CN100550120C - image processing method in liquid crystal display - Google Patents

Abstract

The invention relates to an image processing method of a liquid crystal display, which comprises the following steps: obtaining backlight parameters according to the image data; adjusting the backlight source according to the backlight parameter; obtaining a gray scale reference value according to the adjusted backlight source, wherein the gray scale reference value is between a first gray scale boundary value and a second gray scale boundary value; when the gray scale value of the image data is between the gray scale reference value and the first gray scale boundary value, converting the gray scale value of the image data into a corresponding output gray scale value according to the backlight parameter; and when the gray scale value of the image data is between the gray scale reference value and the second gray scale boundary value, converting the gray scale value of the image data into a corresponding output gray scale value according to a linear relation. The invention can improve the contrast of the image picture, increase the color level displayed by the image picture and make the image picture more vivid.

Description

Image treatment method in the LCD

Technical field

The invention relates to a kind of image treatment method, and particularly relevant for a kind of image treatment method of LCD.

Background technology

In general display, about improving image contrast's technology, mainly be that the image data of input is handled, by analyzing the various characteristics of whole image data on image bar chart (histogram), decide the change amount of original input image data, and adjust required backlight illumination, make adjacent GTG value difference big, and then improve the contrast of image apart from change.

Yet, can reach the purpose that improves the image contrast although adjust the image data of input, be after the image data change with input in the existing practice, adjust required backlight illumination more in addition; In other words, the adjustment of the processing of image data and backlight illumination is uncorrelated mutually.Thus, backlight illumination just can't relatively be adjusted with image data, and uneven phenomenon appears in the contrast that a little part may be arranged in the whole image frame, or the user can feel to have the bright especially or dark especially situation of some part to take place when watching image frame.

Summary of the invention

The objective of the invention is the image treatment method in a kind of LCD is provided,, promote the display quality of image frame in order to improve the contrast of image frame.

The present invention discloses the image treatment method in a kind of LCD, and the method comprises the following step: obtain a backlighting parameters according to an image data; Adjust a backlight according to backlighting parameters; Obtain a GTG reference value according to adjusted backlight, wherein this GTG reference value is between one first GTG boundary value and one second GTG boundary value; When the GTG value of image data is between the GTG reference value and the first GTG boundary value, the GTG value of image data is converted to corresponding output GTG value according to backlighting parameters; And when the GTG value of image data is between the GTG reference value and the second GTG boundary value, the GTG value of image data is converted to corresponding output GTG value according to a linear relationship.

According to technology contents of the present invention, the image treatment method of application of aforementioned LCD can improve the contrast of image frame, increases the gradation that image frame shows, and makes image frame distinct more.In addition, back light source brightness can carry out relative with image data and moderately adjust and control, and makes that backlight in the use can be more efficient, can not produce meaningless power attenuation, reduces the use power of backlight indirectly.

Description of drawings

Fig. 1 is the synoptic diagram that illustrates according to image processing system in a kind of LCD of the embodiment of the invention;

Fig. 2 is the process flow diagram that illustrates according to image treatment method in a kind of LCD of the embodiment of the invention;

Fig. 3 illustrates the synoptic diagram of putting the image bar chart that forms according to the input image data in order;

Fig. 4 is a kind of synoptic diagram of importing transformational relation between GTG value and the output GTG value that illustrates according to the embodiment of the invention.

Drawing reference numeral

102: backlighting parameters produces circuit

104: the pulse width modulation signal generating circuit

106: the image gray scale change-over circuit

200～212: step

Embodiment

Fig. 1 is the block schematic diagram that illustrates according to image processing system in a kind of LCD of the embodiment of the invention.This image processing system comprises that backlighting parameters produces circuit 102, pulse width modulation (pulsewidth modulation, PWM) signal generating circuit 104 and image gray scale change-over circuit 106.Backlighting parameters produces circuit 102 can receive the input image data, and produce backlighting parameters (backlight index), and then backlighting parameters is sent to respectively in pulse width modulation signal generating circuit 104 and the image gray scale change-over circuit 106 according to the input image data that receives.Pulse width modulation signal generating circuit 104 produces corresponding pulse width modulation signal according to the backlighting parameters that receives, so as to the brightness of control backlight.106 of image gray scale change-over circuits are according to the backlighting parameters and the adjusted back light source brightness that receive, will import image data and be converted to the image output data, are sent in the display panel to show again.

Fig. 2 is the process flow diagram of the disclosed image treatment method of the present invention.At first, obtain a backlighting parameters (step 200) according to an input image data.Owing to backlighting parameters is along with different input image datas changes, therefore before the decision backlighting parameters, the input image data can be organized into the image bar chart (histogram) on N rank, and then decides backlighting parameters according to the image bar chart.

Fig. 3 illustrates the synoptic diagram of putting the image bar chart that forms according to the input image data in order.This image bar chart representative between minimum gray value 0 and maximum gray value N, is added up the number of times of each the GTG value appearance that gets according to statistical magnitude k in an image.In addition, this image bar chart also provides image characteristics, for example bright-dark degree.

After the number of times of obtaining each GTG value appearance, just can following mathematical expression (1) decide backlighting parameters.

$\mathrm{BI}=\mathrm{BIB}+\frac{H}{\mathrm{TP}}\×\frac{(M-\mathrm{GLB})}{2}---\left(1\right)$

Wherein, BI is a backlighting parameters; BIB is worth a pairing backlighting parameters boundary value for the maximum gray of time pixel in the input image data; H is the number of times of the maximum gray value appearance of time pixel in the input image data; The number of times that TP occurs for all GTG values in the input image data and; M is the maximum gray value of time pixel in the input image data; GLB is worth a pairing GTG boundary value for the maximum gray of time pixel in the input image data.

Because in some image, the image of high gray value (or low GTG value) may only account for few part, therefore more accurate in order to ensure the backlighting parameters that obtains, make image output can have relative brightness preferably or contrast, comprise backlighting parameters boundary value BIB and GTG boundary value GLB in the above-mentioned mathematical expression (1), in order to determine backlighting parameters more accurately, with the required backlight illumination of image of control high gray value (or low GTG value).

Table (one)

Grey-scale range	GTG boundary value (GLB)	Backlighting parameters boundary value (BIB)
			0～N/k	GLB 1	BIB 1
N/k～2*(N/k)	GLB 2	BIB 2
			...	...	...
(k-2)(N/k)～(k-1)(N/k)	GLB(k-1)	BIB(k-1)
			(k-1)(N/k)～N	GLB k	BIB k

Last tabulation (one) is the table of comparisons of expression backlighting parameters boundary value and the relative image gray scale scope of GTG boundary value.The maximum gray value of time pixel in the input image data, promptly Max (R, G, B), when falling within grey-scale range 0～N/k, with GLB 1 as the GTG boundary value of importing image; (when B) falling within grey-scale range N/k～2* (N/k), with the GTG boundary value of GLB 2 as the input image, the rest may be inferred for R, G as Max.On the other hand, when Max (R, G, when B) falling within grey-scale range 0～N/k, with BIB 1 as the input image the backlighting parameters boundary value; (when B) falling within grey-scale range N/k～2* (N/k), with the backlighting parameters boundary value of BIB 2 as the input image, the rest may be inferred for R, G as Max.

After obtaining backlighting parameters, adjust backlight according to obtained backlighting parameters again, wherein can produce a corresponding pulse width modulation (pulse width modulation, PWM) signal (step 202) according to backlighting parameters earlier.Then, relend by the pulse width modulation signal adjustment backlight (step 204) that produces.In addition, in order to control the brightness of backlight exactly, backlight illumination can be divided into the N rank, respectively by the darkest 0 rank of brightness to the brightest (N-1) rank of brightness, obtain look into value table (the lookup table of the backlighting parameters on N rank whereby to backlight illumination, LUT), and then set relation between backlighting parameters and the brightness, so as to the control backlight illumination according to the situation of reality and demand.

Moreover, after adjusting backlight, obtaining GTG reference value (step 206) according to the brightness of a backlighting parameters and adjusted backlight, this GTG reference value is between one first GTG boundary value and one second GTG boundary value.

Fig. 4 is a kind of synoptic diagram of importing transformational relation between GTG value and the output GTG value that illustrates according to the embodiment of the invention.In the present embodiment, the brightness of backlight strengthens according to backlighting parameters adjustment, and the first GTG boundary value is less than the second GTG boundary value, and the GTG reference value is between the intermediate value between first and second GTG boundary value and the second GTG boundary value, and promptly the GTG reference value is close to the second GTG boundary value.The first GTG boundary value is the minimum gray value in the image frame, and the second GTG boundary value is the maximum gray value in the image frame.As shown in the figure, X1 is the GTG reference value, 0 and N be respectively the first and second GTG boundary values, and GL _INBe input GTG value, GL _OUTBe output GTG value.X1 can be decided by following mathematical expression (2).

${\mathrm{<figure-callout\; id="1"\; label="X"\; filenames="C20071018879000131.png,C20071018879000141.png"\; state="\{\{state\}\}">X</figure-callout>}}_1=\frac{(F-1)\&times;N}{F\&times;\sqrt[r]{\frac{{\mathrm{BL}}_{\mathrm{Max}}}{{\mathrm{BL}}_{\mathrm{Dim}}}}-1}---\left(2\right)$

Wherein, BL _MaxBe the brightness of backlight complete opening, BL _DimFor according to the obtained corresponding backlight illumination of backlighting parameters, γ is a parameter gamma value, and N is the maximum gray value of input, and F is the maximum gray value of the output ratio with respect to the maximum gray value of input.

Then, after obtaining the GTG reference value, differentiate the GTG value GL of input image data _INWhether less than GTG reference value X1 (step 208).As input GTG value GL _INDuring less than GTG reference value X1, promptly when input GTG value between 0 and GTG reference value X1 between the time, will import GTG value GL according to backlighting parameters _INBe converted to corresponding output GTG value GL _OUT(step 210) wherein can will be imported the GTG value and be converted to corresponding output GTG value according to the brightness of gamma value of being obtained by backlighting parameters and adjusted backlight.Output GTG value GL _OUTCan decide by following mathematical expression (3).

${\mathrm{GL}}_{\mathrm{OUT}}=\sqrt[r]{\frac{{\mathrm{BL}}_{\mathrm{Max}}}{{\mathrm{BL}}_{\mathrm{Dim}}}}\&times;{\mathrm{GL}}_{\mathrm{IN}}---\left(3\right)$

On the other hand, as input GTG value GL _INDuring greater than GTG reference value X1, promptly as input GTG value GL _INIn the time of between GTG reference value X1 and N, will import GTG value GL according to a linear relationship _INBe converted to corresponding output GTG value GL _OUT(step 212).Output GTG value GL _OUTCan decide by following mathematical expression (4).

${\mathrm{GL}}_{\mathrm{OUT}}=\frac{{\mathrm{GL}}_{\mathrm{IN}}}{F}+\frac{(F-1)\&times;N}{F}---\left(4\right)$

Thus, the image of high gray value (or low GTG value) also can have contrast preferably after via conversion, allow the user can clearly differentiate the level of color.

In addition, in another embodiment, the brightness of backlight weakens according to backlighting parameters adjustment, and the first GTG boundary value is greater than the second GTG boundary value, and the GTG reference value is between the intermediate value between first and second GTG boundary value and the second GTG boundary value.The first GTG boundary value is the maximum gray value in the image frame, and the second GTG boundary value is the minimum gray value in the image frame; That is, X1 is the GTG reference value, and N and 0 is respectively the first and second GTG boundary values.At this moment, as input GTG value GL _INDuring less than GTG reference value X1, promptly when input GTG value between 0 with GTG reference value X1 between the time, foundation one linear relationship will be imported GTG value GL _INBe converted to corresponding output GTG value GL _OUTAs input GTG value GL _INDuring greater than GTG reference value X1, promptly as input GTG value GL _INIn the time of between GTG reference value X1 and N, will import GTG value GL according to backlighting parameters _INBe converted to corresponding output GTG value GL _OUT

By the embodiment of the invention described above as can be known, the image treatment method of application of aforementioned LCD can improve the contrast of image frame, increases the gradation that image frame shows, and makes image frame distinct more.In addition, back light source brightness can carry out relative with image data and moderately adjust and control, and makes that backlight in the use can be more efficient, can not produce meaningless power attenuation, reduces the use power of backlight indirectly.

Though the present invention discloses as above with embodiment; right its is not in order to limit the present invention; any have a technical field of the invention know the knowledgeable usually; without departing from the spirit and scope of the present invention; can be used for a variety of modifications and variations, so protection scope of the present invention is worked as with being as the criterion that the claim scope is defined.

Claims (11)

1. An image processing method for a liquid crystal display, said method comprising: (a) Obtaining a backlight parameter according to an image data, the calculation formula of the backlight parameter is: $\mathrm{BI}=\mathrm{BIB}+\frac{h}{\mathrm{TP}}\&times;\frac{(m-\mathrm{GLB})}{2},$ Among them, BI is the backlight parameter, BIB is a backlight parameter boundary value corresponding to the maximum grayscale value of the sub-pixel in the input image data, H is the number of occurrences of the maximum grayscale value of the sub-pixel in the input image data, and TP is the input image The sum of the occurrence times of all grayscale values in the data, M is the maximum grayscale value of the subpixel in the input image data, and GLB is a grayscale boundary value corresponding to the maximum grayscale value of the subpixel in the input image data; (b) adjusting a backlight source according to the backlight parameters; (c) Obtaining a grayscale reference value according to the backlight parameters and the adjusted backlight source, wherein the grayscale reference value is between a first grayscale boundary value and a second grayscale boundary value Between, the calculation formula of the gray scale reference value is: $x_1=\frac{(f-1)\&times;N}{f\&times;\sqrt[\mathrm{\&gamma;}]{\frac{{\mathrm{BL}}_{\mathrm{Max}}}{{\mathrm{BL}}_{\mathrm{Dim}}}}-1},$ Among them, X1 is the grayscale reference value, BL _Max is the brightness at which the backlight is fully turned on, BL _Dim is the corresponding backlight brightness obtained according to the backlight parameters, γ is a parameter gamma value, N is the maximum grayscale value input, F is the ratio of the maximum grayscale value of the output to the maximum grayscale value of the input; (d) When the grayscale value of the image data is between the grayscale reference value and the first grayscale boundary value, the grayscale value of the image data is adjusted according to the backlight parameter The scale value is converted into the corresponding output gray scale value, and its calculation formula is: ${\mathrm{GL}}_{\mathrm{out}}=\sqrt[\mathrm{\&gamma;}]{\frac{{\mathrm{BL}}_{\mathrm{Max}}}{{\mathrm{BL}}_{\mathrm{Dim}}}}\&times;{\mathrm{GL}}_{\mathrm{IN}},$ Wherein GL _IN is an input grayscale value, GL _OUT is an output grayscale value; and (e) when the grayscale value of the image data is between the grayscale reference value and the second grayscale boundary value Between, according to a linear relationship, the grayscale value of the image data is converted into a corresponding output grayscale value, the calculation formula is: ${\mathrm{<span\; class="notranslate">\; GL</span>}}_{\mathrm{<span\; class="notranslate">\; out</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; GL</span>}}_{\mathrm{<span\; class="notranslate">\; IN</span>}}}{\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; +</span>\frac{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; N</span>}}{\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; .</span>$ 2. The image processing method according to claim 1, wherein the brightness of the backlight source is adjusted and enhanced according to the backlight parameters, and the boundary value of the first gray scale is smaller than the second gray scale Boundary value. 3. The image processing method according to claim 2, wherein said grayscale reference value is an intermediate value between said first and second grayscale boundary values and said second grayscale boundary value between. 4. The image processing method according to claim 2, wherein said first grayscale boundary value is the minimum grayscale value in an image frame, and said second grayscale boundary value is in said image frame The maximum grayscale value of . 5. The image processing method according to claim 1, wherein the brightness of the backlight source is adjusted and weakened according to the backlight parameter, and the boundary value of the first gray scale is greater than the second gray scale Boundary value. 6. The image processing method according to claim 5, wherein said grayscale reference value is located between an intermediate value between said first and second grayscale boundary values and between said second grayscale boundary value between. 7. The image processing method according to claim 5, wherein said first grayscale boundary value is the maximum grayscale value in an image frame, and said second grayscale boundary value is in said image frame The minimum grayscale value of . 8. The image processing method as claimed in claim 1, wherein step (c) further comprises: obtaining a gamma value according to the backlight parameter; and The grayscale reference value is obtained according to the gamma value and the adjusted brightness of the backlight. 9. The image processing method according to claim 8, wherein the adjusted brightness of the backlight source is obtained through a look-up table. 10. The image processing method as claimed in claim 8, wherein step (d) further comprises: The grayscale value of the image data is converted into a corresponding output grayscale value according to the gamma value and the adjusted brightness of the backlight source. 11. The image processing method as claimed in claim 1, wherein step (b) further comprises: generating a corresponding pulse width modulation signal according to the backlight parameter; and The backlight source is adjusted by the pulse width modulation signal.

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