Granted Patent B2

US 7,492,939 · App. 11/781,975 · Granted Feb 17, 2009

Abstract

Claims (15)

1. A method of enhancing a digital image comprising:

using a processor or computer to perform the steps of:

decomposing the provided digital image into a multi-frequency band representation of four frequency bands as follows:

(a) a lowest frequency band image which represents large-sized features in the digital image;

(b) a low-to-mid frequency band image which represents mid-sized features in the digital image;

(c) a mid-to-high frequency band image which represents the small-sized features in the digital image; and

(d) a highest frequency band which represents very fine detail in the digital image;

multiplying each of the high frequency band images with a gain factor;

summing together the unmodified low frequency band image and the modified high frequency band images to produce a reconstructed digital image; and

mapping the reconstructed digital image through a tone-scale look-up-table to map the reconstructed digital image to optical densities, the tone scale having a slope at a reference density that defines dynamic range control and wherein increasing the dynamic range reduces latitude of the digital image, while increasing the dynamic range decreases the latitude to the digital image, and manipulation of the dynamic range control does not affect the detail contrast or sharpness of small of fine detail of the image; and

including manipulating said low-to-mid frequency band image to produce a contrast effect without affecting the overall dynamic range of said digital image.

2. The method of claim 1 including manipulating the mid-to-high frequency band image to produce a sharpness or blurring effect of the small-sized features of the digital image.

3. The method of claim 1 including manipulating the highest frequency band image to produce a sharpness or blurring effect of very fine detail in the digital image.

4. The method of claim 1 wherein the mapping includes a brightness control for shifting the mean density of the digital image.

5. The method of claim 1 wherein the mapping further includes mapping the tone scale function to a standard gray scale display function for monochrome image presentation.

Assignments (8)