Image contrast correction system and method thereof

An image contrast correct system and method thereof is provided. Exploiting Fuzzy theorem to analysis the image, which the LCD is going to display, identify the correction strength to several levels and real time correct the image contrast according to the Fuzzy rule and the Fuzzy decision theorem. On the other hand, all image analysis, correction decision, and the contrast correction will be completed during one frame period. Utilizing this FCC method (Fuzzy Contrast Correction) can avoid the over-correction or the under-correction situation, can improve or enhance the image contrast properly.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a method and system of image contrast correction, and more particularly relates to a method and system of liquid crystal display image contrast correction with Fuzzy theory.

2. Description of the Prior Art

Nowadays, Liquid Crystal Display (LCD) is a kind of monitor apparatus with lots of advantage, such as, light, low volume, low power consumption, low radiation, low glitter and can save more space. However, the LCD monitor has a major disadvantage on image display is low contrast. Low contrast cause the image quality of LCD can't contend against the vivid image quality displayed from the plasma display panel and the traditional CRT monitor. The root cause of low contrast is because the liquid crystal can not completely covers the backlight. As this result, light leakage phenomenon occurs when the LCD shows the black image. At the same time, when the white image doesn't have enough illumination neither due to low luminance, the contrast of LCD will become quite low. One of the prior arts to solve this problem is to analysis the input signal by cumulative distribution function (CDF). However, CDF needs about 1˜2 frame time to calculate the data, it can not display the corrected image in real time and needs lots of electric storage apparatus to calculate the function.

One of the other prior arts to solve this problem is modifying the driver voltage of source driver IC to force gray scale shows brighter or darker image. This method doesn't need extra production cost and won't occupy the hardware space. However, part of response speed of the digital to analog converter (DAC) of external hardware circuit may limit the resolution of the image and DAC has large power consumption also.

The contrast of LCD determines the image quality, said, how to make LCD has better color quality by correct the image within finite luminance is a big issue.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provides a method and a system of liquid crystal display image contrast correction with Fuzzy theory, exploiting the Fuzzy theory to analysis the image that LCD is going to display and determine the contrast correction strength by Fuzzy rules.

Another object of the present invention is to provides a method and a system of liquid crystal display image contrast correction with Fuzzy theory, exploiting the Fuzzy theory to determine whether the image needs contrast correction or not. If the contrast of the image needs to be corrected, then decides the correction strength. Thus, it can improve the situation that all images are using the same, uniform correction strength to correct the image contrast.

Another object of the present invention is to provides a method and a system of liquid crystal display image contrast correction with Fuzzy theory, exploiting the Fuzzy theory and analysis, identify the correction strength to several levels. It may avoid the image over-correction or under-correction situation occur, improves the image contrast properly, makes the LCD image color more vivid and increase the product competitively.

Another object of the present invention is to provide a method and a system of liquid crystal display image contrast correction with Fuzzy theory. According to the image luminance distribution histogram, separate the image into two portions, one is dark and one is bright. Then, exploiting the Fuzzy theory to decide the contrast correction function let the LCD monitor keeps the image average brightness level but has better image display quality.

Another object of the present invention is to provide a method and a system of liquid crystal display image contrast correction with Fuzzy theory, analysis the whole image, decide the correction strength and correct the image color in one frame time. This method can save calculate process time and can correct the image contrast in real time to compensate the LCD low contrast congenital deficiency.

Another object of the present invention is to provide a method and a system of liquid crystal display image contrast correction with Fuzzy theory, process the Fuzzy theory and Fuzzy decision during the frame blanking time, the corrected image can be displayed to the LCD when the next image comes in. As this result, it achieves the goal to real time correct the image.

Another object of the present invention is to provide a method and a system of liquid crystal display image contrast correction with Fuzzy theory, correct the image by exponential correction. The exponential correction can maintain the original image characteristics, contour, can avoid the distortion situation when corrects the dark or the bright image.

Another object of the present invention is to provide a method and a system of liquid crystal display image contrast correction with Fuzzy theory, create an contrast correction function that relevant to current image by real time Fuzzy theory and Fuzzy decision.

So as to accomplish the above object, there are provided a method and a system of liquid crystal display image contrast correction with Fuzzy theory, exploiting a Fuzzy unit to Fuzzification the image data, then decide the correction strength according to the Fuzzy rule, collocate the contrast correction function to achieve the goal of real time image correction.

DESCRIPTION OF THE PREFERRED EMBODIMENT

There is shown a method and a system of image contrast correction according to one preferred embodiment of the present invention.

Referring toFIG. 1, illustrating the Fuzzy Correction system hardware block in accordance with a preferred embodiment of the present invention. The Fuzzy correction system10includes an average luminance analysis unit103, used to analysis input image and save the image luminance distribution information and image into a histogram storage unit101and a image storage unit102respectively. While the image input, analysis, storage completed, a Fuzzy unit104start to analysis the image with Fuzzy theory and then decides the proper correction strength of the image. After the Fuzzy unit104decided the correction strength, the enhancement unit105will read the image from the image storage unit102and corrects the image contrast with a contrast correction function which decided by the Fuzzy unit104. And then display the corrected image on the LCD panel. Besides, the average luminance analysis unit103, histogram storage unit101, image storage unit102, Fuzzy unit104, and the enhancement unit105may be combined as a Fuzzy image contrast correction programmable IC. As this result, the image contrast correction system will not increase the size of the LCD.

Referring toFIG. 2is a flow chart in accordance with a preferred embodiment of the present invention. After the image input through from a input panel (step20), start to analysis the image data to dig out the average gray scale value of the whole image within the input image data, and create an image luminance distribution histogram of the input image (step202). Next, saves the image luminance distribution histogram and the input image respectively (step201). After the image input (step20), analysis (step202), save (step201) completed, starts to sample the image luminance distribution histogram and to grab peak value of the major gray scale distribution (step203). Then Fuzzification the peak value and the average gray scale to a Fuzzy set (step204), exploiting loop up Fuzzy rule to determine the image correction strength (step205). Wait until the image correction strength decided, to correct the image luminance, enhance the image contrast (step206) via a contrast correction function and output the corrected image to LCD panel (step22).

There is a contrast correction function base be saved in an electric storage apparatus (i.e., Read-Only Memory or Random-Access Memory). The enhancement unit will correct the image depends on one contrast correction function of the contrast correction function base. After the Fuzzy unit processes the Fuzzy theory and Fuzzy decision analysis completed, the Fuzzy unit will search a proper contrast correction function from the pre-saved contrast correction function base, which is saved in the electric storage apparatus, to correct any possible image. Please referring toFIG. 3, is a contrast correction function diagram in accordance with a preferred embodiment of the present invention. The contrast correction function that was pre-saved in the contrast correction function base uses input luminance as x-axis and uses corrected luminance as y-axis to draw as four contrast correction curves. There are: H contrast correction curve32, M contrast correction curve34, L contrast correction curve36, and N contrast correction curve38respectively. The correct strength from strong to weak in order is: H contrast correction curve32>M contrast correction curve34>L contrast correction curve36>N contrast correction curve38. In other words, if one image needs H contrast correction curve32to correct it, that means this image doesn't have enough contrast rate. For example, one image has most of luminance distributes on the dark status and the Fuzzy unit decides this image needs to be corrected by the H contrast correction curve32, that means, the dark portion of this image doesn't need to be corrected. Just the image luminance higher than the luminance average value30portion need to be corrected via the upper side of H contrast correction curve (the right side curve of the luminance average value30), to modify the image which does not bright enough to brighter and enlarge the contrast between dark portion and bright portion. Besides, the contrast correction function is an exponential function, exploiting the exponential correction can maintain the original image characteristics, contour, and can avoid the distortion situation when corrects the dark or the bright image.

Referring toFIG. 4, is a timing flow chart in accordance with a preferred embodiment of the present invention. The image input flow40is going to input the image of the first frame, the image of the second frame, the image of the third image . . . in order (timing401, timing403, timing405. . . etc.). In the same time, the pipeline process flow50and the image output flow60are processing simultaneous. For example, during the image of the first frame input period (timing401), the timing pipeline process flow50starts to analysis the image average luminance (timing502) and saving the image luminance distribution histogram (timing501). After the image of the first frame input (timing401) complete, the LCD panel will process a frame blanking action in order to display the image of the second frame (timing403). Next, when image input flow40processing the frame blanking action to clear the image of the first frame (timing402), the pipeline process flow50sampling the luminance peak value (timing503), fuzzification (timing504), Fuzzy decision (timing505) and enhance the contrast of the image (timing506) at the same time. Due to the frame blanking action of LCD needs spend around 3000 clocks to clear the previous image, however, the process time of the hardware system of the present invention just needs500clocks to deal with the plurality of image analysis (timing503,504>, decision (timing505), enhancement (timing506) action. Thus, while the image of the second frame sent in (timing403), the corrected image of the first frame will be outputted (timing507) at the same time. The image output flow60will display the corrected image of the first frame to the LCD panel (timing601). Understandable, when image input flow processing the frame blanking action of the second frame (timing404), the system is processing all the analysis and decision of the image of the second frame (timing503,504,505and506) before outputs the corrected image. Since the image of the third frame sent in (timing405), the pipeline process flow50outputs the corrected image of the second frame (timing507) and the image output flow60displays the corrected image of the second frame to the LCD panel (timing602) at the same time. Exploiting this multitask mode to display whole corrected images.

Please referring toFIG. 5AandFIG. 5B, they are the diagrams illustrating the image luminance distribution histogram and the Fuzzy decision analysis flow in accordance with a preferred embodiment of the present invention. In this embodiment, the image luminance distribution is be drafted as an image luminance distribution histogram70with image luminance and pixel amount as coordinates. Exploiting the Fuzzy theory and Fuzzy decision and depends on the major peak value and the major peak value location of the image luminance distribution histogram70to determine the contrast correction strength. Grab two major peak values (peak value704, peak value705) from the higher side of the image luminance distribution histogram70based on the average luminance703and other two major peak values (peak value701, peak value702) from the lower side of the image luminance distribution histogram70based on the average luminance703. Then Fuzzification these four peak values701,702,704, and705, and process the first Fuzzy decision71(the first Fuzzy decision710of peak value701, the first Fuzzy decision711of peak value702, the first Fuzzy decision712of peak value704, and the first Fuzzy decision713of peak value705) depends on the first Fuzzy decision table (please referring toFIG. 6, is a rule table of the first Fuzzification in accordance with a preferred embodiment of the present invention) to get a first Fuzzy correction value. Next, after the first Fuzzy decision71is completed, process the second Fuzzy decision72(Fuzzy decision of dark portion720and Fuzzy decision of bright portion721) to determine the dark portion contrast correction strength and the bright portion contrast correction strength respectively. Then take the contrast correction strength result of Fuzzy decision of dark portion720and the contrast correction strength result of Fuzzy decision of bright portion721to figure out an proper contrast correction function base on look up the second Fuzzy decision table (please referring toFIG. 7, is a rule table of second fuzzification in accordance with a preferred embodiment of the present invention). In other words, it is to separate the image to two portions: one is dark and the other is bright, and exploiting the Fuzzy theory to analysis and decide the contrast correction function to keep the image average luminance but has better display quality.

Referring toFIG. 8, is a flow chart in accordance with a different embodiment of the present invention. After the image input through from an input panel (step80), the image data is analyzed to dig out the average gray scale of the whole image within the input image data, and create an image luminance distribution histogram of the input image (step802). Next, the image luminance distribution histogram and the input image are saved, respectively (step801). After the image input (step80), analysis (step802), save (step801) completed, start to sample the image luminance distribution histogram and to grab peak value of the major gray scale distribution (step803). Then the peak value and the average gray scale are processed with a Fuzzy method to a Fuzzy set (step804), exploiting Fuzzy number (Triangular Fuzzy Number, Non-Symmetric Fuzzy Number, Trapezoidal Fuzzy Number, Bell Shape Fuzzy Number . . . etc) and collocating with Fuzzy theory to decide a contrast correction function (step805). Wait until the image correction strength decided, correct the image luminance, enhance the image contrast (step806) by the contrast correction function and output the corrected image to LCD panel (step82).