An objective metric for grayscale image quality capable of both global and localized quality assessment and based on a direct comparison of visual information in the test and reference images is proposed. The measure associates visual information with edge, or gradient, information that is initially extracted at all locations of the test and reference images. A perceptual-information preservation model is then used to quantify the success of information transfer/loss. By considering the perceptual importance of different image regions, local image quality success estimates are integrated into a single, numerical quality score between 0 (total information loss) and 1 (ideal transfer). The proposed metric is validated using extensive subjective test results. Results indicate that even in its basic form the proposed metric is perceptually meaningful and yields performance comparable with state-of-the art objective image quality metrics.