Apparatus and method for determining the appropriate amount of sharpening for an image

Claim 2

An image enhancing apparatus, comprising: (A) a filter that enhances the sharpness of an original image in accordance with a sharpening parameter; (B) a sharpening parameter selection system coupled to the filter, the sharpening parameter selection system determining the sharpening parameter for the filter such that the frequency distribution of a sharpened image of the original image by the filter is similar to that of a low resolution image of the original image.

Claim 3

The image enhancing apparatus of claim 1, wherein the sharpening parameter selection system further comprises (a) a low resolution image generator that generates the low resolution image of the original image; (b) a first Fourier transform generator coupled to the low resolution image generator to determine the frequency distribution of the low resolution image; (c) a parameterized Fourier transform generator that (1) generates a plurality of sharpened images of the original image based on a plurality of predetermined sharpening parameters and (2) determines the frequency distribution of each of the sharpened images; (d) a parameter selector coupled to the first Fourier transform generator and the parameterized Fourier transform generator to determine which one of the sharpened images has its frequency distribution similar to that of the low resolution image in order to select the sharpening parameter from the predetermined sharpening parameters.

Claim 4

The image enhancing apparatus of claim 2, wherein the parameterized Fourier transform generator further comprises (I) a sharpening filter that generates the plurality of sharpened images in accordance with the predetermined sharpening parameters; (II) a second Fourier transform generator that determines the frequency distribution of each of the sharpened images.

Claim 5

The image enhancing apparatus of claim 2, wherein the parameter selector determines which one of the sharpened images has its frequency distribution similar to that of the low resolution image by comparing the variance of the frequency distribution of the low resolution image with that of the sharpened images.

Claim 6

The image enhancing apparatus of claim 3, wherein each of the first and second Fourier transform generators is a discrete Fourier transform generator.

Claim 7

The image enhancing apparatus of claim 1, wherein each of the filter and the sharpening filter is an unsharp masking filter.

Claim 10

The method of claim 7, where the step (A) further comprises the steps of (I) generating a low resolution image of the original image; (II) performing a Fourier transformation operation to the low resolution image to determine the frequency distribution of the low resolution image; (III) generating a plurality of sharpened images of the original image based on a plurality of predetermined sharpening parameters; (IV) performing the Fourier transformation operation to each of the sharpened images to determine the frequency distribution of each of the sharpened images; (V) determining which one of the sharpened images has its frequency distribution similar to that of the low resolution image in order to select the sharpening parameter from the predetermined sharpening parameters.

Claim 11

The method of claim 8, wherein the step (V) further comprises the step of comparing the variance of the frequency distribution of the low resolution image with that of the sharpened images to determine which one of the sharpened images has its frequency distribution similar to that of the low resolution image.

Claim 12

The method of claim 8, wherein the step (V) further comprises the steps of (a) determining the variance of the frequency distribution of which one of the sharpened images has the smallest difference from that of the low resolution image; (b) selecting one of the predetermined sharpening parameter associated with that one of the sharpened images to be the selected sharpening parameter.

Claim 13

The method of claim 8, wherein the Fourier transformation operation is a discrete Fourier transformation operation.

Claim 16

The apparatus of claim 12, where the first set of instructions further comprises (a) a first subset of instructions that generate a low resolution image of the original image; (b) a second subset of instructions that perform a Fourier transformation operation to the low resolution image to determine the frequency distribution of the low resolution image; (c) a third subset of instructions that generate a plurality of sharpened images of the original image based on a plurality of predetermined sharpening parameters; (d) a fourth subset of instructions that perform the Fourier transformation operation to each of the sharpened images to determine the frequency distribution of each of the sharpened images; (e) a fifth subset of instructions that determine which one of the sharpened images has its frequency distribution similar to that of the low resolution image to select the sharpening parameter from the predetermined sharpening parameters.

Claim 17

The apparatus of claim 13, wherein the fifth subset of instructions determine which one of the sharpened images has its frequency distribution similar to that of the low resolution image by comparing the variance of the frequency distribution of the low resolution image with that of the frequency distribution of each of the sharpened images.

Claim 18

The apparatus of claim 13, wherein the fifth subset of instructions determine which one of the sharpened images has its frequency distribution similar to that of the low resolution image by (1) determining the variance of the frequency distribution of which one of the sharpened images has the smallest difference from that of the low resolution image, and (2) selecting one of the predetermined sharpening parameter associated with that one of the sharpened images to be the selected sharpening parameter.

Claim 19

The apparatus of claim 13, wherein the Fourier transformation operation is a discrete Fourier transformation operation.