1. A fingerprint ridge image synthesis system, comprising: a memory storing instructions; one or more processors configured to execute the instructions to: set different wavelet wavelength (λ) and wavelet angle (θ) as parameter values of wavelets and set combinations of the wavelet wavelength and wavelet angle as parameter sets by corresponding to gradient of each pixel of the fingerprint image; perform continuous wavelet transform processing on partial regions within the fingerprint image corresponding to each of the pixels based on each of the different parameter sets, calculate consistency between the wavelets corresponding to each of the parameter sets and ridge shapes in each of the partial regions, and determine the parameter set of the highest consistency as the parameter set corresponding to each of the pixels; update the parameter values of the parameter sets of each of the pixels and each of neighboring pixels neighboring to those pixels to optimal values with which mutual continuity of the parameter values becomes optimum; and synthesize the ridge image by setting gray-scale values of each corresponding pixel based on the parameter sets constituted with the optimal values.