1. A tone mapping method for adjusting a contrast of an image, the method comprising: generating a luminance histogram of the image according to a luminance and a sharpness of the image, wherein the step of generating the luminance histogram of the image according to the luminance and the sharpness of the image comprises: dividing the image into a plurality of blocks; calculating an average luminance of pixels in each block of the plurality of blocks, respectively, to generate a block average luminance histogram corresponding to the plurality of blocks; calculating an average sharpness of pixels in each block of the plurality of blocks, respectively, to generate a block average sharpness histogram corresponding to the plurality of blocks; and summing the block average luminance histogram and the block average sharpness histogram to generate the luminance histogram corresponding to the image; performing a histogram equalization operation on the luminance histogram to generate a luminance mapping function corresponding to the image; performing a weighted operation on the luminance mapping function and a linear function to generate a weighted luminance mapping function corresponding to the image; generating a tone mapping look-up table corresponding to the image according to the weighted luminance mapping function; and adjusting the luminance of the image according to the tone mapping look-up table, so as to adjust the contrast of the image.