System and method for enhancement of coded images using adaptive spatial filtering
First Claim
1. A method for enhancing a low bit-rate encoded image, the method implemented on a computer having a memory and comprising the steps of:
- receiving a low bit-rate encoded image comprising pixels;
classifying said pixels into a first, a second, and a third pixel category, wherein the first, second, and third pixel categories are quasi-constant, textural, and dominant edge, respectively, and wherein the step of classifying comprises the substeps of;
setting the value of selected pixels in the received low bit-rate encoded image to zero to form a modified image;
determining an a-level zero-crossing measurement as a function of the pixels in the modified image and the pixels in the received low bit-rate encoded image; and
using the a-level zero-crossing measurement to classify said pixels into the quasi-constant and textural categories;
applying a first enhancement method to the pixel in the quasi-constant category; and
applying a second enhancement method to the pixels in the dominant-edge category;
whereby an enhanced image is generated.
7 Assignments
0 Petitions
Accused Products
Abstract
Pixels in a low bit-rate encoded image are categorized into two or more categories. In one embodiment three pixel categories are used: 1) pixels belonging to quasi-constant (QC) regions where the pixel intensity values vary slowly (e.g., pictorial portions), 2) pixels belonging to textured regions which are characterized by many small edges and thin-line signals (e.g., text portions), and 3) pixels belonging to dominant-edge (DE) regions which are characterized by few sharp and dominant edges (e.g., edge portions). In one embodiment DE pixels are categorized first, then QC and textural pixels are distinguished from the remaining pixels using the number of zero-crossings among the pixels and a threshold. Conventional spatial filters that are well suited for each pixel category type are then used to enhance each region of the image. In one embodiment, various combinations of spatial filters are used to enhance the image.
-
Citations
15 Claims
-
1. A method for enhancing a low bit-rate encoded image, the method implemented on a computer having a memory and comprising the steps of:
-
receiving a low bit-rate encoded image comprising pixels; classifying said pixels into a first, a second, and a third pixel category, wherein the first, second, and third pixel categories are quasi-constant, textural, and dominant edge, respectively, and wherein the step of classifying comprises the substeps of; setting the value of selected pixels in the received low bit-rate encoded image to zero to form a modified image; determining an a-level zero-crossing measurement as a function of the pixels in the modified image and the pixels in the received low bit-rate encoded image; and using the a-level zero-crossing measurement to classify said pixels into the quasi-constant and textural categories; applying a first enhancement method to the pixel in the quasi-constant category; and applying a second enhancement method to the pixels in the dominant-edge category; whereby an enhanced image is generated. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 15)
-
-
13. Computer memory programmed to enhance a low bit-rate encoded image, the program comprising the steps of:
-
receiving a low bit-rate encoded image comprising pixels; classifying said pixels into a first, a second, and a third pixel category, wherein the first, second and third pixel categories are quasi-constant, textural, and dominant edge, respectively, wherein the step of classifying comprises the substeps of; setting the value of selected pixels in the received low bit-rate encoded image to zero to form a modified image; determining an a-level zero-crossing measurement as a function of the pixels in the modified image of the pixels in the received low bit-rate encoded image; determining a threshold value; and classifying pixels in the quasi-constant category and pixels in the textural category as a function of the a-level zero-crossing measurement and the threshold; applying a first enhancement method to the pixel in the quasi-constant category; and applying a second enhancement method to the pixels in the dominant-edge category; whereby an enhanced image is generated.
-
-
14. A computer storage device having a program for enhancing a low bit-rate encoded image, the program comprising the steps of:
-
receiving a low bit-rate encoded image comprising pixels; classifying said pixels into a first, a second, and a third pixel category, wherein the first, second, and third pixel category, wherein the first, second and third pixel categories are quasi-constant, textural, and dominant edge, respectively, wherein the step of classifying comprises the substeps of; determining a zero-crossing measurement as a function of the pixels in the reveived low bit-rate encoded image; setting the value of selected pixels in the received low bit-rate encoded image to zero to form a modified image; determining an a-level zero-crossing measurement as a function of the pixels in the modified image of the pixels in the received low bit-rate encoded image; comparing the zero-crossing measurement and the a-level zero-crossing measurement; and classifying pixels in the quasi-constant category and pixels in the textural category as a function of the comparing substep; applying a first enhancement method to the pixels in the quasi-constant category; and applying a second enhancement method to the pixels in the dominant edge category; whereby an enhanced image is generated.
-
Specification