from the background color by the OCR sensor. If such a dropout color is used for the character entry frame, the character entry frame disappears from the image data read by the OCR, so that the character entry frame and the characters can be separated.

FIG. 6 is a diagram showing a configuration example of a conventional OCR reading unit. In the document 1, characters (A, B, C, D) surrounded by a character entry frame (format) 1a are written. In the example shown in the figure, character information is read line by line in the main scanning direction while moving the original 1 in the sub-scanning direction. One line of the image on the document 1 is condensed by the condensing lens 2, the filter 3 removes the dropout color, and then input to the CCD image sensor 4. The CCD image sensor 4 converts the input light into an electric signal and outputs the electric signal. This electric signal is amplified to a predetermined level by the following amplifier 5, and then A / A
It is converted to digital data by a D converter (not shown),
Character recognition processing and the like are performed on the digital data.

[Problem to be Solved by the Invention] In the conventional method, it is necessary to select the characteristics of the dropout color and the filter 3 according to the writing implement (pencil or ballpoint pen), and replace the filter 3 according to the color of the dropout color. There was a problem that had to be done.

Then, the present inventor invented a method of reading a slip in color and then separating characters and format by color identification,
We filed an application (Japanese Patent Application No. 63-220067, hereinafter referred to as the prior invention). In this method, a document such as a slip is read as a three-color image signal, and the hue, saturation, and luminance (hereinafter, H (Hue), S (Satur
ation), V (Value)), and after separating achromatic and chromatic colors by a predetermined threshold in saturation, the achromatic color is used for character recognition, and the chromatic color is a plurality of predetermined chromatic colors. It is output as a binary or multi-valued image of the number of colors with a threshold value. Character entry frame information composed of chromatic colors can be used for cutting out characters.

FIG. 7 shows the background, the characters, and the area where the character entry frame is located in HSV coordinates after the HSV conversion. That is, since the background and the characters are achromatic, they enter the inner cylindrical area in the HSV coordinates, and the color character entry frame becomes the chromatic color, so they enter the outer hollow cylindrical area. In the prior invention, utilizing this property after the HSV conversion, a threshold is first applied at S to separate the achromatic characters and background from the chromatic character entry frame. And
A threshold is applied to V from the separated achromatic color to distinguish the character from the background. On the other hand, for the chromatic color, a threshold value for dividing the hue of the representative color used in the slip is determined in advance as shown in FIG. 8, and the threshold value is identified as a multi-value image of a predetermined number of colors.

FIG. 9 is a configuration block diagram showing an embodiment of the invention of the prior application. On the manuscript 11, there is a character entry frame 11a and characters entered therein. The image processing unit includes an image reading unit 20 and a color identification unit 30. In the image reading unit 20, the original
The information read from 11 is the lens L1, L2, L3 and filter F
1, consisting of F2, F3 and image sensors CCD1, CCD2, CCD3
An image signal for three colors is read line by line using a system optical system. The read signals are output from the following amplifiers A1 and A, respectively.
A / D converters ADC1 and AD after being amplified to a predetermined level by A2 and A3
It is converted to digital data by C2 and ADC3. Then, the signals are output from the signal lines l1 to l3.

The color identification unit 30 receives the signals for these three colors,
The converter 31 separates the signals into H, S, and V signals and outputs the signals. Among these signals, the S signal is compared by a comparison circuit 32 with a threshold value Ts for separating achromatic and chromatic colors. The comparison circuit 32 includes, for example, S
If <Ts, it is regarded as an achromatic color and outputs “0”. If S ≧ Ts, it is regarded as a chromatic color and outputs “1”.

On the other hand, the V signal and the H signal are input to the comparison circuits 33 and 34, respectively. Threshold Tv inputted to the comparison circuit 33 of the achromatic, is intended to distinguish the character and background brightness (also referred to as brightness), the threshold T _H, which is input to the comparison circuit 34 to distinguish the color belongs to. Threshold T _H, as will be inferred from FIG. 8, it is not necessary character entry box to distinguish if one color. One threshold is used for two colors, and two thresholds are used for three colors. The threshold and the number n of the thresholds are determined in advance according to the number of colors used for the slip, such as five thresholds for six colors.

The comparison circuit 33 compares the input V signal information with a threshold value Tv, and if the V signal <Tv, outputs the signal as "1" as a character.
If signal ≧ Tv, “0” is output as the background. Further, this output signal is supplied to a multiplexer controlled by a comparison circuit 32.
The achromatic portion is output as it is by 35, but the chromatic character entry frame portion is forcibly selected and output as "0" input to the other side of the multiplexer 35. Therefore, the character entry frame portion is removed in the same manner as when reading using the dropout color. This multiplexer 35
Is provided to a subsequent character recognition unit (not shown).

Comparison circuit 34, the H signal information inputted is compared with a threshold T _H of the plurality n predetermined as described above, with multi-level and outputs the H signal to the n value. For example, when six colors are distinguished as shown in FIG. 3, each color is represented by six values as compared with threshold values T1 to T5. Next, the chromatic portion of this output signal is output as it is by the multiplexer 36 controlled by the comparison circuit 32, but “0” input to the other end of the multiplexer 36 is output in the achromatic character entry frame portion. Forced selection,
It is output as a signal having a total of seven values. The output of the multiplexer 36 is a character entry frame reference section (not shown) at the subsequent stage.
Given to.

In the above-mentioned prior invention, as shown in FIG. 8, a color to be identified is given in advance, and the number of thresholds is determined according to the number of colors. In this method, for example, the following problems occur. This will be described with reference to FIG.
The figure illustrates color separation using a fixed threshold. The horizontal axis is H
(Hue) and the vertical axis is frequency. In FIG. 11A, since the number of colors is two, a threshold value T as shown by a broken line is taken in the middle of the number to separate yellow and red. On the other hand, in (b), since the number of colors is three, _two thresholds T ₁ and T ₂ are set. However, in this example, blue is distributed just over the threshold T ₂ , and when separated by the threshold as it is, blue is divided into two different colors (blue smaller than binary T _{2 and} blue larger than T _2). )
This causes a problem that the components are separated.

As the number of colors increases, examples of such defects further increase. In the above example, the threshold and the margin of the threshold are set at equal intervals. However, if the color to be recognized is known in advance, the threshold can be moved accordingly. However, when it is desired to read several types of slips at once, it is troublesome to give color information for each slip one by one, and the efficiency is greatly reduced. In addition, the circuit becomes complicated, and it has been desired to solve the problem by some other method. As a solution, color separation by simple clustering can be considered.
There is a problem that processing time is required and the circuit configuration is complicated.

The present invention has been made in view of such a problem, and performs color separation for an arbitrary color by performing separation (clustering) by a set of colors without using a fixed threshold when separating colors. It is an object of the present invention to provide a color identification circuit capable of performing the following.

[Means for Solving the Problems] FIG. 1 is a principle block diagram of a main part of the present invention, and FIG. 2 is a diagram showing an example of the overall configuration of the present invention. In FIG. 2, the image reading section is omitted, but the configuration is the same as in FIG. The circuit of FIG. 2 is different from the circuit of FIG.
Is eliminated, and a clustering circuit 37 is provided instead. The output of the clustering circuit 37 is passed to the character entry frame reference section. Next, FIG. 1 showing a specific configuration example of the clustering circuit 37 will be described.

In FIG. 1, reference numeral 41 denotes a plurality of color holding circuits for holding color information of a new color found first, and 42 calculates a distance between each held color and another color, and determines whether each color is the same color. It is a plurality of determination circuits for determination. The n color holding circuits 41 and the judging circuits 42 are provided in accordance with the number n of colors. 43 is a new color recognition circuit that collects the outputs of these determination circuits 42 and determines whether the target color is a new color,
44 receives the output of the new color recognition circuit 43 and
A control circuit for controlling the 41 to hold a new color. Regarding the operation of the whole circuit using this circuit,
This is almost the same as the drawing, except that a clustering circuit 37 is provided instead of the comparison circuit 34 and the multiplexer 36 in FIG.

[Operation] The present invention does not use a fixed threshold value according to the number of colors to separate colors, but separates by a set of colors (clustering, C
lustering). In the present invention, the increase in the processing time due to the clustering requires only the processing time that is not different from the method using the fixed threshold value by devising a circuit that performs the processing in parallel. Moreover, the discrimination accuracy is superior to the fixed threshold method.

As shown in FIG. 3, when the hue Ha of a certain pixel is read, the distance to each class (set) is calculated and the classes are classified. In other words, when there are classes 1 to n now, Is calculated. Here, H ₁ ~Hn shows a different representative hue value each class.

Now, the maximum allowable distance can be recognized as the same color among the d ₁ -Dn (color to be identified, it is assumed that both are separated from each other 2d ₀ or more) d ₀ look smaller di. That is, it calculates which class it is close to. Calculation result to ensure that the target pixel if found class becomes d ₀ less belonging to the class i. Here, if any of d _{1 to} dn exceeds the maximum allowable distance d ₀ that can be recognized as the same color, a new class is generated for the pixel of interest. According to the present invention, the color distribution does not straddle the threshold value which is a problem with the conventional fixed threshold value, and the optimal threshold value is automatically obtained according to the number of colors, and color separation that matches human senses Can be performed.

The H signal in FIG. 2 is input to the control circuit 44, the color holding circuits 41, and the determination circuit 42 in FIG. The color holding circuit 41 and the determination circuit 42 are paired one by one, and are prepared for the number of colors to be identified and processed in parallel. Each color holding circuit 41 holds the first H value of each cluster (set) by a latch signal from the control circuit 44. The determination circuit 42 of each stage calculates the difference between the value of the color holding circuit 41 (the representative hue value of the color) and the newly input pixel, and the result is the predetermined maximum allowable distance for recognizing the same color. smaller compared with d ₀ is determined that the same color outputs "1", and outputs the to "0" determined a different color larger.

If the outputs of all the determination circuits 42 are “0”, the new color recognition circuit 43 determines that the input color is a new color that does not belong to any color, and notifies the control circuit 44 of that fact. Send a signal. Upon receiving this signal, the control circuit 44 supplies a latch signal to the color holding circuit 41 of the next stage to which the latch command has been sent before, and newly registers the color of the pixel of interest. As described above, according to the present invention, color separation can be performed on an arbitrary color by performing separation (clustering) using a set of colors without using a fixed threshold when separating colors. An identification circuit can be provided.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 4 is a block diagram showing an embodiment of a clustering circuit which is a part of the present invention. In the illustrated embodiment, a register is used as the color holding circuit 41, and the case where the number of colors is n = 4 is shown. G1 is provided with a number corresponding to the number of colors by AND gates that receive the control output of the control circuit 44 at one input thereof and the output of the determination circuit 42 at the other input. The AND gate G1 ANDs the control signal output from the control circuit 44 and the judgment circuit 42 of each stage according to the number of currently found classes (the number of colors), and acquires only necessary judgment results. It is for. For example, if only two colors are classified, the third and fourth determination results are unnecessary. That is, if it is currently classified into two colors,
The two control signals a ₁ and a ₂ from the top are “1”, and the remaining control signals a ₃ and a ₃
a ₄ becomes “0”.

G2 is a NOR gate receiving the output of each AND gate G1,
The output is given to the control circuit 44. Noah gate G2
When all the determination results of each stage are “0”, that is, it is determined that the color does not belong to any class, the output “1” is given to the control circuit 44 by the NOR gate G2 to newly register this color. To inform. These AND gate G1 and NOR gate G2 correspond to the new color recognition circuit 43 of FIG. An encoder 45 receives and encodes the output of each AND gate G1, and the output is provided to a character entry frame reference section (not shown) at the subsequent stage. In addition, the encoder 45
Is supplied with a control signal from the comparison circuit 32 (see FIG. 2). The operation of the circuit configured as described above will be described below.

The H signal output from the HSV conversion circuit 31 (see FIG. 2) enters a control circuit 44, a register 41, and a determination circuit 42. Initially, it does not matter what the initial value is in the register 41. Each determination circuit 42 calculates a difference between the initial value stored in the register 41 and the input H signal. At first, a meaningless determination result is output, but the output of the AND gate G1 is forcibly set to "0" by the control signal "0" from the control circuit 44.

Since the NOR gate G2 receives all "0" signals, its output becomes "1" and sends a signal to the control circuit 44 indicating that it is a new color. Upon receiving this signal, the control circuit 44 outputs a latch instruction to the first-stage register 41, and the first color signal H1 is latched. Here, the difference operation is performed again, and the output of the determination circuit 42 naturally becomes “1” (because both the signal and the input signal in the register 41 are H1).
Here, for the first time, “1000” (signals b ₁ , b ₂ , b ₃ ,
b ₄ ) is input.

FIG. 5 is a diagram showing an encoder logical expression. here,
Although the encoder input has 5 bits, the leftmost end is a control signal given from the comparison circuit 32. When this signal is “1”, it indicates a chromatic color, and when this signal is “0”, it indicates an achromatic color. The next four bits are b ₁ , b ₂ , b ₃ , and b _{4 in} that order. Encoder 4
Reference numeral 5 does not perform encoding when the control signal from the comparison circuit 32 is "0", but performs encoding only when it is "1", that is, only when it is a chromatic color. The encoded output is represented by 3 bits, and is encoded for b ₁ , b ₂ , b ₃ , b ₄ excluding the leftmost bit of the input. Here, b ₁ is LSB, b ₄ is a MSB.

NOR gate G when “1000” enters encoder 45
The output of 2 is "0" and no latch instruction to the next register is issued. Next, when the second H signal H2 enters, the distance calculation is performed by the determination circuit 42 in the same manner as the determination of H1, and the determination result is output. At this time, only the first-stage determination circuit 42 performs a meaningful operation. As a result of the judgment, H1
When the same color is determined, the output of the NOR gate G2 is "0" and the same operation is repeated, and "1000" is output to the encoder 45.

Here, when the determination circuit 42 determines that H2 is a different color from H1, the output of the first-stage determination circuit 42 becomes “0”, and as a result, the outputs of all the AND gates G1 become “0”. And the output of the NOR gate G2 becomes "1". Then, the control circuit 44
An instruction is issued to latch the second color H2 in the register 41.
Then, the calculation is performed again, and this time, the encoder 45
Is output as "0100". At this time, the output of the NOR gate G2 is "0". After this, the third color signal H3 comes in. The determination circuit 42 determines which of the two colors the third and subsequent pixels belong to. Hereinafter, all pixels are classified by class (color) by calculating the distance from all the pixels to the representative color of the class.

According to the present invention, new colors are determined in order from the input image. In that case, between the new colors,
As mentioned above, all colors to be identified
2d since it is ₀ which are more away (see FIG. 3), is not that new color separation can not go wrong. The value of the maximum allowable distance d ₀ can be changed,
Fine color separation is possible as needed.

[Effects of the Invention] As described above in detail, according to the present invention, an arbitrary color can be obtained by performing separation (clustering) by a set of colors without using a fixed threshold when separating colors. To provide a color identification circuit capable of performing color separation. The clustering method according to the present invention can obtain a processing speed equivalent to that of the conventional method of separating colors by a threshold value.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the principle of the main part of the present invention, FIG. 2 is a diagram showing an example of the overall configuration of the present invention, FIG. 3 is an explanatory diagram of color clustering, and FIG. FIG. 5 is a diagram showing an encoder logical expression, FIG. 6 is a diagram showing a configuration example of a conventional OCR reading unit, FIG. 7 is a diagram showing a color distribution in an HSV color system, FIG. 8 is a diagram showing the relationship between the hue distribution and the threshold for dividing the hue, FIG. 9 is a block diagram showing the configuration of an embodiment of the invention of the prior application, and FIG. . In FIG. 1, 41 is a color holding circuit, 42 is a judgment circuit, 43 is a new color recognition circuit, and 44 is a control circuit.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-62-200485 (JP, A) JP-A-61-25199 (JP, A) JP-A-57-189278 (JP, A) JP-A 63-200278 254039 (JP, A) JP-A-63-64479 (JP, A) JP-A-63-262965 (JP, A) JP-A-62-296279 (JP, A) (58) Fields investigated (Int. ⁷ , DB name) G06F 15/62 H04N 1/40 G06K 9/20

Claims (1)

(57) [Claims] A circuit for identifying a color by reading a color original with a plurality of colors passed through filters having different spectral characteristics, comprising: a plurality of color holding circuits for holding color information of a new color found first; A plurality of determination circuits for calculating the distance between each color and the other colors and determining whether or not the colors are the same, and a new color recognition for determining whether or not the target color is a new color by combining outputs of the determination circuits A control circuit that receives an output of the new color recognition circuit and controls the color holding circuit to hold a new color; and an output from the determination circuit and determines whether the identified color is a chromatic color or an achromatic color. And an encoder that receives and encodes these signals, and outputs a color signal indicating the type of hue from the encoded result. The color holding circuit recognizes that the new color is the same color. The maximum allowable distance that
color identification circuit configured to are successively stored away more than twice the d _0.