1. A tympanic membrane image analysis method, comprising: receiving a tympanic membrane image obtained from an otoscope, and classifying the tympanic membrane image into a plurality of anatomic regions based on a plurality of tissue types; coding each of the anatomic regions with a numerical number to describe its morbid condition; obtaining an eigenvalue through collecting the numerical numbers from each anatomic region; obtaining a matrix with a plurality of reference eigenvalues from an otitis media database, then calculating a plurality of contrast values by performing multiplication of the matrix and the eigenvalue with a weighting matrix for the numerical numbers of each anatomic region; and determining a type of ear infection from the tympanic membrane image in accordance with the lowest contrast value, the lowest contrast value being a reference eigenvalue; wherein the otitis media database is constructed through steps comprising: receiving a plurality of reference tympanic membrane images, wherein the reference tympanic membrane images are ear infections in different types; choosing one of the reference tympanic membrane images, and classifying into the anatomic regions based on the tissue types; coding each of the anatomic regions with the numerical number to describe its morbid condition; obtaining the reference eigenvalue through collecting the numerical number of each anatomic region; choosing other one of the reference tympanic membrane images repeatedly until obtaining the reference eigenvalues from each tympanic membrane image; and determining the otitis media database of ear infection in accordance with the matrix through sequentially arranging the reference eigenvalues of each reference tympanic membrane image.