A method for image processing by adjusting heating time includes providing a first heating table corresponding to a relationship between a first color density and a first heating time and a second heating table corresponding to a relationship between a color degree and a second heating time based on a printing parameter. The method further comprises providing a function corresponding to a relationship between a second color density and the color degree based on the first heating table and the second heating table, wherein the second heating time has a one-to-one relationship with the color degree, and the color degree has a one-to-one relationship with the second color density.