1. A pixel mixture method for mixing several pixels having different colors on a solid-state image sensing device, which is performed by an imaging device having said solid-state image sensing device with a color filter array (CFA) and multiple pixels, said method characterized in that a pixel mixture operation is performed based on a pixel mixture operation equation for said several pixels that are adjacent spatially using the imaging device, said pixel mixture is a weighting addition, i.e. an addition of results obtained by multiplying pixel value of each pixel of said several pixels by suitable pixel mixture weight corresponding to said each pixel of said several pixels, and said suitable pixel mixture weight is determined based on a predetermined parameter that is computed based on eigenvalues of A T A, where A represents a color conversion matrix computed based on pixel mixture weights, A T represents a transposed matrix of said color conversion matrix A, and the kind L of colors after said pixel mixture operation is an integer that is 3 or more than 3.