A kind of method of improving false contour of plasma image
Technical field
The present invention relates to a kind of image processing method that improves plasma scope picture quality, particularly a kind of method of improving false contour of plasma image.
Background technology
AC-PDP comprises a plurality of addressing electrodes and a plurality of perpendicular to keeping and scan electrode that addressing electrode is arranged.Addressing, keep that scan electrode all is coated with insulation course so that it separates with discharge space, at addressing electrode and keep, the place that intersects of scan electrode, form the discharge cell corresponding with pixel.
According to the vision physiological of human eye, when the repetition frequency of light pulse is higher than critical flicker frequency, can show different brightness by control light pulse number.AC-PDP adopts a son method, and a field duration is divided into N son field, and in each height field, light period is corresponding with the weighted value on acting on N position pixel data corresponding positions; Each son field comprises a reseting stage, and pixel data write phase and one keep glow phase; In the synchronous reset stage, all discharge cells are energized simultaneously and put to form the wall electric charge uniformly in each discharge cell among the PDP, in ensuing pixel data write phase, encourage the selection discharge operation according to the pixel data in each discharge cell; Keeping glow phase, luminescence unit all remains on the Discharge illuminating state in the weighted value of each height field in the corresponding time.
In order to realize that 256 grades of gray scales show, in 8 son fields, demonstration phase of each son field is cut apart on time shaft by binary weight, the interference when so just appearance shows dynamic image easily.Because people when watching moving object, have a kind of physiological instinct, promptly observer's viewpoint can move the action of being accustomed to when watching television image as people of watching object attentively by the accompany movement object together.The driving method that Color AC-PDP has adopted molecular field to show realizes that many gray scales show, the method of this realization gray scale requires can be luminous in the cycle of whole TV Field, luminous inhomogeneous on the time distributes will appear when showing moving object, because the visual persistence effect of human eye, thereby when human eye viewpoint accompany movement movement of objects, interference such as diplopia appear on retina, but as long as motion one stops, or observer's sight do not move with moving object, and the diplopia phenomenon will disappear.
In addition, the luminosity of CRT is to adjust by the intensity of the electron beam of simulation control impact fluorescence powder, and the gray shade scale of PDP is then kept umber of pulse adjustment by adjustment.For example, in order to show 256 grade gray scales, a TV Field is divided into 8 son fields, and output brightness degree of each son field is 2
n(0≤n<8), brightness degree the adding up of human eye impression for each sub-field brightness.The output brightness of PDP is linear change according to the input digit value, and CRT has the characteristic of non-linear output, in order to remedy the non-linear output characteristics of CRT, the television video frequency signal of input all passes through the gamma conversion, therefore, in order in PDP, to show real television image, need do corresponding adjustment, promptly anti-Gamma correction for the digital value of input.
In the anti-gamma conversion, the gray shade scale of input is through equation 1 conversion
In the formula, x represents that the gray shade scale imported, Y represent the gamma value of being scheduled to, and k represents the gray shade scale number of the maximum of white point representative, and Y is the desirable output display brightness number of degrees for input gray level grade X.
Picture signal is through behind the anti-Gamma correction, for low gray scale part, several gray shade scales can be merged into a gray-scale value output, and human eye is responsive for the variation of low gray scale part, this merging causes sudden change visually, the false contouring when also just having caused low gray shade scale.
Summary of the invention
In order to overcome the deficiency of above-mentioned technology, the present invention proposes a kind of method of improving false contour of plasma image, can suppress the generation of false contouring, improve the image displaying quality of PDP.
Technical scheme of the present invention is achieved in that
At first, current pixel receives the propagated error of other pixel, the current pixel gray-scale value adds that the propagated error of other pixels obtains new gray-scale value, with new gray-scale value integral part as an intermediate grey values, with the fraction part of new gray-scale value as intermediate error values;
Then, obtain showing the gray scale of usefulness by the gray-scale value of centre by look-up table, intermediate grey values and show the difference error by way of compensation of the gray scale of usefulness obtains compensating error and intermediate error values summation the error of this pixel;
At last, the error with this picture element spreads toward neighborhood pixels by the Floyd Steinberg error diffusion method of classics again.
The present invention obtains the error of current pixel point by said method, and the low gray scale false contouring and the motion false contouring of image have all obtained obvious suppression.
Description of drawings
Fig. 1 is 42 inches plasma data processing block diagrams.
Fig. 2 is an error diffusion part block diagram.
Embodiment
With reference to shown in Figure 1, for 42 inches PDP among the embodiment, its data handling procedure is: at first receive data-signal from interface, pass through then after the anti-gamma conversion, FloydSteinberg error diffusion method by classics carries out the error diffusion processing again, the following stated error diffusion method is the Floyd Steinberg error diffusion method of footpath allusion quotation: a sub-field transformation number, a son number is chosen as 12, driving according to the ADS driving method requires data are separated by the son field then, and the data storage of after separating is sent to the addressing driving circuit in frame memory storage.
During this is implemented, from the coding of 256 grades of gray scales, stimulate integration not produce the principle of false contouring earlier, pick out coding, represent 0-255 level gray scale with this group coding according to human eye.The gamma error that to introduce thus is diffused on the neighborhood pixels by error diffusion then.In the realization, adopt the mode of tabling look-up, will substitute gray scale and compensating error and deposit in the table, actual gray-scale value obtains gray-scale value and the compensating error that actual displayed is used by tabling look-up.This method has obvious suppression to low gray scale partial contour and motion false contouring.
With reference to shown in Figure 2, the original gray scale of pixel is through after the gamma conversion being, the error that receives the neighbor diffusion obtains Wij, then the integral part of Wij is overflowed judgement, if integral part more than or equal to 255, then the address of look-up table is 255, error amount is Eij=Wij-255, if integral part is less than 0, then the address of look-up table is 0, Eij=Wij.Otherwise the look-up table address is the integral part Iij of Wij, the compensating error ECij that look-up table is adopted during corresponding to this gray level when being used for gray-scale displayed value Gij and adopting new gray-scale value.The gray-scale value Gij of look-up table output is sent to back level processing and is used for showing, compensating error ECij and Eij sum spread toward neighbor as the new error of pixel.
View data is used as the numerical value of this fraction part as error through after the anti-gamma conversion, is diffused on the contiguous pixel.Like this, the brightness that human eye perceives arrives is loss not, and the integer that has remedied after the conversion of direct negate gamma is sent to the gray shade scale that is lost when the back level shows, the gray-level of the low gray scale part of human eye sensitivity can be embodied draw.
Because the existence of moving image dynamic false contours has a strong impact on picture quality.The method of son field is cut apart in employing, under the situation that does not influence brightness requirement, Jiang Yichang is divided into more a plurality of sons field as much as possible, makes that a son weight transition is even, can effectively avoid authority baryon field to have the luminous serious unevenness of being brought like this, can produce by inhibition false contouring to a certain degree.When cutting apart authority baryon field, adjust sub-field sequence, pick out suitable coding, reduce the non-uniform light of image in the gray scale progressive formation as far as possible.
The place of grayscale transition has the transition of big weight, and the present invention compensates the place of this grayscale transition, and the gray scale with compensation is diffused on the contiguous pixel according to a certain percentage then, like this, neither influence image and show, prior, can effectively suppress the generation of false contouring.
Through the method, low gray scale false contouring and motion false contouring have all obtained obvious suppression.
The present invention is exactly the restriction that has utilized the human eye retina to go up the resolution of photoreceptor, the resolution of human eye generally can be limited on roughly the radian, and the visual sense feeling of human eye is based on average brightness value around the pixel but not the brightness value of an independent pixel.If watch 42 inches plasm TV in 3 meters places far away of distance, the identification for image will be corresponding one 2 * 2 pixel scale so.Error-diffusion method just is based on this characteristic, and the output error of certain pixel is diffused on the pixel of closing on.
At first, view data through the value after the anti-gamma conversion, is used as the numerical value of fraction part as error, is diffused on the contiguous pixel.Like this, the brightness that human eye perceives arrives is loss not, and the integer that has remedied after the conversion of direct negate gamma is sent to the gray shade scale that is lost when the back level shows, the gray-level of the low gray scale part of human eye sensitivity can be embodied draw.
Because the existence of moving image dynamic false contours has a strong impact on picture quality.The method of son field is cut apart in employing, under the situation that does not influence brightness requirement, Jiang Yichang is divided into more a plurality of sons field as much as possible, makes that a son weight transition is even, can effectively avoid authority baryon field to have the luminous serious unevenness of being brought like this, can suppress false contouring and produce.When cutting apart authority baryon field, adjust sub-field sequence, the coding of picking out reduces the non-uniform light of image in the gray scale progressive formation with this.
Yet, have the transition of big weight in the place of some grayscale transition, only adopt and cut apart son and optimize the generation that Methods for Coding still can't effectively suppress false contouring.At this problem, the present invention compensates the place of this grayscale transition, and the gray scale with compensation is diffused on the contiguous pixel then, like this, neither influences image and shows the generation that can effectively suppress false contouring again.