KR20150080865A - Apparatus for interpolating color - Google Patents

Abstract

The present invention relates to a color interpolation apparatus which can improve reliability and continuity. The color interpolation apparatus comprises: an interpolation candidate calculation unit for calculating a directional interpolation candidate in respective upward, downward, left and right directions with respect to any G channel in an inputted Bayer color filter array pattern having a predetermined size; a unit for calculating gradient information in a channel for calculating gradient information in a channel with respect to the G channel in a left and right row, or in an upward and downward row corresponding to and around a directional interpolation candidate row; a unit for calculating gradient information between channels for calculating gradient information between channels with respect to the G channel in the left and right row or in the upward and downward row corresponding to and around the directional interpolation candidate row; a reliability calculation unit for calculating reliability of gradient information in a channel and reliability of gradient information between channels by calculating a weight value of gradient information in a channel as a standard deviation with regard to values of G channels in odd-numbered rows and calculating a gradient weight value between channels as an absolute value of a differential between an average of G channels in odd-numbered rows and an average of G channels in even-numbered rows; a fusion weight value calculation unit for calculating directional fusion weight values by using the gradient information in a channel, the gradient information between channels, the reliability of the gradient information in a channel and the reliability of the gradient information between channels; and a fusion unit for generating a G channel value by multiplying each directional interpolation candidate and each directional fusion weight value and adding thereof.

Description

[0001] APPARATUS FOR INTERPOLATING COLOR [0002]

The present invention relates to a color interpolation apparatus capable of improving reliability and continuity.

In a typical digital image processing apparatus, a single-chip image sensor using a charge coupled device (CCD) or a complementary metal semiconductor (CMOS) is used as a method for solving problems such as volume and hardware. In this case, a color filter array (CFA) is used in front of the image sensor to acquire color information. In general, a bayer CFA is used to acquire G channel information twice or more than R and B channels do. In the case of using CFA, an appropriate color interpolation method is required to acquire a color image because it has only one color information in one pixel. As a method of performing color interpolation, there are a method using a constant cross channel color difference and an edge directional color interpolation method.

In the dual edge directional color interpolation method, there is a method of adding inner channel gradient information and inter channel gradient information, and a method of selecting only one piece of information according to the result of dividing a pixel.

The conventional method of adding the intra-channel gradient information and the inter-channel gradient information is added without considering the reliability of the two types of gradient information, so that there is a disadvantage that the reliability of one of the two types of gradient information deteriorates.

In addition, the method of classifying an area into a flat area, an edge area, or a pattern area, and then performing edge directional color interpolation using only one of the two pieces of gradient information, I see a big loss.

Korean Patent Publication No. 2012-0040764

The technical problem to be solved by the present invention is to apply a weight calculated from the reliability of each gradient information in the case of intra-channel gradient information and inter-channel gradient information for determining the direction at the edge directional color interpolation, And a color interpolation apparatus capable of improving continuity.

According to an aspect of the present invention, there is provided a color interpolation apparatus including an interpolation candidate calculation unit for calculating interpolation candidates for an arbitrary G channel in an up / down / left / right direction in a Bayer color filter array pattern of a predetermined size, part; An in-channel gradient information calculation unit for calculating intra-channel gradient information for the G channel in a left / right column or an upper / lower column corresponding to the direction-based interpolation candidate column; An interchannel gradient information calculation unit for calculating interchannel gradient information for the G channel in a left / right column or a top / bottom column corresponding to the directionally interpolated candidate column; Gradient weights in the channel are calculated by the standard deviation of the odd column G channel values and the inter-channel gradient weight is calculated by the absolute value of the difference between the average of the odd column G channel values and the average of the even column G channel values, A reliability calculating unit for calculating the reliability of the gradient information and the reliability of the inter-channel gradient information; A convergence weight calculation unit for calculating a convergence weight for each direction by using reliability of the in-channel gradient information, the interchannel gradient information, the reliability of the in-channel gradient information, and the reliability of the interchannel gradient information; And a fusion unit for generating the G channel value by summing products of the interpolation candidates for each direction and the fusion weights for the respective directions.

In the present invention, the reliability calculation unit may calculate the intra-channel gradient weight by dividing the intra-channel gradient weight and the inter-channel gradient weight by the reliability calculation unit, and calculate the inter-channel gradient information Channel gradient weight is calculated by dividing the inter-channel gradient weight by the sum of the intra-channel gradient weight and the inter-channel gradient weight.

In the present invention, the weight calculation unit may multiply the product of the intra-channel gradient information reliability and the intra-channel gradient, the inter-channel gradient information reliability, and the inter-channel gradient, .

As described above, according to the present invention, by applying the weights calculated from the reliability of each gradient information at the time of convergence of the intra-channel gradient information and the inter-channel gradient information for determining the direction at the edge directional color interpolation, The continuity can be improved.

1 is a block diagram showing a configuration of a color interpolation apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating Bayer color filter array information according to an exemplary embodiment of FIG. 1. Referring to FIG.
FIGS. 3 to 5 are views showing a Bayer color filter array for explaining FIG. 1. FIG.

Brief Description of the Drawings The advantages and features of the present invention, and the manner of achieving them, will be apparent from and elucidated with reference to the embodiments described in conjunction with the accompanying drawings. It should be understood, however, that the present invention is not limited to the embodiments set forth herein, but may be embodied in many different forms and includes all conversions, equivalents, and alternatives falling within the spirit and scope of the present invention . BRIEF DESCRIPTION OF THE DRAWINGS The above and other aspects of the present invention will become more apparent by describing in detail preferred embodiments thereof with reference to the attached drawings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprises" or "having" and the like are used to specify that there is a feature, a number, a step, an operation, an element, a component or a combination thereof described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof. The terms first, second, etc. may be used to describe various elements, but the elements should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. .

1 is a block diagram showing a configuration of a color interpolation apparatus according to an embodiment of the present invention.

Referring to FIG. 1, the color interpolation apparatus 10 includes a G channel interpolator 100 and an R / B channel interpolator 200. In this embodiment, the G channel interpolating unit 100 includes an interpolation candidate calculating unit 110, an intra-channel gradient information calculating unit 120, an interchannel gradient information calculating unit 130, a reliability calculating unit 140, (150) and a fusion portion (160).

In this embodiment, a 7x7 Bayer color filter array pattern as shown in FIG. 2 may be used to implement directional edge color interpolation, and does not necessarily have to be a 7x7 Bayer color filter array pattern, A reduced Bayer color filter array pattern can be used. As shown in FIG. 2, in the Bayer color filter array pattern, since the G channel has relatively more information than the R / B channel, the G value in the R channel and the B channel is first restored. Also, in this embodiment, a method of restoring G25 with respect to an R25 pixel is described as an example, and other pixels are the same as those described below.

The interpolation candidate calculating unit 110 calculates interpolation candidates for the four directions of Top, Down, Left, and Right in order to restore G25 for R25 pixels using edge color interpolation by direction. Calculate candidates. The interpolation candidate calculating unit 110 may calculate an interpolation candidate for each direction with respect to G25 using Equation 1 described below.

In the equation (1), five pixels including the corresponding pixel R25 are used in the calculation of the interpolation candidate for each direction for G25. The interpolation candidate calculating unit 110 calculates an upward interpolation candidate value for G25 using five pixels of the upper columns G32, R25, G18, R11, and G04 including R25 as shown in FIG. 3 R25, G24, R25, G25, G25, G25, G25, G25, G25, G25, R25, G26, R27, and G28) are calculated using the five pixels of the right column (G24, R25, G26, R27, G28) And calculates a rightward interpolation candidate value.

The intra-channel gradient information calculating unit 120 calculates intra-channel gradient information for the G channel in the left / right column or the upper / lower column corresponding to the direction-based interpolation candidate column. The intra-channel gradient information calculation unit 120 calculates intra-channel gradient information (Inner Wt, Inner Wb, Inner Wl, Inner Wr) for the directionally interpolated candidate using Equation (2) described below.

4A, the in-channel gradient information calculation unit 120 includes an upward interpolation candidate sequence R25, G18, R11, and G04 except G32, and an upward interpolation candidate sequence (G24, B17, G10, and B03) and the right columns (G26, B19, G12, and B05) corresponding to the respective colors R25, G18, R11, and G04 And calculates the gradient information (Inner Wt) in the upward direction channel.

The in-channel gradient information calculating unit 120 includes the downward interpolation candidate rows R25, G32, R39 and G46 excluding G18 as shown in FIG. 4B, and the downward interpolation candidate rows R25, G32, R39, G40 and B47) and the difference between the channels of the same color in the right columns G26, B33, G40 and B47 are summed to obtain a gradient in the downward channel G25 for G25 Information (Inner Wd).

The in-channel gradient information calculation unit 120 includes leftward interpolation candidate rows R25, G24, R23 and G22 except for G26 as shown in FIG. 4C, and leftward interpolation candidate rows R25, G24, R23 and G22 G25, G16 and B15 and the lower columns G32, B31, G30 and B29, the difference between the channels of the same color is summed and the gradient information in the left channel ).

The in-channel gradient information calculation unit 120 includes rightward interpolation candidate rows R25, G26, R27 and G28 excluding G24 as shown in FIG. 4D, and right gradient interpolation candidate rows R25, G26, R27, G33 and G35 and the difference between the channels of the same color in the upper columns G18, B19, G20 and B21 and the lower columns G32, B33, G34 and B35 are summed and the gradient information in the right channel ).

The inter-channel gradient information calculation unit 130 calculates intra-channel gradient information for the G channel in the left / right column or the upper / lower column corresponding to the direction-based interpolation candidate column. Inter-channel gradient information calculation unit 130 calculates inter-channel gradient information (Inter Wt, Inter Wb, Inter Wl, and Inter Wr) for the directional interpolation candidates using Equation (3) described below.

According to Equation (3), the interchannel gradient information calculation unit 130 includes upward interpolation candidate rows R25, G18, R11, and G04 excluding G32 as shown in FIG. 5A, (G24, B17, G10, B03) and the right column (G26, B19, G12, B05) corresponding to the left channel (R25, G18, R11, G04) The sum of the value obtained by subtracting the sum of the upper and lower channels R10 and R24 from the sum of the upper and lower channels B10 and R12 A value obtained by subtracting the value obtained by subtracting the sum of the channel R11 from the sum of the upper and lower channels G04 and G18 and the sum of the upper and lower channels G12 and G26 from the channel B19, The value obtained by subtracting the sum of the upper and lower channels B05 / B19 from the channel G12 is added to calculate the upper interchannel gradient information (Inter Wt) for G25.

The inter-channel gradient information calculating unit 130 includes the downward interpolation candidate rows R25, G32, R39 and G46 excluding G18 as shown in FIG. 5B, and the downward interpolation candidate rows R25, G32, R39, The sum of the upper and lower channels G24 and G38 from the channel B31 to the left column G24, B31, G38 and B45 corresponding to the center G46 and the right column G26, B33, G40 and B47, A value obtained by subtracting the value obtained by subtracting the value obtained by subtracting the sum of the upper and lower channels B31 and B45 from the channel G38 and the sum of the upper and lower channels R25 and R39 from the channel G32, A value obtained by subtracting the sum of the upper and lower channels G32 and G46 from the channel R39 and the sum of the sum of the upper and lower channels G26 and G40 from the channel B33, Channel inter-gradient information (Inter Wd) for G25 by adding the value obtained by subtracting the sum of the lower channels (B33 / B47).

The interchannel gradient information calculation unit 130 includes leftward interpolation candidate rows R25, G24, R23 and G22 except for G26 as shown in FIG. 5C, and leftward interpolation candidate rows R25, G24, R23 and G22 ) Obtained by subtracting the sum of the left and right channels G16 / G18 from the channel B17 in the upper columns G18, B17, G16 and B15 and the lower columns G32, B31, G30 and B29, A value obtained by subtracting the sum of the sum of the left and right channels B15 and B17 from the channel G16 and the sum of the sum of the left and right channels R23 and R25 from the channel G24, A value obtained by subtracting the value obtained by subtracting the sum of the left and right channels G22 and G24 from the sum of the left and right channels G30 and G32 from the channel B31, B29 / B31) is added to the left interchannel gradient information (Inter Wl) for G25.

The inter-channel gradient information calculation unit 130 includes rightward interpolation candidate rows R25, G26, R27 and G28 excluding G24 as shown in FIG. 5D, and rightward interpolation candidate rows R25, G26, R27, The sum of the values obtained by subtracting the sum of the left and right channels G18 / G20 from the channel B19 in the upper columns G18, B19, G20 and B21 and the lower columns G32, B33, G34 and B35, A value obtained by subtracting the sum of the sum of the left and right channels B19 and B21 from the channel G20 and the sum of the sum of the left and right channels R25 and R27 from the channel G26, A value obtained by subtracting the value obtained by subtracting the sum of the left and right channels G26 and G28 from the value obtained by subtracting the sum of the left and right channels G32 and G34 from the value obtained by subtracting the sum of the left and right channels G26 and G28 from the channel B33, B33 / B35) is added to the right inter-channel gradient information (Inter Wr) for G25.

The reliability calculation unit 140 calculates the reliability of the intra-channel gradient information and the inter-channel gradient information. The reliability calculating unit 140 calculates an inner fusion weight of the in-channel gradient information and an inter fusion weight of the inter-channel gradient information using Equations (4) and (5) described below.

According to Equations (4) and (5), the reliability calculation unit 140 calculates the inner Fusion Weight_i in the channel at the time of calculating the inner Fusion Weight of the gradient information in the channel using the inner Fusion Weight_i ) And the inter-channel gradient weight (Inter Fusion Weight_i). Herein, the intra-channel gradient weight (i) can be calculated as a standard deviation of the odd column G channel values, and the inter-channel gradient weight (Inter Fusion Weight_i) can be calculated as the average of the odd column G channel values and Can be calculated as the absolute value of the difference with respect to the average. The reliability calculator 140 calculates inter-channel gradient weights (Inter Fusion Weight_i) and intra-channel gradient weights (Inter Fusion Weight_i) and inter-channel gradient weights (Inter Fusion Weight_i) at the time of calculating the Inter Fusion Weight of the interchannel gradient information Weight_i).

The weight calculating unit 150 calculates the weight of the gradation information in the channel based on the in-channel gradient information Inner Wt, Inner Wb, Inner Wl, Inner Wr, interchannel gradient information Inter Wt, Inter Wb, Inter Wl, Inter Wr, (Fusion WT, Fusion WD, Fusion WL, and Fusion WR) are calculated by using the inter-fusion weight (Inner Fusion Weight) and the inter-channel gradient information interfusion weight. The weight calculation unit 150 calculates Fusion WT, Fusion WD, Fusion WL, and Fusion WR by using Equations (6) and (7) described below.

According to Equations (6) and (7), it can be seen that the weight calculation unit 150 applies both intra-channel gradient reliability and inter-channel gradient reliability at the time of calculating the fusion weight for each direction.

The weight calculator 150 calculates the upward fusion weight by summing the product of the intra-channel gradient information reliability and the intra-channel gradient multiplication, the inter-channel gradient information reliability, and the inter-channel gradient. The weight calculator 150 calculates the upward convergence weight by summing the product of the intra-channel gradient information reliability and the downward channel gradient multiplication, the inter-channel gradient information reliability, and the downward interchannel gradient. The weight calculation unit 150 calculates the upward fusion weight by summing the product of the intra-channel gradient information reliability and the gradient in the left channel and the product of the inter-channel gradient information reliability and the left channel inter-channel gradient. The weight calculation unit 150 calculates the upward fusion weight by summing the product of the intra-channel gradient information reliability and the gradient in the right-direction channel, and the product of the inter-channel gradient information reliability and the inter-channel gradient.

The fusion unit 160 multiplies the interpolation candidate for each direction calculated by the interpolation candidate calculation unit 110 by the fusion weight for each direction calculated by the weight calculation unit 150 and then adds the resultant to generate a channel value of the final G25 . The fusion unit 160 interpolates the final G25 using Equation 8 described below.

The G channel interpolating unit 100 interpolates the edge directional G channel by applying weights calculated from the reliability of each gradient information when the intra-channel gradient information and inter-channel gradient information are merged.

The R / B channel interpolator 200 interpolates the R / B channel using the G channel interpolation result. In the case of R channel interpolation, the R value at the position of the B channel is interpolated and the R value located at the original G channel is interpolated. When interpolating the R value located on the B channel, first interpolate the R value located on the B channel in the Top-Right, Down-Right, Down-Left, Calculating a candidate, calculating a weight for each direction, and multiplying the product of the interpolation candidate for each direction and the weight for each direction. In interpolating the R value located in the G channel, interpolation candidates for the top, bottom, left, and right directions of the R value located in the G channel are calculated, The direction weighting value is obtained, and the sum of the products of the directionally interpolation candidate and the direction weighting value is calculated.

In the case of B channel interpolation, the B value at the position of the R channel is interpolated and the B value located at the original G channel is interpolated. The B channel interpolation is the same as the R channel interpolation, and a detailed description thereof will be omitted.

Since the reliability of the in-channel gradient information and the inter-channel gradient information is not taken into consideration in the conventional edge directional color interpolation method, there is a disadvantage that the reliability of one of the two gradient information is deteriorated when the reliability is low. It is also possible to classify an area into a flat area, an edge area, or a pattern area, and then perform edge directional color interpolation using only one of the two pieces of gradient information, . However, according to the present invention, by applying the weights calculated from the reliability of each gradient information in the fusion of the intra-channel gradient information and the inter-channel gradient information for determining the direction at the edge directional color interpolation, the reliability and continuity at the edge directional color interpolation are improved .

The various embodiments of the invention are not intended to limit the scope of the invention in any way. For brevity of description, descriptions of conventional electronic configurations, control systems, software, and other functional aspects of such systems may be omitted. Also, the connections or connection members of the lines between the components shown in the figures are illustrative of functional connections and / or physical or circuit connections and may be replaced or additionally provided with various functional connections, physical connections , Or circuit connections. Also, unless stated otherwise such as "essential "," importantly ", and the like, it may not be a necessary component for the practice of the present invention.

The use of the terms "above" and similar indication words in the specification of the present invention (particularly in the claims) may refer to both singular and plural. In addition, in the present invention, when a range is described, it includes the invention to which the individual values belonging to the above range are applied (unless there is contradiction thereto), and each individual value constituting the above range is described in the detailed description of the invention The same.

Unless there is explicitly stated or contrary to the description of the steps constituting the method according to the invention, the steps may be carried out in any suitable order. The present invention is not necessarily limited to the order of description of the above steps. The use of all examples or exemplary language (e.g., etc.) in this invention is for the purpose of describing the present invention only in detail and is not to be limited by the scope of the claims, It is not. It will also be appreciated by those skilled in the art that various modifications, combinations, and alterations may be made depending on design criteria and factors within the scope of the appended claims or equivalents thereof.

Accordingly, the spirit of the present invention should not be construed as being limited to the above-described embodiments, and all ranges that are equivalent to or equivalent to the claims of the present invention as well as the claims .

100: G channel interpolation section
110: interpolation candidate calculating unit
120: Gradient information calculation unit in the channel
130: Interchannel gradient information calculating unit
140:
150: Weight calculation unit
160: fusion unit
200: R / B channel interpolator

Claims (3)

An interpolation candidate calculating unit for calculating an interpolation candidate for an arbitrary G channel by an up / down / left / right direction in a Bayer color filter array pattern of a predetermined size to be inputted;
An in-channel gradient information calculation unit for calculating intra-channel gradient information for the G channel in a left / right column or an upper / lower column corresponding to the direction-based interpolation candidate column;
An interchannel gradient information calculation unit for calculating interchannel gradient information for the G channel in a left / right column or a top / bottom column corresponding to the directionally interpolated candidate column;
Gradient weights in the channel are calculated by the standard deviation of the odd column G channel values and the inter-channel gradient weight is calculated by the absolute value of the difference between the average of the odd column G channel values and the average of the even column G channel values, A reliability calculating unit for calculating the reliability of the gradient information and the reliability of the inter-channel gradient information;
A convergence weight calculation unit for calculating a convergence weight for each direction by using reliability of the in-channel gradient information, the interchannel gradient information, the reliability of the in-channel gradient information, and the reliability of the interchannel gradient information; And
And a convergence unit for generating the G channel value by summing products of the interpolation candidates for each direction and the fusion weights for the respective directions. The apparatus of claim 1, wherein the reliability calculator
The gradient weight in the channel is calculated by dividing the gradation weight in the channel by the sum of the gradient weight in the channel and the gradient weight between the channels,
Wherein the inter-channel gradient weight is calculated by dividing the inter-channel gradient weight by the sum of the intra-channel gradient weight and the inter-channel gradient weight at the time of calculating reliability of the inter-channel gradient information. The apparatus according to claim 1,
Wherein the directional fusion weight is calculated by summing products of a product of the intra-channel gradient information reliability and the intra-channel gradient, the inter-channel gradient information reliability, and the inter-channel gradient.

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