1. A method for reconstructing a color data of a specified pixel, comprising: measuring a vertical color data difference index Cv and a horizontal color data difference index Ch according to color data of a first group of pixels included in a pixel array, wherein the first group of pixels include a plurality of pixels vertically adjacent to the specified pixel, a plurality of pixels horizontally adjacent to the specified pixel, and at least one other pixel non-vertical and non-horizontal to the specified pixel; and executing one of a plurality of preset interpolation algorithms, which is selected according to a comparing result of the vertical color data difference index Cv and horizontal color data difference index Ch, thereby obtaining a reconstructed color data; wherein the specified pixel is one of the pixels included in a Bayer pattern, the specified pixel contains first-component color data while missing second-component color data and third-component color data, pixels vertically and horizontally next to the specified pixel contain the second-component color data, and pixels diagonally next to the specified pixel contain the third-component color data; the reconstructed color data is the second-component color data; wherein the pixel array includes 5×5 pixels numbered as P 1 ˜P 25 row after row, the specific pixel is pixel P 13 , and the horizontal color data difference index Ch is obtained according to a formula of: 
 Ch=e 1*| GRh−GRavg|+e 2*| GBh−GBavg|+e 3*| R 11− R 13|+ e 4*| R 15− R 13|+ e 5*| G 14− G 12|+ e 6*| G 7− G 8|+ e 7*| G 9− G 8| wherein e 1 , e 2 , e 3 , e 4 , e 5 , e 6 and e 7 are preset coefficients; GRh is a difference between an estimated value of the second-component color data and a detected value of the first-component color data of the specified pixel; GBh is a difference between an estimated value of the second-component color data and an estimated value of the third-component color data of the specified pixel; GRavg is a difference between an averaged value of the second-component color data and an averaged value of the first-component color data of the pixel array; GBavg is a difference between an averaged value of the second-component color data and an averaged value of the third-component color data of the pixel array; R 11 , R 13 and R 15 are detected values of the first-component color data of pixels P 11 , P 13 and P 15 ; G 8 , G 12 and G 14 are detected values of the second-component color data of pixels P 8 , P 12 and P 14 ; and G 7 and G 9 are estimated values of the second-component color data of pixels P 7 and P 9 .