KR20060095203A - Display device and method for driving the same - Google Patents

Abstract

Disclosed are a display device and a driving method thereof for improving display quality of a moving image. The timing controller changes the color reference grayscale data stored in advance according to the gray level distribution map of the input raw data, and converts the raw data into grayscale data based on the changed color reference grayscale data. The data driver converts the grayscale data into an analog data voltage and outputs the grayscale data to the display panel. The gate driver outputs a gate signal to the display panel under control of the timing controller. Accordingly, the display quality of the video can be improved by changing each color reference gray scale data adaptively to the input raw data.

Reference tone data, display quality, histogram analysis

Description

DISPLAY DEVICE AND METHOD FOR DRIVING THE SAME}

1 is a schematic block diagram of a display device according to an exemplary embodiment of the present invention.

FIG. 2 is a detailed block diagram of the timing controller shown in FIG. 1.

FIG. 3 is a detailed block diagram illustrating an operation of an R, G, and B gray scale changing unit of FIG. 2.

4 is a detailed block diagram for describing an operation according to another exemplary embodiment of the R, G, and B gray scale changing unit of FIG. 2.

FIG. 5 is a detailed block diagram illustrating the data driver shown in FIG. 1.

FIG. 6 is a detailed block diagram illustrating the data driving chip of FIG. 5.

7 is a flowchart illustrating a method of driving a display device according to an exemplary embodiment of the present invention.

8A to 8D are diagrams for describing a method of driving the display device illustrated in FIG. 7.

9 is a detailed flowchart of an embodiment of step S420 shown in FIG. 7.

10 is a detailed flowchart of another embodiment of step S420 shown in FIG. 7.

<Description of the symbols for the main parts of the drawings>

110: timing controller 130: reference voltage generator

150: data driver 170: gate driver

190: display panel 210: control signal generator

230: data processing unit 231: data input unit

232; Storage unit 234: R, G, B gray scale changing unit

235: R, G, B gradation insertion section 236: R, G, B gradation table

237 data output unit

The present invention relates to a display device and a driving method thereof, and more particularly, to a display device and a driving method thereof for improving the display quality of a moving image.

In general, a liquid crystal display includes an array substrate, a counter substrate, and a liquid crystal material having refractive index anisotropy (Δn) injected between the two substrates, and light transmitted by adjusting the intensity of an electric field applied to the liquid crystal material. A display device for displaying a desired image signal by adjusting the amount of.

Such a liquid crystal display device is widely used not only as a display device of a computer but also as a television for implementing a moving picture.

Since the first liquid crystal display device was developed as a display device for displaying a still image, there is a problem in that display quality is degraded due to lack of brightness or contrast in displaying a moving image.

Accordingly, the technical problem of the present invention is to solve such a conventional problem, and an object of the present invention is to provide a display device for applying dynamic red (R), green (G), and blue (B) gamma curves in response to a video. To provide.

Another object of the present invention is to provide a method of driving the display device.

The display device according to the embodiment for realizing the object of the present invention includes a display panel, a timing controller, a data driver, and a gate driver. The display panel displays an image. The timing controller changes the color reference grayscale information stored in advance according to the gray level distribution map of the input raw data, and converts the raw data into grayscale data based on the changed color reference grayscale information. The data driver converts the grayscale data into an analog data voltage and outputs the data voltage to the display panel. The gate driver outputs a gate signal to the display panel under control of the timing controller.

Preferably, the gradation level distribution map is histogram analysis information, and each color reference tone adjustment report includes red reference tone information, green reference tone information, and blue reference tone information. In addition, each of the color reference tone adjustment reports may include cyan reference tone information, magenta reference tone information, and yellow reference tone information.

More preferably, the display device includes a storage unit for storing the color reference gray scale information.

The timing controller may include a gradation analyzer configured to analyze gradation levels of raw data of a predetermined unit and output a gradation level distribution map, a gradation changer that changes the respective color reference gradation information based on the gradation level distribution map, and A gradation inserting unit for generating respective gradation data corresponding to the entire gradation level based on each changed gradation reference information and the gradation data for storing the gradation data corresponding to the raw data. It includes a table part.

The gradation changing unit may include a first color gradation changing unit that changes first color reference gradation information based on the gradation level distribution chart, and a second color gradation changing unit that changes second color reference gradation information based on the gradation level distribution map. And a third color gradation changing unit for changing third color reference gradation information based on the gradation level distribution chart.

The gray scale changing unit changes the first color reference gray scale information based on the gray scale distribution map, and a second color changed by multiplying the changed first color reference gray scale information by the ratio between the first color and the second color. A first multiplier for outputting color reference grayscale information and a second multiplier for outputting modified third color reference grayscale information by multiplying the ratio of the first color and the third color by the changed first color reference data. Here, the first color reference system adjustment information is green reference tone information.

The storage unit stores a ratio between the first color and the second color and a ratio between the first color and the third color.

According to another aspect of the present invention, there is provided a method of driving a display device including a display panel in which a pixel portion is formed in an area defined by adjacent data wires and adjacent gate wires. Changing each of the previously stored color reference gradation information according to the input gradation level distribution map of the input raw data, converting the raw data into gradation data based on the changed color reference gradation information, and outputting the gradation data as analogues. Converting the data signal into a data signal and outputting the data signal to the data line; and outputting a gate signal for activating the pixel portion to the gate line.

The step of converting the raw data into gradation data and outputting the gradation level analysis information by analyzing the gradation level of the input raw data of the predetermined unit, and each stored color reference based on the gradation level analysis information Changing the gradation information, generating respective color gradation data corresponding to the entire gradation level based on the changed respective color reference gradation information, and using the respective color gradation data to correspond to the raw data. Outputting grayscale data.

The changing of the color reference gradation information may include changing the first color reference gradation information based on the gradation level analysis information and between the first color and the second color previously stored in the changed first color reference gradation information. Outputting the changed second color reference gradation information by multiplying the ratio and outputting the changed third color reference gradation information by multiplying the ratio of the first color and the third color previously stored in the changed first color reference gradation information; do.

According to such a display device and its driving method, the display quality of a moving image can be improved by changing each color reference gray scale information adaptively to the raw data.

Hereinafter, with reference to the accompanying drawings, it will be described in detail the present invention.

1 is a schematic block diagram of a display device according to an exemplary embodiment of the present invention.

Referring to FIG. 1, the display device includes a timing controller 110, a reference voltage generator 130, a data driver 150, a gate driver 170, and a display panel 190.

The timing controller 110 controls the overall operation of the display device based on the source control signal CONTL and the main clock signal MCLK input from an external device. Specifically, the raw control signal CONTL includes a horizontal synchronization signal HSYNC, a vertical synchronization signal VSYNC, and a data enable signal DE.

The timing controller 110 controls the data control signal 110b for controlling the data driver 150 and the gate control signal 110c for controlling the gate driver 170 based on the source control signal CONTL. Output

The timing controller 110 converts the input source data R, G, and B into gradation data 110a to which the changed reference gradation information is applied, and outputs the converted gradation data 110a to the data driver 150. In this case, the changed reference gray scale is a dynamic change of the predetermined reference gray scale information according to the histogram analysis of the raw data (R, G, B).

The raw data R, G, and B include red, green, and blue data, and the changed reference system adjustment information includes red, green, and blue reference gray scale information corresponding to the red, green, and blue data, respectively.

Accordingly, the timing controller 110 outputs the red, green, and blue gray data R1, G1, and B1 corresponding to the red, green, and blue raw data R, G, and B, respectively. Here, the case where the raw data includes red, green, and blue colors is taken as an example, but it is obvious that the data may include various colors supported by the system. For example, cyan, magenta, yellow and white.

For example, the reference voltage generator 130 generates six reference voltages V1, V2, .. V6, and transmits the reference voltages V1, V2, .. V6 to the data driver 150. Output The reference voltages V1, V2, ... V6 are used to convert digital grayscale data R1, G1, B1 into analog data voltages.

The data driver 150 uses the digital grayscale data R1, G1, and B1 based on the data control signal 110b and uses the reference voltages V1, V2,. The data voltage is converted into a data voltage and output to the data line DL of the display panel 190.

The gate driver 170 generates a gate signal based on the gate control signal 110c. The gate driver 170 outputs the gate signal to the gate line GL of the display panel 190.

The display panel 190 has an array substrate, an upper substrate, and a liquid crystal layer interposed between the substrates. The array substrate has a plurality of data lines DL and a plurality of gate lines GL intersecting the data lines DL, and includes a plurality of pixel portions defined by the data lines and gate lines. Have The pixel unit includes a switching element TFT, a liquid crystal capacitor CLC, and a storage capacitor CST. The gate electrode of the switching element TFT is connected to the gate line GL, the source electrode is connected to the data line DL, and the drain electrode is connected to the pixel electrode which is the first electrode of the liquid crystal capacitor CLC. . The storage capacitor CST is defined by the gate electrode and the pixel electrode.

The upper substrate has a color filter for expressing color at a position corresponding to the pixel portion, and has a common electrode which is a second electrode of the liquid crystal capacitor CLC. Common voltages VCOM and VST are applied to the common electrodes of the liquid crystal capacitor CLC and the storage capacitor CST.

FIG. 2 is a detailed block diagram of the timing controller shown in FIG. 1.

Referring to FIG. 2, the timing controller 110 includes a control signal generator 210 and a data processor 230. The control signal generator 210 controls the clock signal CLK, the data control signal CONTL-D, and the gate control to drive the display device based on the input source clock signal MCLK and the source control signal CONTL. Generate and output the signal CONTL-G.

The data processor 230 may include a data input unit 231, a storage unit 232, a histogram analyzer 233, an R, G, and B gray scale changing unit 234, an R, G, and B gray scale inserting unit 235, R, G, B grayscale table 236, and a data output unit 237.

The data input unit 231 receives raw data R, G, and B from an external device through a first interface method (eg, Low Voltage Differential Signal (LVDS)). For example, the data input unit 231 has an input terminal corresponding to the LVDS scheme, and receives the raw data R, G, and B transmitted through the LVDS scheme.

The storage unit 231 stores R reference gradation information, G reference gradation information, B reference gradation information, and weights for dynamically controlling the R, G, and B reference gradation information. The R, G, and B reference gray scales are information data on R, G, and B reference gray scales in digital form. For example, the R reference gradation coordinate information information (TAP POINT POSITION INFORMATION) for a predetermined gradation level sampled among all gradation levels, and the information data (TAP POINT GAMMA DATA) for the gradation voltage corresponding to the gradation level. Include.

The histogram analyzer 233 analyzes the gradation levels of the raw data R, G, and B by grouping the input raw data R, G, and B in predetermined units (for example, frame units). The histogram analysis unit 233 analyzes the distribution of the gradation level of the raw data by applying the TAP POINT POSITION INFORMATION and the weights 232a of the red, green, and blue colors. do. The red, green, and blue color weights are pre-stored in the storage unit 232.

For example, the raw data (R, G, B) of a dark screen has a high degree of distribution at a low gradation level, and the raw data (R, G, B) of a bright screen has a high degree of distribution at a high gradation level. The histogram analyzer 233 provides the analyzed histogram information 233a to the R, G, and B gray scale changing unit 234.

The R, G, B gray scale changing unit 234 changes the R, G, and B reference gray scale information 232b provided from the storage unit 232 based on the histogram analysis information 233a. The R, G, B gray scale changing unit 234 changes the R, G, and B reference gray scale information in consideration of preset weights. The R, G, B gray scale changing unit 234 outputs the changed R, G, and B reference gray scale information 235r, 235g, and 235g to the R, G, B gray scale inserting unit 235.

The R, G, and B gray scale inserting units 235 correspond to the entire gray level by interpolation using the changed R, G, and B reference gray scale information 235r, 235g, and 235g. Calculate the data. For example, the R, G, and B gray scale inserting unit 235 generates a total of 256 gray scale data using 10 changed reference gray scale information.

The R, G, B gradation table 236 is a lookup table type of R, G, and B gradation data corresponding to the entire R, G, B gradation levels generated by the R, G, B gradation insertion unit 235. Save as. In detail, each gray voltage corresponding to levels 0 to 255 is stored to be mapped one-to-one to digital data.

The raw data R, G, and B inputted into the R, G, and B grayscale tables 236 are converted into corresponding R, G, and B grayscale data 236r, 236g, and 236b and output.

The data output unit 237 is a second interface for transmitting the R, G, B grayscale data 236r, 236g, 236b output from the R, G, B grayscale table 236 to the data driver 150. A method (eg, Point to Point Differential Signaling (PPDS)) is converted and output.

In detail, the plurality of driving chips constituting the timing controller 110 and the data driver 150 are connected to each other in a one-to-one manner and use a PPDS scheme for transmitting data. Accordingly, the data output unit 237 outputs the R, G, and B grayscale data R1, G1, and B1 to the data driver 150 to correspond to the PPDS scheme.

FIG. 3 is a detailed block diagram illustrating an operation of an R, G, and B gray scale changing unit of FIG. 2.

2 and 3, the R, G, and B gray scale changing unit 234 includes an R gray changing unit 234-1, a G gray changing unit 234-2, and a B gray changing unit 234-3. ).

The R gray scale changing unit 234-1 changes the R reference gray scale information 232b_R provided from the storage unit 232 based on the histogram analysis information 233a provided from the histogram analyzing unit 233. That is, the R reference gradation information 235r is generated by applying a weight to the R reference gradation information 232b_R.

The G gradation changing unit 234-2 changes the G reference gradation information 232b_G provided from the storage unit 232 based on the histogram analysis information 233a provided from the histogram analysis unit 233. That is, the G reference gradation information 235g is generated by applying a weight to the G reference gradation information 232b_G.

The B gray scale changing unit 234-3 changes the B reference gray scale information 232b_B provided from the storage unit 232 based on the histogram analyzing information 233a provided from the histogram analyzing unit 233. That is, the B reference gradation information 235b is generated by applying a weight to the B reference gradation information 232b_B.

The reference gray level adjustment information is information data about a predetermined gray level and gray level voltages corresponding to the predetermined gray level among the gray level.

4 is a detailed block diagram for describing an operation according to another exemplary embodiment of the R, G, and B gray scale changing unit of FIG. 2.

2 and 4, the R, G, and B gray scale changing unit 330 includes a G gray scale changing unit 334, a first multiplier 336, and a second multiplier 337.

The G gradation changing unit 334 changes the G reference gradation information provided from the storage unit 332 based on the histogram analysis information 233a provided from the histogram analysis unit 233. That is, the G reference gradation information 235g is generated by applying a weight corresponding to the histogram analysis data to the G reference gradation information.

The first multiplier 336 multiplies the ratio data 332a of red and green previously stored in the storage unit 332 by the changed G reference gradation information 235g to output the changed R reference gradation information 235r.

The second multiplier 337 multiplies the ratio data 332b of blue and green previously stored in the storage unit 332 by the changed G reference gradation information 235g and outputs the changed B reference gradation information 235b.

Here, the storage unit 332 prestores the R reference gradation information and the weight 332_G corresponding to the R reference gradation information, the ratio data 332a of the red and green, and the ratio data 332b of the blue and green.

FIG. 5 is a detailed block diagram of the data driver shown in FIG. 1, and FIG. 6 is a detailed block diagram of the data driver chip of FIG. 5.

1 to 6, the data driver 150 includes a plurality of data driving chips CD1, CD2, .. CDm.

 The data driving chips CD1, CD2, .. CDm are connected to the timing controller 110 one-to-one by a PPDS interface. The timing controller 110 simultaneously outputs R, G, and B grayscale data R1, G1, and B1 to the data driving chips CD1, CD2, .. CDm. The reference voltage generator 130 simultaneously outputs reference voltages V1, V2,..., And V6 to the data driving chips CD1, CD2, .. CDm.

Each data driving chip 151 includes an interface unit 153, a digital analog converter 155, and a buffer unit 157.

The interface unit 153 receives R, G, and B grayscale data R1, G1, and B1 in channel units according to the PPDS scheme. The R, G, and B gray scale data R1, G1, and B1 are digital data.

The digital-to-analog converter 155 uses the reference voltages V1, V2,... V6 provided from the reference voltage generator 130 to generate the R, G, and B grayscale data R1, G1, and B1. Converts R, G, B data voltages (R, G2, B2) in analog form. Here, the initial three reference voltages V1, V2, and V3 among the six reference voltages are reference voltages for generating a data voltage having a first polarity with respect to the reference voltage, and the remaining three reference voltages V4, V5, and V6. ) Are reference voltages for generating a data voltage having a second polarity relative to the reference voltage.

The buffer unit 157 amplifies and outputs the R, G, and B data voltages output from the digital-to-analog converter 155 to a predetermined level.

That is, the R, G, and B data voltages R2, G2, and B2 output from the buffer unit 157 are output to the data line DL of the display panel 190.

7 is a flowchart illustrating a method of driving a display device according to an exemplary embodiment of the present invention. 8A to 8D are diagrams for describing a method of driving a display device. FIG. 8A is an input raw image, FIG. 8B is a histogram distribution diagram of raw data of FIG. 8A, and FIG. 8C is an R reference gradation information. And a graph of R reference gray scale information changed according to the histogram distribution diagram of FIG. 8B, and FIG. 8D is a diagram illustrating an image improved by the changed reference gray scale information of FIG. 8C.

2 and 7, the histogram analyzer 233 groups the input source data R, G, and B in units of frames, and the gradation level of the grouped source data R, G, and B. FIG. Analyze the distribution of (S410).

For example, when the raw data is a dark screen as shown in FIG. 8A, the histogram distribution of the raw data is higher in the low gray level than in the high gray level as shown in FIG. 8B.

The histogram analysis unit 233 analyzes the distribution of the gradation levels of the raw data by applying the TAP POINT POSITION INFORMATION and the weights 232a of the red, green, and blue colors. .

 The histogram analyzer 233 provides the histogram analysis information 233a to the R, G, and B gray scale changing unit 234. The R, G and B gray scale changing unit 234 changes the R, G and B reference gray scale information 232b provided from the storage unit 232 by applying a weight based on the histogram analysis information 233a ( S420).

For example, as shown in FIG. 8C, the R gray scale changing unit 234-1 uses the R reference gray scale information provided from the storage unit 232 based on the histogram analysis information 233a to have a large gray scale voltage having a low gray scale level. R reference gradation information is changed. Although not shown, the G and B gray scale changing unit changes the G and B reference gray scale information in the same manner.

The R, G, B gray scale changing unit 234 outputs the changed R, G, and B reference gray scale information 235r, 235g, and 235g to the R, G, B gray scale inserting unit 235.

The R, G, and B gray scale inserting units 235 respectively use the changed R, G, and B reference gray level information 235r, 235g, and 235g in an interpolation manner to correspond to the respective R, G, and B levels. Calculate B tone data (S430).

The R, G, B grayscale table 236 is a lookup table type of R, G, and B grayscale data corresponding to the entire R, G, B grayscale levels generated by the R, G, B grayscale inserting unit 235. Save as.

The raw data (R, G, B) input to the R, G, B grayscale table 236 is R, G, B grayscale data (236r, 236g, 236b) to which the changed R, G, and B reference grayscale information is applied. The converted and output (S440).

The R, G, and B grayscale data 236r, 236g, and 236b are transmitted to the data driver 150 in a predetermined interface scheme (PPDS).

The data driver 150 converts the R, G, and B grayscale data R1, G1, and B1 transmitted from the timing controller 110 into analog, R, G, and B data voltages R2, G2, and B2. (S450). The R, G, and B data voltages R2, G2, and B2 are output to the data lines DL of the display panel 190 (S460).

The gate driver 170 generates gate signals and outputs the gate signals to the gate lines GL of the display panel 190 under the control of the timing controller 110.

As a result, the display panel 190 displays an improved image as illustrated in FIG. 8D, in which the display quality D is improved compared to the raw image illustrated in FIG. 8A.

9 is a detailed flowchart of an embodiment of step S420 shown in FIG. 7.

3 and 9, the R gray scale changing unit 234-1 may display R reference gray scale information provided from the storage unit 232 based on the histogram analysis data 233a provided from the histogram analyzing unit 233. 232b-R) is changed (S421).

The G gradation changing unit 234-2 changes the G reference gradation information 232b-G provided from the storage unit 232 based on the histogram analysis data 233a provided from the histogram analysis unit 233 (S423). ).

The B gradation changing unit 234-1 changes the B reference gradation information 232b-B provided from the storage unit 232 based on the histogram analysis data 233a provided from the histogram analysis unit 233 (S425). ).

10 is a detailed flowchart of another embodiment of step S420 shown in FIG. 7.

4 and 10, the G gradation changing unit 334 changes the G reference gradation information provided from the storage unit 332 based on the histogram analysis data 233a provided from the histogram analysis unit 233. (S422).

The first multiplier 336 multiplies the pre-stored ratio data 332a of red and green by the changed G reference gradation information 235g and outputs the changed R reference gradation information 235r (S424).

The second multiplier 337 multiplies the pre-stored ratio data 332b of blue and green by the changed G reference gradation information 235g and outputs the changed B reference gradation information 235b (S426).

As described above, according to the present invention, the display quality of the video is improved by adaptively changing the red, green, and blue reference gray scale information corresponding to the input video including hardware for changing the red, green, and blue reference gray scale information. Can be improved.

In addition, only the hardware for changing the green reference gray scale information may be implemented, and the changed red reference gray scale information and the blue reference gray scale information may be obtained by applying the ratio between red and green and the ratio between blue and green to the changed green reference gray scale information, respectively. According to this method, the display quality of the video can be improved by implementing a simple hardware.

Although described above with reference to the embodiments, those skilled in the art can be variously modified and changed within the scope of the present invention without departing from the spirit and scope of the invention described in the claims below. I can understand.

Claims (13)

A display panel displaying an image; A timing controller for changing the color reference gray scale information according to the gray level distribution map of the input raw data and converting the raw data into gray scale data based on the changed color reference gray scale information; A data driver converting the grayscale data into an analog data voltage and outputting the grayscale data to the display panel; And And a gate driver configured to output a gate signal to the display panel under control of the timing controller. The display device of claim 1, wherein the gray level distribution is histogram analysis information. The display device according to claim 1, wherein each of the color reference tone adjustment beams includes red reference tone information, green reference tone information, and blue reference tone information. The display apparatus according to claim 1, wherein each of the color reference tone adjustment beams includes cyan reference tone information, magenta reference tone information, and yellow reference tone information. The display apparatus of claim 1, further comprising a storage unit for storing the color reference gray scale information. The method of claim 5, wherein the timing controller A gradation analyzer for analyzing a gradation level of the raw data of a predetermined unit and outputting a gradation level distribution map; A gradation changing unit for changing the respective color reference gradation information based on the gradation level distribution chart; A gradation inserting unit which generates respective gradation data corresponding to an entire gradation level based on the changed respective color reference gradation information; And And a gradation table unit for storing the respective gradation data and outputting gradation data corresponding to the raw data. The method of claim 6, wherein the tone change unit, A first color gray scale changing unit which changes first color reference gray scale information based on the gray level distribution; A second color gray scale changing unit which changes second color reference gray scale information based on the gray level distribution; And And a third color gradation changing unit which changes third color reference gradation information based on the gradation level distribution chart. The method of claim 6, wherein the tone change unit, A reference color gradation changing unit which changes first color reference gradation information based on the gradation level distribution chart; A first multiplier outputting the changed second color reference gray scale information by multiplying the changed first color reference gray scale information by the ratio between the first color and the second color; And And a second multiplier outputting the changed third color reference gray scale information by multiplying the changed first color reference data by the ratio between the first color and the third color. The display device according to claim 8, wherein the first color reference gauge is green reference tone information. The display device of claim 8, wherein the storage unit stores a ratio between the first color and the second color and a ratio between the first color and the third color. In a driving method of a display device including a display panel in which a pixel portion is formed in an area defined by data lines adjacent to each other and gate lines adjacent to each other, Changing each of the pre-stored color reference gray scale information according to the gray level distribution map of the raw data inputted from the outside, and converting the raw data into gray scale data based on the changed color reference gray scale information; Converting the grayscale data into an analog data signal and outputting the grayscale data to the data line; And And outputting a gate signal for activating the pixel portion to the gate wiring. The method of claim 11, wherein converting the raw data into grayscale data and outputting the grayscale data comprises: Analyzing the gray level of the input raw data of the predetermined unit and outputting gray level analysis information; Changing respective color reference gradation information previously stored based on the gradation level analysis information; Generating respective color gradation data corresponding to an entire gradation level based on the changed respective color reference gradation information; And And outputting grayscale data corresponding to the raw data using the respective color grayscale data. The method of claim 12, wherein the changing of the color reference gray scale information comprises: Changing first color reference gradation information based on the gradation level analysis information; Outputting the changed second color reference grayscale information by multiplying a ratio between the first color and the second color previously stored in the changed first color reference grayscale information; And And outputting the changed third color reference grayscale information by multiplying the ratio of the first color and the third color previously stored in the changed first color reference grayscale information.

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