Accession Number:

AD0773569

Title:

On Lightness,

Descriptive Note:

Corporate Author:

MASSACHUSETTS INST OF TECH CAMBRIDGE ARTIFICIAL INTELLIGENCE LAB

Personal Author(s):

• Horn,Berthold K. P.

Report Date:

1973-10-01

Pagination or Media Count:

53.0

Abstract:

The intensity at a point in an image is the product of the reflectance at the corresponding object point and the intensity of illumination at that point. One is able to perceive lightness, a quantity closely correlated with reflectance. How then does one eliminate the component due to illumination from the image on our retina. The two components of image intensity differ in their spatial distribution. A method is presented here which takes advantage of this to compute lightness from image intensity in a layered, parallel fashion. The method is developed for a restricted class of images first used by land in presenting his retinex theory of color. In this theory the problem of color perception is reduced to one of judging black and white lightness on three images taken in different parts of the visual spectrum. The method described here fills the need for a lightness judging process. Modified author abstract

Descriptors:

• *Pattern recognition
• *Visual perception
• *Color vision
• Images
• Signal processing
• Fourier transformation
• Computations

Subject Categories:

• Bionics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE