KR102479876B1 - Image processing device and image processing method - Google Patents

Abstract

The image processing device includes a calculation unit that calculates an on-pixel rate of input image data and calculates a final luminance of the display image based on a luminance change rate of the display image according to a change in the on-pixel rate; and an image converter configured to convert grayscale values included in the input image data based on the luminance change rate of the display image, the final luminance and the target luminance of the display image.

Description

Image processing device and image processing method {IMAGE PROCESSING DEVICE AND IMAGE PROCESSING METHOD}

The present invention relates to a display device, and more particularly, to an image processing device that processes and outputs input image data.

High dynamic range (HDR) (or HDR) technology analyzes contrast in detail to show natural images. For example, a display device using high dynamic range technology can achieve brightness of 1000 nit By expressing up to , the contrast can be expressed in detail. However, a general display device (or a display device using a low dynamic range (LDR, or LDR) technology) can display an image with a brightness of 300 nits or less. Accordingly, a general display device may not be able to display an image of a high diversity range (ie, an HDR image).

One object of the present invention is to provide an image processing device capable of displaying an image of a high diversity range in a display device of a low diversity range.

Another object of the present invention is to provide an image processing method capable of displaying an image of a high diversity range in a display device of a low diversity range.

In order to achieve one object of the present invention, an image processing apparatus according to embodiments of the present invention calculates an on-pixel rate of input image data, and based on a luminance change rate of a display image according to a change in the on-pixel rate, a calculator that calculates a final luminance of the displayed image; and an image conversion unit that converts a grayscale value included in the input image data based on the luminance change rate of the display image, the final luminance and the target luminance of the display image.

According to an embodiment, the calculator may include an analysis block that calculates the on-pixel rate of the input image data; and a modeling block for calculating the luminance change rate of the display image according to the on-pixel rate change, and calculating the final luminance of the display image based on the on-pixel rate and the luminance change rate of the display image. can

According to an embodiment, the modeling block may calculate the luminance change rate of the display image according to the change of the on-pixel rate based on test data having different on-pixel rates.

According to an embodiment, the luminance change rate may increase as the on-pixel ratio decreases.

According to an embodiment, the modeling block may calculate the final luminance based on the ideal luminance for the maximum grayscale value of the input image data, the on-pixel rate, and the luminance change rate.

According to an embodiment, the image conversion unit may include: a luminance determining block calculating a conversion ratio based on the final luminance and the target luminance; a mapping curve selection block that selects a first grayscale mapping curve from among a plurality of grayscale mapping curves based on the conversion ratio; and a mapping block that converts the grayscale value based on the first grayscale mapping curve selected from among the plurality of grayscale mapping curves.

According to an embodiment, the luminance determining block determines whether the final luminance is greater than the target luminance, and if the final luminance is less than the target luminance, determines the ratio of the target luminance based on the final luminance. The conversion ratio indicated can be calculated.

According to an embodiment, the plurality of grayscale mapping curves may respectively correspond to different conversion ratios.

According to an embodiment, the mapping block may reduce the on-pixel ratio of the display image based on the first grayscale mapping curve.

According to an embodiment, the mapping block may increase an average luminance of an object included in the display image based on the first grayscale mapping curve.

In order to achieve another object of the present invention, an image processing method according to example embodiments may be performed in a display device. The image processing method includes calculating an on-pixel rate of input image data; calculating a final luminance of the display image based on a luminance change rate of the display image according to a change in the on-pixel rate; and converting grayscale values included in the input image data based on the final luminance and target luminance of the display image.

According to an exemplary embodiment, the calculating of the final luminance of the display image may include: calculating the luminance change rate of the display image according to a change in the on-pixel ratio; and calculating the final luminance of the display image based on the on-pixel rate and the luminance change rate of the display image.

According to an exemplary embodiment, the calculating of the luminance change rate of the display image may include calculating the luminance change rate of the display image according to a change in the on-pixel rate based on test data having different on-pixel rates. can include

According to an embodiment, the luminance change rate may increase as the on-pixel ratio decreases.

According to an exemplary embodiment, the calculating of the final luminance of the display image may include calculating the final luminance based on an ideal luminance for a maximum grayscale value of the input image data, the on-pixel rate, and the luminance change rate. can include

According to an exemplary embodiment, the converting of the grayscale value included in the input image data may include calculating a conversion ratio based on the final luminance and the target luminance; selecting a first grayscale mapping curve from among a plurality of grayscale mapping curves based on the conversion ratio; and converting the grayscale value based on the first grayscale mapping curve selected from among the plurality of grayscale mapping curves.

According to an embodiment, the calculating of the conversion ratio may include determining whether the final luminance is greater than the target luminance; and calculating the conversion ratio representing the ratio of the target luminance to the final luminance when the final luminance is less than the target luminance.

According to an embodiment, the plurality of grayscale mapping curves may respectively correspond to different conversion ratios.

According to an embodiment, the converting of the grayscale value may include reducing the on-pixel ratio of the display image based on the first grayscale mapping curve.

According to an embodiment, the converting of the grayscale value may further include increasing an average luminance of objects included in the display image based on the first grayscale mapping curve.

An image processing device according to embodiments of the present invention calculates an on-pixel rate of input image data (eg, first data DATA1), and based on a luminance change rate of a display image according to a change rate of the on-pixel rate, The final luminance of the displayed image may be calculated, and the grayscale value may be converted so that the final luminance is equal to a target luminance (eg, luminance according to a high dynamic range (HDR) image). Accordingly, the image processing device may display a high dynamic range image even when a low dynamic range (LDR) technology is used.

Since the image processing method according to the embodiments of the present invention is performed in the image processing device, a display device using a low dynamic range (LDR) technology can display a high dynamic range image.

However, the effects of the present invention are not limited to the above effects, and may be expanded in various ways without departing from the spirit and scope of the present invention.

1 is a block diagram illustrating a display device according to example embodiments.
FIG. 2 is a diagram illustrating ideal luminance for each gray level of the display device of FIG. 1 .
FIG. 3 is a diagram illustrating an example of an image processing device included in the display device of FIG. 1 .
4A and 4B are diagrams illustrating an example of a luminance change rate according to a change in an on-pixel rate.
5A and 5B are diagrams illustrating examples of grayscale mapping curves used in the image processing device of FIG. 3 .
5C is a diagram illustrating an example of an object included in a display image.
6A and 6B are diagrams illustrating examples of actual luminance for each gray level of the display device of FIG. 1 .
7 is a flowchart illustrating an image processing method according to example embodiments.
8 is a flowchart illustrating an example of a step of calculating final luminance included in the method of FIG. 7 .
9 is a flowchart illustrating an example of a step of converting grayscale values included in the method of FIG. 7 .

Hereinafter, embodiments of the present invention will be described in more detail with reference to the accompanying drawings. The same or similar reference numerals are used for like elements in the drawings.

FIG. 1 is a block diagram illustrating a display device according to example embodiments, and FIG. 2 is a diagram illustrating abnormal luminance for each gray level of the display device of FIG. 1 .

Referring to FIG. 1 , a display device 100 may include a display panel 110, a scan driver 120, a data driver 130, a power supply 140, a timing controller 150, and an image processor 160. can The display device 100 may output an image based on image data (eg, first data DATA1) provided from the outside. For example, the display device 100 may be an organic light emitting display device.

The display panel 110 may include scan lines S1 to Sn, data lines D1 to Dm, and pixels PX (provided that n and m are integers of 2 or greater, respectively). The pixel PX may be disposed in an intersection area of the scan lines S1 to Sn and the data lines D1 to Dm. The pixel PX stores data signals (ie, data signals provided through data lines D1 to Dm) in response to scan signals (ie, scan signals provided through scan lines S1 to Sn), Light may be emitted based on the stored data signal.

Meanwhile, the driving current flowing through the pixel PX (or the driving current flowing through the driving transistor included in the pixel PX) may change according to a change in the driving current flowing to other pixels. For example, as the driving current flowing to other pixels decreases, the total driving current flowing through the entire display panel 110 decreases, and the resistance of the display panel 110 decreases (or increases) as the total driving current decreases (or increases). , IR drop) can be reduced (or increased). Accordingly, the driving current flowing through the pixel PX may relatively increase (or decrease). That is, the pixel luminance of the pixel PX may change (eg, increase or decrease) based on a load change of the display panel 110, and this phenomenon is defined as a load effect. can do.

The scan driver 120 may generate a scan signal based on the scan drive control signal SCS. The scan driving control signal SCS may be provided from the timing controller 150 to the scan driver 120 . The scan driving control signal SCS includes a start pulse and clock signals, and the scan driver 120 may include a shift register that sequentially generates scan signals based on the start pulse and clock signals.

The data driver 130 may generate a data signal in response to the data driving control signal DCS. Here, the data driving control signal DCS may be provided to the data driving unit 130 from the timing controller 140 . The data driver 130 may convert digital image data (eg, second data DATA3) into an analog data signal. The data driver 130 may generate a digital signal based on a preset grayscale voltage (or gamma voltage), and the grayscale voltage may be provided to the data driver 130 from a gamma circuit (not shown).

The power supply 140 may generate a driving voltage and supply the driving voltage to the display panel 110 (or the pixel PX). Here, the driving voltage is a power supply voltage required to drive the pixel PX, and for example, the driving voltage may include a first power supply voltage ELVDD and a second power supply voltage ELVSS. Here, the first power voltage ELVDD may be greater than the second power voltage ELVSS.

The timing controller 150 receives and displays image data (eg, second data DATA2) and input control signals (eg, horizontal sync signal, vertical sync signal, and clock signals) from an external device. Corrected image data (eg, third data DATA3) suitable for displaying an image of the panel 110 may be generated. Also, the timing controller 150 may control the scan driver 120 and the data driver 130 . The timing controller 150 may generate a scan driving control signal SCS and a data driving control signal DCS based on the input control signals.

The image processing unit 160 (or image processing device) analyzes input image data (eg, first data DATA1) provided from an external device to calculate the final luminance of the display image, and determines the final luminance of the display image. Converted image data (or output image data) (eg, second data DATA2) may be generated by converting the input image data DATA1 to be equal to the target luminance (or target luminance).

Here, the display image is an image displayed on the display device 100 based on the input image data, and the final luminance of the display image depends on the characteristics of the display panel 110 (or the characteristics of the material constituting the pixel PX). may be a luminance value (or a predicted luminance value) in which a luminance change rate of the displayed image according to the display image is reflected. For example, the luminance change rate of the display image may be set (or calculated) based on the change in the on-pixel rate of the input image data, and the abnormal luminance of the display image (eg, when the input image data is input, It may increase as the on-pixel ratio decreases based on the ideal luminance value displayed on the display device 100 . Here, an on-pixel ratio (OPR) may indicate a ratio of the number of pixels activated based on the input image data to the total number of pixels included in the display panel 110 . For example, the on-pixel ratio may be a ratio between the number of pixels displaying a specific grayscale on a portion of the display panel 110 and the total number of pixels included in the display panel 110 .

The image processing unit 160 has characteristics (or actual luminance) in which the final luminance (or actual luminance) of the display image changes according to the on-pixel rate of the input image data (or the on-pixel rate of the display panel 110 corresponding to the input image data). , road effect phenomenon), a display image may be displayed with a luminance value greater than the ideal luminance of the display panel 110 (eg, luminance according to the spec. of the display panel 110). In this case, the image processing unit 160 transmits a high diversity range image (or HDR image) (eg, an image having a maximum luminance of 1000 nits) to the low diversity range display device 100 (or LDR display device). (For example, a display device capable of displaying an image within a maximum luminance of 300 nits).

Referring to FIG. 2 , a first luminance curve 211 represents luminance for each gradation of an LDR image (or LDR display device), and a second luminance curve 212 represents luminance for each gradation of an HDR image (or HDR display device). brightness can be expressed. According to the first luminance curve 211, the LDR display device may display an image in a luminance range within the first luminance L1. Accordingly, when the LDR display device receives the HDR image according to the second luminance curve 212, the LDR display device can properly display the HDR image. For example, the LDR display device may display only images within a grayscale range smaller than the first grayscale value G1 of the HDR image. Also, even if the LDR display device scales the HDR image, the LDR display device may display the image only within a range within the first luminance L1. That is, the LDR display device may display an image in a range equal to or higher than the first luminance L1.

Meanwhile, a load effect may occur in an actual display device. The display device 100 (or the image processing device 160) according to embodiments of the present invention uses a load effect so that the final luminance of the display image is the target luminance (a luminance value greater than the ideal luminance). By converting the input image data to be equal to, even if the display device 100 uses the LDR technology, the HDR image can be displayed. The image processing unit 160 that converts input image data using a road effect will be described later with reference to FIGS. 3 to 6B.

Meanwhile, in FIG. 1 , the display device 100 is illustrated as having a separate image processor 160, but the display device 100 is not limited thereto. For example, the display device 100 may include a timing controller 150 that performs the function of the image processing unit 160 . For example, the image processor 160 may be included in the timing controller 150 and implemented.

FIG. 3 is a diagram illustrating an example of an image processing device included in the display device of FIG. 1 , FIGS. 4A and 4B are diagrams illustrating an example of a luminance change rate according to a change in on-pixel ratio, and FIGS. 5A and 5B is a diagram showing examples of grayscale mapping curves used in the image processing device of FIG. 3, and FIG. 5C is a diagram showing an example of an object included in a display image.

Referring to FIG. 3 , the image processing unit 160 (or image processing device) may include a calculation unit 310 and an image conversion unit 320 .

The calculation unit 310 calculates the on-pixel rate of the input image data (eg, the first data DATA1), and calculates the final luminance of the display image based on the luminance change rate of the display image according to the change in the on-pixel rate. can be calculated The image conversion unit 320 may convert grayscale values included in input image data based on the luminance change rate of the display image, the final luminance and the target luminance of the display image.

In embodiments, the calculator 310 may include an analysis block 311 and a modeling block 312 .

The analysis block 311 may calculate the on-pixel rate of the input image data (or the on-pixel rate of the display panel 110 based on the input image data). As described above, the on-pixel ratio may be a ratio between the number of pixels activated based on input image data and the total number of pixels included in the display panel 110 . For example, the analysis block 311 may extract or obtain display information of the input image data to be displayed on the display panel 110 for each frame of the input image data. Here, the display information may include a grayscale value (or brightness value) of a pixel that can be obtained from an RGB-type signal or a YCbCr-type signal constituting a display image. For example, the grayscale value may be expressed using 8-bit grayscale data and may be one of 256 grayscale values. The analysis block 311 may calculate an on-pixel ratio based on the grayscale value.

The modeling block 312 may calculate the final luminance of the display image. Here, the final luminance is a predicted luminance value of the display panel 110 estimated (or predicted) by the modeling block 312, and the modeling block 312 is a set value in which the material characteristics of the display panel 110 are reflected. It can be used to calculate the final luminance. For example, the final luminance may be calculated based on an ideal luminance corresponding to the maximum grayscale value of 255 and an on-pixel ratio for the maximum grayscale value.

In embodiments, the modeling block 312 calculates the luminance change rate of the displayed image according to the on-pixel rate change, and calculates the on-pixel rate (ie, the on-pixel rate calculated in the analysis block 311) and the luminance change rate (ie, the on-pixel rate). , the rate of change in luminance of the display image according to the change in the on-pixel rate), the final luminance of the display image may be calculated.

For example, the modeling block 312 may calculate a luminance change rate of a display image according to a change in an on-pixel rate based on test data (or test images) having different on-pixel rates. For example, the modeling block 312 may calculate the luminance change rate of the display image according to the on-pixel rate change using a preset calculation formula.

Referring to FIG. 4A , a luminance change rate according to a change in an on-pixel ratio is shown. Among the final luminances, the actual luminance REAL is a luminance value measured by a luminance measuring device (not shown) when a specific test image is provided to the display panel 110, and the model luminance MODEL is a luminance value predicted based on a specific calculation formula. It may be a luminance value.

Hereinafter, it is assumed that the display panel 110 displays a full white image (or the maximum grayscale value of 255) having a luminance of 300 nits or more, and the test images include the full white image (or the maximum grayscale value of 255). can do.

The test images may have different on-pixel ratios (OPRs) (eg, on-pixel ratios ranging from 25% to 100%), and the different test images may be displayed on the display panel 110 with different luminance. .

For example, the first test image may have an on-pixel ratio of 100%. In this case, the on-pixel ratio difference (D-DELTA) between the reference on-pixel ratio (eg, 100%) and the on-pixel ratio of the first test image is 0%, and the display panel 110 according to the first test image A first actual luminance of an image displayed on the image may be 304.40 nits. Accordingly, the first luminance increment (or the first luminance change rate) may be about 0%. That is, the ratio between the increment of the first actual luminance (eg, the luminance difference between the first actual luminance and the ideal luminance) to the ideal luminance according to the first test image (eg, 300 nits) may be about 0%. .

For example, the second test image may have an on-pixel ratio of 50%. In this case, the on-pixel rate difference (D-DELTA) is 50%, the second actual luminance according to the second test image is 349.70 nits, and the second luminance increment may be about 14.88%. For example, the third test image may have an on-pixel ratio of 25%. In this case, the third actual luminance according to the third test image may be 384.60 nits, and the third luminance increment may be 26.35%.

Referring to FIG. 4B , the luminance increase (or luminance change rate) according to the change in the on-pixel ratio (OPR) described with reference to FIG. 4A may appear along the luminance change curve. That is, the luminance change curve may represent the luminance change rate ΔL according to the change in the on-pixel ratio (OPR). As shown in FIG. 4B , the luminance change rate ΔL may increase as the on-pixel ratio (OPR) decreases. That is, the luminance change rate ΔL may increase or decrease in proportion to the on-pixel rate difference (eg, the on-pixel rate difference D-DELTA described above with reference to FIG. 4A).

Meanwhile, the modeling block 312 may model a luminance change curve through repetitive experiments. That is, the modeling block 312 may model the luminance change rate ΔL according to the on-pixel rate change through repetitive experiments.

In embodiments, the modeling block 312 may calculate a luminance change rate according to a change in on-pixel ratio based on Equation 1 below.

[Equation 1]

(1) DEL_LX = DELG_LX * VS

(2) M_LX = ((G/G_MAX)^GV + DELG_LX * VS) * 100

Here, DEL_LX is the luminance increase rate, DELG_LX is the on-pixel rate difference (D-DELTA) (eg, the difference between the reference on-pixel rate and the on-pixel rate of the input image data), and VS is the setting of the display panel 110. can be a value VS may vary according to material characteristics (or material characteristics) of the display panel 110 (or pixel PX), and may be, for example, 0.35. Also, M_LX may be the final luminance, G may be a grayscale value included in the input image data, and GV may be a gamma value (eg, gamma 2.2 to 2.2).

The final luminance (ie, the model luminance (MODEL)) and the luminance increment (ie, the modeled luminance change rate (MODEL(%))) calculated based on [Equation 1] may be as shown in FIG. 4A. That is, similar to the luminance increment obtained through repetitive experiments, the luminance change rate ΔL may increase as the on-pixel ratio (OPR) decreases.

In embodiments, the modeling block 312 calculates (or predicts) a luminance change rate of the input image data based on the on-pixel rate of the input image data, and calculates (or predicts) a final luminance of the display image based on the ideal luminance and the luminance change rate. It can be calculated (or predicted).

In one embodiment, the modeling block 312 may calculate the final luminance based on the ideal luminance, the on-pixel rate, and the luminance change rate for the maximum grayscale value of the input image data.

For example, the ideal grayscale for a 255 full white image, which is the maximum grayscale, is 300 nits (or 304.40 nits), the on-pixel ratio of the input image data calculated in the analysis block 311 is 50%, and the on-pixel ratio A luminance change rate according to change (eg, VS described with reference to Equation 1) may be 0.35. In this case, the modeling block 312 may calculate the final luminance of 357.67 nits for the input image data (eg, 304.40 * (1 + (100% - 50%) * 0.35)).

As described with reference to FIGS. 4A and 4B , the calculation unit 310 calculates the on-pixel rate of the input image data and the luminance change rate of the displayed image according to the on-pixel rate change, and calculates the ideal luminance, on-pixel rate, and The final luminance of the display image may be calculated based on the luminance change rate.

Referring back to FIG. 3 , the image converter 320 may include a luminance determining block 321 , a mapping curve selection block 322 and a mapping block 323 .

The luminance determining block 321 may calculate a conversion ratio based on the final luminance and the target luminance. Here, the target luminance is a luminance value to be displayed in the display device 100 based on the input image data, and may be greater than the maximum luminance specified in the specification of the display device 100 . Referring to FIG. 2 , for example, the final luminance is a luminance value predicted based on the ideal luminance on the first luminance curve 211 (eg, the luminance value of the LDR display device), and the target luminance is the second luminance. It may be a luminance value (eg, a luminance value of an HDR image) on the curve 212 . Meanwhile, the conversion ratio may indicate a ratio of target luminance to final luminance.

In an embodiment, the luminance determining block 321 may determine whether the final luminance is greater than the target luminance, and calculate a conversion ratio when the final luminance is less than the target luminance.

For example, as shown in FIG. 4A, the final luminance of input image data having an on-pixel ratio of 50% is about 357.67 nits, and the target luminance (the luminance value to be displayed based on the maximum grayscale value in the HDR display device) , or the maximum luminance value corresponding to the maximum grayscale of the HDR image) may be 500 nits. In this case, the luminance determining block 321 determines that the display device 100 cannot display the input image data with the target luminance, and calculates a conversion ratio for increasing the final luminance of the display device 100. there is. For example, the conversion ratio may be about 1.4 (i.e. 500 / 357.67).

As another example, the final luminance of input image data having an on-pixel ratio of 10% may be about 510 nits, and the target luminance may be 500 nits. In this case, the luminance determining block 321 determines that the display device 100 can display the input image data with the target luminance, and calculates a conversion ratio having a preset value (eg, 1). there is.

The mapping curve selection block 322 may select one grayscale mapping curve from among a plurality of grayscale mapping curves based on the conversion ratio. Here, the plurality of grayscale mapping curves correspond to different conversion ratios, and the selected one grayscale mapping curve may correspond to the conversion ratio calculated by the luminance determining block 321 .

Referring to FIG. 5A , the mapping curve selection block 322 may include first to fourth grayscale mapping curves 511 to 514 . Each of the first to fourth grayscale mapping curves 511 to 514 may represent a correlation between an input grayscale value and an output grayscale value. Here, the input grayscale value may be a grayscale value included in the input image data, and the output grayscale value may be a grayscale value included in the converted image data (or output image data) (eg, the second data DATA2).

For example, the first grayscale mapping curve 511 corresponds to a conversion ratio of 1, the second grayscale mapping curve 512 corresponds to a conversion ratio of 1.4, and the third grayscale mapping curve 513 corresponds to a conversion ratio of 2.0. , and the fourth grayscale mapping curve 514 may correspond to a conversion ratio of 3.0. Each of the grayscale mapping curves 511 to 514 may be previously set through repetitive experiments and previously stored in a memory device (not shown).

For example, the mapping curve selection block 322 may select the second grayscale mapping curve 512 (ie, the grayscale mapping curve corresponding to the conversion ratio of 1.4) based on the conversion ratio of 1.4.

Meanwhile, in FIG. 5A , the mapping curve selection block 322 is illustrated as including the first to fourth grayscale mapping curves 511 to 514, but the mapping curve selection block 322 is not limited thereto. For example, the mapping curve selection block 322 may include 3 or less or 5 or more grayscale mapping curves.

In embodiments, the mapping curve selection block 322 selects two grayscale mapping curves from among the grayscale mapping curves 511 to 514 based on the conversion ratio and performs fifth grayscale mapping based on the two grayscale mapping curves. A curve 515 can be calculated. For example, when the conversion ratio is 1.2, the mapping curve selection block 322 selects the conversion ratios closest to the first grayscale mapping curve 511 and the second grayscale mapping curve 512 (eg, the conversion ratio 1.2). grayscale mapping curves) are selected, and a fifth grayscale mapping curve 515 is obtained by interpolating (or extrapolating) the first grayscale mapping curve 511 and the second grayscale mapping curve 512. can be calculated

In embodiments, the grayscale mapping curves 511 to 514 may correspond to different on-pixel rate differences, respectively. For example, a target luminance of 400 nits and a reference on-pixel ratio (OPR) corresponding to a test image having a final luminance equal to the target luminance may be 10%. That is, when the on-pixel ratio (OPR) of the input image data is changed to 10%, the display device 100 can display the display image with a target luminance of 400 nits.

In this case, the second grayscale mapping curve 512 corresponds to the second on-pixel ratio difference of 15% (eg, on-pixel ratio of 25% - reference on-pixel ratio of 10%), and the third grayscale mapping curve 513 corresponds to the second on-pixel ratio difference of 40% (eg, on-pixel ratio of 50% - reference on-pixel ratio of 10%), and the fourth grayscale mapping curve 514 corresponds to the second on-pixel ratio of 65%. 4 On-pixel ratio difference (eg, on-pixel ratio of 75% - reference on-pixel ratio of 10%) may be corresponded to.

In this case, the mapping curve selection block 322 determines the on-pixel rate difference (eg, the difference between the on-pixel rate calculated in the analysis block 311 and the on-pixel rate corresponding to the target luminance calculated in the modeling block 312). ), one grayscale mapping curve may be selected from among the grayscale mapping curves 511 to 514.

In embodiments, the grayscale mapping curve may be set to increase the luminance of a specific grayscale (or the luminance of a specific object included in the displayed image) while lowering the on-pixel ratio of the input image data.

Referring to FIG. 5B , along the eleventh grayscale mapping curve, a grayscale value in a high grayscale region (eg, a range between the second grayscale value G2 and the maximum grayscale value) becomes high, and other regions (eg, a range between the second grayscale value G2 and the maximum grayscale value) For example, a grayscale value in a range between 0 and the first grayscale value G1 may be lowered.

That is, the display device 100 may not only increase the final luminance of the display image by lowering the on-pixel ratio of the input image data, but also increase the luminance of an object included in the input image data (or display image). brightness can be increased.

Referring to FIG. 5C , the object OB included in the display image IMAGE corresponds to nine pixels PX_C and PX_S, and the center pixel PX_C located in the center of the object OB has a maximum gray level of 255 pixels. , and the remaining pixels PX_S may correspond to 250 grayscale. In this case, the display device 100 may convert the remaining pixels PX_S to 254 grayscale, and the luminance of the central pixel PX_C may be supplemented using the increased luminance of the remaining pixels PX_S. That is, the display device 100 may control the final luminance to be equal to the target luminance by increasing the luminance (or average luminance) of the object OB.

Referring back to FIG. 3 , the mapping block 323 converts input image data (eg, first data DATA1) based on one grayscale mapping curve selected by the mapping curve selection block 322 to convert the input image data. Image data (or output image data) (eg, second data DATA2) may be generated. That is, the mapping block 323 may convert a grayscale value included in the input image data (eg, the first data DATA1) based on the grayscale mapping curve selected by the mapping curve selection block 322. there is. In this case, the on-pixel rate of the converted image data may be lower than that of the input image data. That is, the on-pixel ratio of the input image data may be reduced while passing through the mapping block 323 .

As described with reference to FIGS. 3 to 5C , the image processing unit 160 (or image processing device) according to embodiments of the present invention turns on input image data (eg, first data DATA1). Calculate the pixel rate, calculate the final luminance of the display image based on the luminance change rate of the display image according to the on-pixel rate change rate, and calculate the final luminance so that the final luminance is equal to the target luminance (eg, luminance according to the HDR image). value can be converted. Accordingly, the image processing unit 160 may display an HDR image on the LDR display device.

In particular, as described with reference to FIGS. 4A and 4B , the final luminance (or actual luminance) of the displayed image increases as the on-pixel ratio of the input image data decreases, and as described with reference to FIGS. 5B and 5C Likewise, it may increase as the luminance of the object (or the grayscale value included in the object) increases. That is, the actual luminance of the display image (or the actual luminance of the object included in the display image) is "LDISP = (LOB - OPR) * C (provided that LDISP is the actual luminance of the display image, and LOB is the luminance of the object (or, grayscale value included in the object), OPR is the on-pixel rate of the input image data, and C is a constant)".

Therefore, the display device 100 (or the image processing unit 160) changes the on-pixel ratio of the input image data and/or the luminance of the object (grayscale value corresponding to the object) to create a display image (or object). According to the specifications of the display device 100, display may be performed with a target luminance higher than the maximum luminance.

6A and 6B are diagrams illustrating examples of actual luminance for each gray level of the display device of FIG. 1 .

Referring to FIGS. 3, 5A, and 6A, an eleventh luminance curve 611 is a display image displayed by the display device 100 based on converted image data (eg, second data DATA2). Indicates actual luminance, and the twelfth luminance curve 612 may represent ideal luminance of a display image displayed by the display device 100 based on input image data (eg, first data DATA1). The twelfth luminance curve 612 may be substantially the same as the first luminance curve 211 described with reference to FIG. 2 .

For example, the display device 100 may convert input image data into converted image data using the second grayscale mapping curve 512 shown in FIG. 5A . In this case, the actual luminance of the displayed image corresponding to the grayscale value in the high grayscale region (for example, a grayscale value greater than a specific grayscale value) corresponds to the second grayscale mapping curve 512 and the twelfth luminance curve 612 ) may appear higher than the luminance of the phase. Also, actual luminance of the display image corresponding to a grayscale value (eg, a grayscale value smaller than a specific grayscale value) in the low grayscale region may appear lower than the luminance on the twelfth luminance curve 613 .

For reference, the display device 100 may supply a driving current to the display panel 110 (or the pixel PX) within a limited maximum driving current. Accordingly, the display device 100 redistributes the driving current based on the grayscale values of the pixels within the maximum driving current (ie, supplies less pixel driving current to pixels corresponding to the grayscale values in the low grayscale region; By supplying more pixel driving current to pixels corresponding to grayscale values in the high grayscale region), a luminance range wider than a preset luminance range (eg, 0 to 300 nits) (eg, 0 to 500 nits) You can display an image with .

Referring to FIGS. 3, 5B, 6A, and 6B , a twenty-first luminance curve 621 is displayed by the display device 100 based on converted image data (eg, second data DATA2). Actual luminance of the displayed image may be indicated.

For example, the display device 100 may convert input image data into converted image data using the 11th grayscale mapping curve 521 shown in FIG. 5B. In this case, the actual luminance of the display image corresponding to the grayscale value in the high grayscale region (for example, a grayscale value greater than a specific grayscale value) corresponds to the twelfth luminance curve 612 corresponding to the 11th grayscale mapping curve 521. It may be higher than the luminance of the phase. The twenty-first luminance curve 621 is similar to the eleventh luminance curve 611 shown in FIG. 6A , but the maximum luminance of the twenty-first luminance curve 621 may be lower than the maximum luminance of the eleventh luminance curve 611 . However, the luminance corresponding to a grayscale value (for example, a grayscale value greater than the fourth grayscale value G4) in a specific grayscale range on the twenty-first luminance curve 621 is greater than the luminance on the eleventh luminance curve 611. can That is, the display device 100 has a wider luminance range (eg, 0 to 500 nits) than a preset luminance range (eg, 0 to 300 nits) by increasing the luminance of an object included in the display image. video can be displayed.

7 is a flowchart illustrating an image processing method according to embodiments of the present invention, FIG. 8 is a flowchart illustrating an example of calculating a final luminance included in the method of FIG. 7 , and FIG. 9 is a flowchart of the method of FIG. 7 . It is a flowchart illustrating an example of a step of converting a grayscale value included in .

Referring to FIGS. 1, 3, and 7 to 9 , the method of FIG. 7 may be performed in the display device 100 (or image processing device).

The method of FIG. 7 may calculate an on-pixel ratio of input image data (eg, first data DATA1) (S710). Here, the on-pixel ratio (OPR) is the ratio of the number of activated pixels based on the input image data to the total number of pixels included in the display panel 110, as described above with reference to FIG. 1 . can represent

The method of FIG. 7 may calculate the final luminance of the display image based on the luminance change rate of the display image (or the luminance change rate of the display image according to the on-pixel rate change) (S720). Here, the final luminance is the predicted luminance value of the display panel 110, and the method of FIG. 7 may calculate the final luminance using a set value in which material characteristics of the display panel 110 are reflected.

Referring to FIG. 8 , the method of FIG. 8 calculates the luminance change rate of the display image according to the on-pixel rate change (S810), and calculates the final luminance of the display image based on the on-pixel rate and the luminance change rate of the display image. It can (S820).

For example, the method of FIG. 8 may calculate a luminance change rate of a display image according to a change in an on-pixel rate based on test data (or test images) having different on-pixel rates. For example, the method of FIG. 8 may calculate a luminance change rate of a display image according to a change in an on-pixel ratio using a preset calculation formula (eg, [Equation 1]). Meanwhile, the luminance change rate may increase as the on-pixel ratio decreases, as described with reference to FIGS. 4A and 4B .

For example, the method of FIG. 8 may calculate the final luminance of the display image based on the ideal luminance, on-pixel rate, and luminance change rate for the maximum grayscale value of the input image data.

Referring back to FIG. 7 , the method of FIG. 7 may convert grayscale values included in the input image data based on the final luminance and target luminance of the display image (S730).

Referring to FIG. 9 , the method of FIG. 9 calculates a conversion ratio based on the final luminance and target luminance (S910), selects a first grayscale mapping curve from among a plurality of grayscale mapping curves based on the conversion ratio (S920). ), the grayscale value may be converted based on the first grayscale mapping curve selected from among the plurality of grayscale mapping curves (S930).

For example, the method of FIG. 9 may determine whether the final luminance is greater than the target luminance, and calculate a conversion ratio when the final luminance is less than the target luminance. Here, the conversion ratio may indicate a ratio of target luminance to final luminance.

Meanwhile, the plurality of grayscale mapping curves may correspond to different conversion ratios, respectively, as described with reference to FIG. 5A .

In one embodiment, the method of FIG. 9 may convert input image data to reduce the on-pixel ratio of the display image based on the first grayscale mapping curve. Also, the method of FIG. 9 may convert input image data to increase average luminance of objects included in the display image based on the first grayscale mapping curve.

Since the configuration for converting input image data is substantially the same as the configuration for converting input image data previously described with reference to FIGS. 6A and 6B , overlapping descriptions will not be repeated.

As described with reference to FIGS. 7 to 9 , an image processing method according to embodiments of the present invention calculates an on-pixel rate of input image data (eg, first data DATA1), and calculates an on-pixel rate. The final luminance of the display image may be calculated based on the luminance change rate of the display image according to the change rate of , and the grayscale value may be converted so that the final luminance is equal to the target luminance (eg, luminance according to the HDR image). Accordingly, the image processing method may display an HDR image in an LDR display device.

Although the image processing apparatus and image processing method according to the embodiments of the present invention have been described with reference to the drawings, the above description is exemplary and is based on common knowledge in the related art to the extent that it does not deviate from the technical spirit of the present invention. It can be modified and changed by those who have it.

An image processing device and an image processing method according to embodiments of the present invention may be applied to various display systems. For example, the image processing device and image processing method may be applied to televisions, computer monitors, laptops, digital cameras, cellular phones, smart phones, PDAs, PMPs, MP3 players, navigation systems, video phones, and the like.

100: display device 110: display panel
120: scan driver 130: data driver
140: power supply unit 150: timing control unit
160: image processing unit 211: first luminance curve
212: second luminance curve 310: calculation unit
311 analysis block 312 modeling block
320: image conversion unit 321: luminance determining block
322: mapping curve selection block 323: mapping block
511 to 515: first to fifth grayscale mapping curves
521: 11th grayscale mapping curve
611: eleventh luminance curve 612: twelfth luminance curve
621: 21st luminance curve

Claims (20)

a calculation unit that calculates an on-pixel rate of input image data, and calculates a final luminance of the display image based on a luminance change rate of the display image according to a change in the on-pixel rate; and
an image converter configured to convert grayscale values included in the input image data based on a luminance change rate of the display image, the final luminance and the target luminance of the display image;
The video conversion unit,
a luminance determining block calculating a conversion ratio based on the final luminance and the target luminance;
a mapping curve selection block that selects a first grayscale mapping curve from among a plurality of grayscale mapping curves based on the conversion ratio; and
and a mapping block that converts the grayscale value based on the first grayscale mapping curve selected from among the plurality of grayscale mapping curves. The method of claim 1, wherein the calculator,
an analysis block calculating the on-pixel ratio of the input image data; and
and a modeling block that calculates the luminance change rate of the display image according to the on-pixel rate change, and calculates the final luminance of the display image based on the on-pixel rate and the luminance change rate of the display image. characterized image processing device. The image processing apparatus according to claim 2, wherein the modeling block calculates the luminance change rate of the display image according to the change of the on-pixel rate based on test data having different on-pixel rates. The image processing apparatus according to claim 2, wherein the luminance change rate increases as the on-pixel ratio decreases. The image processing apparatus of claim 2 , wherein the modeling block calculates the final luminance based on an ideal luminance for a maximum grayscale value of the input image data, the on-pixel rate, and the luminance change rate. delete The method of claim 1 , wherein the luminance determining block determines whether the final luminance is greater than the target luminance, and if the final luminance is less than the target luminance, determines a ratio of the target luminance based on the final luminance. An image processing device characterized in that for calculating the conversion ratio. The image processing apparatus according to claim 1, wherein the plurality of grayscale mapping curves respectively correspond to different conversion ratios. The image processing apparatus according to claim 1 , wherein the mapping block reduces the on-pixel ratio of the displayed image based on the first grayscale mapping curve. The image processing apparatus according to claim 1 , wherein the mapping block increases an average luminance of objects included in the display image based on the first grayscale mapping curve. in the display device,
calculating an on-pixel rate of input image data;
calculating a final luminance of the display image based on a luminance change rate of the display image according to a change in the on-pixel rate; and
converting a grayscale value included in the input image data based on the final luminance and the target luminance of the display image;
The step of converting the grayscale value included in the input image data,
calculating a conversion ratio based on the final luminance and the target luminance;
selecting a first grayscale mapping curve from among a plurality of grayscale mapping curves based on the conversion ratio; and
and converting the grayscale value based on the first grayscale mapping curve selected from among the plurality of grayscale mapping curves. 12. The method of claim 11, wherein the calculating of the final luminance of the display image comprises:
calculating the luminance change rate of the display image according to the on-pixel rate change; and
and calculating the final luminance of the display image based on the on-pixel rate and the luminance change rate of the display image. 13. The method of claim 12, wherein the calculating of the luminance change rate of the display image comprises:
and calculating the luminance change rate of the display image according to the change in the on-pixel rate based on test data having different on-pixel rates. 13. The image processing method of claim 12, wherein the luminance change rate increases as the on-pixel ratio decreases. 13. The method of claim 12, wherein the calculating of the final luminance of the display image comprises:
and calculating the final luminance based on the ideal luminance for the maximum grayscale value of the input image data, the on-pixel rate, and the luminance change rate. delete 12. The method of claim 11, wherein calculating the conversion ratio comprises:
determining whether the final luminance is greater than the target luminance; and
and calculating the conversion ratio representing a ratio of the target luminance to the final luminance when the final luminance is less than the target luminance. 12. The image processing method of claim 11, wherein the plurality of grayscale mapping curves correspond to different conversion ratios, respectively. 12. The method of claim 11, wherein the converting of the grayscale value comprises:
and reducing the on-pixel ratio of the display image based on the first grayscale mapping curve. 12. The method of claim 11, wherein the converting of the grayscale value comprises:
The image processing method further comprising increasing an average luminance of objects included in the display image based on the first grayscale mapping curve.

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