Method for sharpening a digital image

• US 20040047514A1
• Filed: 09/05/2002
• Published: 03/11/2004
• Est. Priority Date: 09/05/2002
• Status: Active Grant

• Current Assignee: Monument Peak Ventures, LLC (Dominion Harbor Enterprises, LLC)
• Original Assignee: Eastman Kodak Company
• Inventors: B. Gindele, Edward, Gallagher, Andrew C.
• Granted Patent: US 7,228,004 B2
• Time in Patent Office: Days
• US Class Current: 382/270
• CPC Class Codes: G06T 5/004 Unsharp masking
• CPC Class Codes: G06T 5/75 Unsharp masking
• CPC Class Codes: G06V 10/30 Noise filtering

Abstract

A method of sharpening a digital image having image pixels values includes the steps of: determining a D_min value, representing a value corresponding to a minimum possible exposure for a system that produced the digital image; for each pixel value in the digital image providing a gain factor that is dependent on the difference between the pixel value and the D_min value, such that pixel values nearer the D_min value have smaller gain factors; and using the gain factors to sharpen the digital image.

Claims

1. A method of sharpening a digital image having image pixels values, comprising the steps of:

a) determining a D_min value, representing a value corresponding to a minimum possible exposure for a system that produced the digital image;

b) for each pixel value in the digital image providing a gain factor that is dependent on the difference between the pixel value and the D_min value, such that pixel values nearer the D_min value have smaller gain factors; and

c) using the gain factors to sharpen the digital image.

2. The method of sharpening a digital image claimed in claim 1, further comprising the steps of:

a) applying an image processing path including one or more image transforms to the digital image resulting in a rendered digital image;

b) using the gain factors to sharpen the rendered digital image.

3. The method of sharpening a digital image claimed in claim 1, further comprising the steps of:

a) applying an image processing path including one or more image transforms to the original digital image resulting in a rendered digital image;

b) applying the image processing path to the gain factors to form rendered gain factors; and

c) using the rendered gain factors to sharpen the rendered digital image.

4. The method claimed in claim 1, wherein the gain factors are provided by a lookup table that models a monotonic function of pixel value.

5. The method claimed in claim 4, wherein the monotonic function is increasing from the D_min value to a predetermined pixel value and constant for pixel values that exceed the predetermined pixel value.

6. A computer program product for performing the method claimed in claim 1.

7. The computer program product claimed in claim 6, wherein the method further comprises the steps of:

a) applying an image processing path including one or more image transforms to the original digital image, resulting in a rendered digital image; and

b) using the gain factors to sharpen the rendered digital image.

8. The computer program product claimed in claim 6, wherein the method further comprises the steps of:

a) applying an image processing path including one or more image transforms to the original digital image, resulting in a rendered digital image;

b) applying the image processing path to the gain factors to form rendered gain factors; and

c) using the rendered gain factors to sharpen the rendered digital image.

9. The computer program product claimed in claim 6, wherein the gain factors are provided by a lookup table that models a monotonic function of pixel value

10. The computer program product claimed in claim 9, wherein the monotonic function is increasing from the D_min value to a predetermined pixel value and constant for pixel values that exceed the predetermined pixel value.