Algorithm & Front End Implementation For Graphics Engine In Large-Size LCD

In application of LCD, the image resolution of data source is variational. In order to meet the need of industry product standardization and get best display effect, the physical resolution of LCD is fixed. So the input image which resolution is variable should be zoomed and inputed into LCD. At present, a LCD graphics engine is used to realize the zooming process between the input data source and display. LCD graphics engine is a high integrated IC used for image processing. It is very important in LCD display system.In this paper, the research state of LCD graphics engine is firstly discussed. Then the structure and design target of LCD graphics engine is presented. A new interpolation algorithm named two-point cubic spline interpolation is proposed. Its interpolation kernel function alse be dirived. The image scaling engine is realized based on the interpolation algorithm. It is the key part of the LCD graphics engine. The experiments based on subjective evaluation and objective Q-evaluation show that the image quality comes from two-point cubic spline interpolation is very close to bicubic. But the operation complexity and handware spending is lower. It have a better performance-to-price ratio for the LCD graphics engine which demand a high real-time.In order to improve the image quality of the image scaling engine, the image color adjustment techniques are added into the LCD graphics engine. A Laplacian eight neighborhood template is used to sharpen the image edge. A betterment is maken to the Laplacian sharpen algorithm by adding the sharpen factor w. the user can controle the sharpen intensity according to own visual characteristic. After discussing the principle of existing contrast adjustment methods and analyzing the shortages of them, a subsection linearity transform contrast adjustment algorithm based on automatic double-threshold split is proposed. The method applys the ultimate category variance given by Otsu realize the automatic double-threshold split. It obtains the best split points and divides the image into target area, background area and transition area. Then the best split points are used to set the parameter of the subsection linearity transform contrast adjustment algorithm. At the same time, the user can control the contrast adjust intensity by the weight factor w, which can change the slope of the subsection line. The image simulation shows that the contrast adjust method is valid. After introducing the principle of Gamma correction, a pre-revise dividual-channel Gamma correction algorithm is presented according the respective RGB Gamma curve of LCD. It can reappear the original image better than the classical Gamma equal 2.2 through the simulation results.With the enlargement of LCD demand, the number of bits expressing a pixel is also added. But in many occasion of LCD application, due to the limit of the precision of the display terminal, the digital image expressed by multi-bit should be reduce the number of bits in order to match the display terminal. The digital halftoning technique is applied to solve this match problem. The ordered dither and error diffusion are two valid halftoning methods. Aiming at the inherent shortage of Bayer dither owing to the changeless dither matrix, a dynamic Bayer dither method whose dither matrix is alternated between the image frames is presented. It not only guarantees the gray informatio of image not change, but also degrades the inherent shortage of the Bayer dither matrix. In order to meet the development of slap-up LCD graphics engine, the error diffusion is alse discussed in this paper. A dynamic error diffusion method based on edge detect and avianize dither matrix is proposed. In this method, the edge direction of image is considered. The error diffusion coefficient is dynamic adjusted according the edge direction. In order to decrease the errer cumulation, a avianize dither matrix is presented. It can degrade the shortage of tortoise-texture in error diffusion. The dynamic error diffusion method based on edge detect and avianize dither matrix can get a better image quality from the subjective and objective evaluation.Based on those proposed algorithms and LCD structure, the handware description language Velilog HDL are used to realize the RTL description of LCD graphics engine IC. In order to depress the risk of ASIC design, the FPGA verification is imported into the design flow. After determining the scheme of FPGA verification for LCD graphics engine, the verification flatform is builded. Then the object code is downloaded into FPGA on the verification flatform. The result of FPGA verification shows that the front-end design of the LCD graphics engine IC is right. The image quality is good and it obtains an anticipative design target.