An image adjustment method includes the steps of: a) configuring a weight-value generator to receive first image data and specified data and to generate an adaptive weight value according to the first image data and the specified data; and b) configuring an image blender to receive the first image data and second image data, and to generate adjusted image data by blending the first image data and the second image data with reference to the adaptive weight value. The adaptive weight value has a magnitude that corresponds to a difference between the first image data and the specified data.