Non-linear adaptive image filter for filtering noise such as blocking artifacts
AssigneeSTMicroelectronics S.r.l.
InventorsMassimo Mancuso, Antonio Maria Borneo
Life of this patent
Estimating the term…
Abstract
A filter reduces artifacts, such as grid noise and staircase noise, in block-coded digital images with image block boundaries. The type of filtering is determined after an estimation of the image global metrics and local metrics. For areas of the image near grid noise, the filter performs low pass filtering. For image fine details, such as edges and texture, no filtering is performed so that masking is avoided. The filter operates in intra-field mode and uses a fuzzy logic process, pixel deltas, and dual ramp generators to determine the horizontal and vertical length of a processing window surrounding an image block boundary.
Claims23
An image filter, comprising:
- a metrics extractor that extracts global metrics and estimates local metrics from an image, wherein the image includes two image blocks having a block boundary between them, wherein the block boundary causes noise;
- and
- a de-blocker system, coupled to the metrics extractor, having a ramp generator that eliminates the noise from the image.
A method for reducing noise in block-coded digital images, the method comprising:
- dividing an input image into a plurality of image blocks, wherein each image block in the plurality of image blocks has a plurality of pixels, and wherein the plurality of pixels include a target pixel and a plurality of neighboring pixels adjacent to the target pixel;
- processing the plurality of image blocks such that the input image is represented by an aggregate of the plurality of image blocks having at least one image block boundary;
- estimating global metrics of the plurality of image blocks using information associated with horizontal edges and vertical edges of the plurality of image blocks;
- estimating local metrics of each pixel in the plurality of pixels in the plurality of image blocks using information associated with horizontal edges and vertical edges of the neighboring pixels;
- and
- de-blocking the input image using the de-blocking system, wherein the de-blocking system uses the ramp generator such that any artifacts from the image block boundary are reduced.
An image filter, comprising:
- a length generator that generates a length of an image block, wherein the image block includes a plurality of pixels;
- and
- a length interpolator, coupled to the length generator, that generates a plurality of ramp values associated with the plurality of pixels, wherein when the plurality of ramp values are combined with the plurality of pixels, respectively, the length interpolator generates interpolated gray level values associated with each pixel selected from among the plurality of pixels in the image block.
Dependencies are inferred from the claim text.