137 results about "Ringing artifacts" patented technology

A technique to reduce blocking and ringing artifacts in low bit-rate block-based video coding is applied to each reconstructed frame output from the decoder. For each pixel block of a reconstructed frame, its DC value and DC values of the surrounding eight neighbor blocks are exploited to predict AC coefficients which might be lost in the quantization stage in the encoding process. The predicted AC coefficients are used to classify each reconstructed block as either a low-activity or a high-activity block. Low-pass filtering is then adaptively applied according to the classification of the block. Strong low-pass filtering is applied in low-activity blocks where the blocking artifacts are most noticeable, whereas weak low-pass filtering is applied in high-activity blocks where ringing noise as well as blocking artifacts may exist. The adaptive filtering reduces ringing noise as well as blocking artifacts without introducing undesired blur. In low activity blocks, the blocking artifacts are reduced by one dimensional horizontal and vertical low-pass filters which are selectively applied in either the horizontal and / or vertical direction depending on the locations and absolute values of the predicted AC coefficients. In high activity blocks, de-blocking and de-ringing is conducted by a single filter, applied horizontally and / or vertically, which makes the architecture simple.

Ringing artifacts are removed from a quantized image by an image de-ringing filter that includes a determination unit, an adaptive filter and a nonlinear low-pass filter. The determination unit determines whether each selected pixel of a first set of selected pixels of an image contains a ringing artifact based on, for example, gray-level values of selected pixels within a determination kernel of pixels relating to the selected pixel. The adaptive filter generates a filtered gray-level value for each pixel determined by the determination unit to contain a ringing artifact based on, for example, gray-level values of selected pixels within a filtering kernel of pixels relating to the pixel. The nonlinear low-pass filter generates a low-pass-filtered gray-level value for each selected pixel of a second set of selected pixels of the image.

Disclosed herein are various embodiments of decoding systems and methods. In one embodiment, among others, a decoding system comprises a de-blocking system configured to receive decoded video data and decoding information and remove blocking artifacts from the decoded video data, and a de-ringing system configured to remove ringing artifacts from the de-blocked video data.

A method of post-processing decompressed images includes identification of the direction of an image edge in a pixel block of the image and filtering applied along the boundary of the block in a direction substantially parallel to the detected image edge. Pixels are selected for filtering on the basis of the quantization parameter of the block of which they are members, the relative difference between pixels adjacent to the block boundary, and significant changes value of pixels in a filtering segment. Filtering is applied parallel to the detected edge to protect the sharpness of the edge while reducing or eliminating blocking and ringing artifacts. A method of separately post-processing fields of interlaced video eliminating complications arising from separate compression of the fields is also disclosed.

The invention relates to an angiographic x-ray diagnostic device for rotation angiography with an x-ray emitter which can be moved on a circular path about a patient located on a patient support table, with an image detector unit which can moved on the circular path facing the x-ray emitter, with a digital image system for recording a plurality of projection images by means of rotation angiography, with a device for image processing, by means of which the projection images are reconstructed into a 3D volume image, and with a device for correcting physical effects and / or inadequacies in the recording system such as truncation correction, scatter correction, ring artifact correction, correction of the beam hardening and / or of the low frequency drop for the soft tissue display of projection images and the 3D volume images resulting therefrom.

A filter for post-processing digital images and videos, having an edge mapper, a pixel sorter, and an adaptive filter that simultaneously performs de-ringing and edge sharpening. The combined filter is computationally simpler than known methods and can achieve removal of ringing artifacts and sharpening of true edges at the same time. The present invention also includes a preferred method of simultaneously de-ringing and edge sharpening digital images and videos.

A system and method facilitating progressively transforming and coding digital pictures is provided. The present invention via employment of a multi-resolution lapped transform provides for progressive rendering as well as mitigation of blocking artifacts and ringing artifacts as compared to many conventional compression systems. The invention includes a color space mapper, a multi-resolution lapped transform, a quantizer, a scanner and an entropy encoder. The multi-resolution lapped transform outputs transform coefficients, for example, first transform coefficients and second transform coefficients. A multi-resolution representation can be obtained utilizing second transform coefficients of the multi-resolution lapped transform. The color space mapper maps an input image to a color space representation of the input image. The color space representation of the input image is then provided to the multi-resolution lapped transform. The quantizer receives the first transform coefficients and / or the second transform coefficients and provides an output of quantized coefficients for use by the scanner and / or the entropy encoder. The scanner scans the quantized coefficients in order to produce a one-dimensional vector for use by the entropy encoder. The entropy encoder encodes the quantized coefficients received from the quantizer and / or the scanner resulting in data compression.

Techniques for removing ringing artifacts from video data. A deringing filter in accordance with the present invention preserves real image edges in a video frame, while smoothing out the interiors of objects. In one aspect, a 9-tap low-pass filter is applied to an adaptive processing window. The filter window is initialized with the values in a 3×3 mask centered on the position whose output is computed. Then all values that are very different from the central one are replaced with the central value. The deringing filter varies between 3×3 low-pass and identity, depending on how much the central value differs from its surrounding ones. A deblocking filter in accordance may also be suitably used in conjunction with the deringing filter.

The present disclosure is directed to iterative regularized reconstruction methods. In certain embodiments, the methods incorporate locally-weighted total variation denoising to suppress artifacts induced by PSF modeling. In certain embodiments, the methods are useful for suppressing ringing artifacts while contrast recovery is maintained. In certain embodiments, the weighting scheme can be extended to noisy measures introducing a noise-independent weighting scheme. The present disclosure is also directed to a method for quantifying radioligand binding in a subject without collecting arterial blood. In certain embodiments, the methods incorporate using imaging data and electronic health records to predict one or more anchors, which are used to generate an aterial input function (AIF) for the radioligand.

A method of removing ringing and blocking artifacts from a decompressed digital image. In one method, a background value of the digital image a background region and foreground regions is determined, and a threshold value is computed. A mapping of the digital image is then generated by thresholding the digital image based on the threshold value to produce a thresholded image, and enlarging the foreground regions of the thresholded image to form a map image. The mapping includes the background pixels of the map image. The background region of the decompressed digital image is then cleansed based on the mapping. In an alternate method, ringing artifacts are removed from a decompressed digital image based on a signal-to-noise ratio of the image. In yet another alternate embodiment, ringing artifacts are from a decompressed digital color image that includes a chrominance channel and a luminance channel. An alternate embodiment removes ringing and blocking artifacts.

The invention discloses an improved HEVC sample point self-adaption compensation method. The BO algorithm and the EO algorithm are adopted for performing SAO filtering on images. The sample point self-adaption compensation algorithm is adopted for solving ring effects caused by transform and quantization in the current video coding standard HEVC in the loop filter technology. The current video coding standard HEVC comprises BO and EO algorithms, but sideband distribution conditions are not fully taken into consideration in the BO algorithm which only transmits four continuous sidebands. According to the invention, by use of an image histogram, the sideband distribution conditions can be sufficiently analyzed; intra-frame prediction mode type texture information is extracted in a self-adaption manner; and for different sizes of CTB, four kinds of BO filter modes are added, BO filter pattern discrimination process is improved, and the improved self-adaption compensation method is provided. The experimental results show that compared with the HM10.0, coding performance is improved; bit rate gain of chromaticity can reach -7.53%; and subjective assessment quality of image edge parts is obviously improved.

In some embodiments, the present invention relates to methods or suppressing edge ringing in images. For example, in some embodiments a method of processing an image to suppress ringing and broadened edges induced by image correction processing, includes high-pass filtering a first image to obtain a second image, processing said second image including applying non-linear apodization to said second image to obtain a third image, low-pass filtering said first image to obtain a fourth image, and combining the third image and the fourth image to obtain an output image, wherein the output image is characterized by having reduced edge-response sidelobes as compared to the first images. In some embodiments, the present invention relates to devices comprising means and / or modules to suppress edge ringing in images.

Method and apparatus for improving the quality of super-resolution video imaging by suppressing ringing artifacts, reducing high-frequency noise, reducing blocking artifacts, and smoothing out jagged edges of the image to generate pictures that appear cleaner with less edge degradation. The method operates in a recursive manner within a sequence of low resolution images. Conventional SR processing is primarily enhanced within the invention by adding an artifact suppression section which creates a high frequency component signal ΔSRi having significantly reduced artifacts therein achieving higher quality super-resolution image output. The method can be applied to images and image sequences (video) in monochrome or color and in any desired pixel format. The method can be implemented within image processing devices, in particular those containing programming for executing the described method steps.

In one example of an embodiment of the invention, a method to correct for ring artifacts in an image is disclosed. A first Cartesian image is reconstructed based on data received from an imaging device, and the first Cartesian image is transformed into a first polar image. A first low-pass filter is applied to the first polar image, in the radial dimension, to form a second polar image, and the second polar image is subtracted from the first polar image to generate a third polar image. A second low-pass filter is applied to the third polar image, in an angular dimension, to form a fourth polar image, and the fourth polar image is transformed to Cartesian coordinates to form a second Cartesian image. The first Cartesian image is corrected based, at least in part, on the second Cartesian image.

The present invention refers to 3D rotational X-ray imaging systems for use in computed tomography (CT) and, more particularly, to a fast, accurate and mathematically robust calibration method for determining the effective center of rotation (I) in not perfectly isocentric 3D rotational C-arm systems and eliminating substantially circular ring artifacts (RA) which arise when using such a CT scanner system for acquiring a set of 2D projection images of an object of interest to be three-dimensionally reconstructed. For this purpose, a C-arm based rotational CT scanner comprising at least one radiation detector (D) having an X-radiation sensitive surface exposed to an X-ray beam emitted by at least one X-ray tube (S), each rotating along a non-ideal circular trajectory (TF, TCD) about an object of interest to be three-dimensionally reconstructed from a set of 2D projection images is used for providing geometrical calibration data by scanning a calibration phantom from a plurality of distinct projection directions and calculating, for each projection direction, the 3D positions of the X-ray tube's focal spot and the X-ray detector's center. For approximating the exact 3D position and angular direction of the axis of rotation about which the at least one X-ray tube and the at least one radiation detector rotate, a circular regression technique using a number of mathematically robust least squares fits is applied.

The invention relates to a post-processing method for removing ring artifacts in a CT (computed tomography) image, and the post-processing method comprises the following steps: converting the CT image with ring artifacts from a rectangular coordinate image to a polar coordinate image; extracting the ring image in polar coordinates with a comb filter in a polar coordinate image domain; converting the ring image extracted out of the polar coordinates to a ring image in rectangular coordinates; and subtracting the ring image in the rectangular coordinates from the original CT image with the ringartifacts to obtain a ring-free image. Through frequency domain comb filtering technology, the post-processing method provided by the invention subtracts the corresponding ring artifact image from the original image, without reduction of image resolution and change of quality of the original image. The post-processing method achieves the processing effect, and meanwhile the speed meets product requirements and has space for further optimization, so that the post-processing method is fully suitable for a CT machine with higher requirements for the reconstruction speed.

A system and method facilitating progressively transforming and coding digital pictures is provided. The present invention via employment of a multi-resolution lapped transform provides for progressive rendering as well as mitigation of blocking artifacts and ringing artifacts as compared to many conventional compression systems. The invention includes a color space mapper, a multi-resolution lapped transform, a quantizer, a scanner and an entropy encoder. The multi-resolution lapped transform outputs transform coefficients, for example, first transform coefficients and second transform coefficients. A multi-resolution representation can be obtained utilizing second transform coefficients of the multi-resolution lapped transform. The color space mapper maps an input image to a color space representation of the input image. The color space representation of the input image is then provided to the multi-resolution lapped transform. The quantizer receives the first transform coefficients and / or the second transform coefficients and provides an output of quantized coefficients for use by the scanner and / or the entropy encoder. The scanner scans the quantized coefficients in order to produce a one-dimensional vector for use by the entropy encoder. The entropy encoder encodes the quantized coefficients received from the quantizer and / or the scanner resulting in data compression.

The invention discloses a method for three-dimensional representation of stratified structure micrometer CT imaging of a turbine blade heat barrier coating. The method comprises the following steps: preparing a double-layer-structure heat barrier coating micrometer CT scanning sample; firstly, carrying out micrometer CT scanning on the heat barrier coating sample, carrying out ring artifact and beam hardening correction on projection data, then carrying out three-dimensional reconstruction to obtain three-dimensional stratified structure information, establishing a three-dimensional structure analysis model, and carrying out characteristic segmentation and extraction on three components, namely a ceramic heat insulating layer, a bonding layer and matrix alloy; then, analyzing the thickness of the coating, extracting the distribution of holes in the coating, calculating the porosity, extracting the interface topography of the coating, and analyzing structure characteristics such as internal defects; and finally, estimating the preparation process quality of the heat barrier coating by integrating the composition, thickness, porosity distribution, interface topography and the like. The method for three-dimensional representation of the stratified structure of the heat barrier coating provided by the invention is suitable for estimation and optimization of the spraying process quality of the heat barrier coating, so that the quality of the heat barrier coating can be well controlled.

An imaging technique is disclosed to reduce ringing artifacts from amplitude decay in MR multi-echo acquisition. A flip angle train is determined to match scan parameters for an MR scan to acquire MR data from a given tissue. Reducing the effects of amplitude decay in the echo signal reduces ringing artifacts and thereby improves image quality.

A method and apparatus for ringing artifacts reduction for compressed video signals. The method includes receiving luma data to the digital signal processor, calculating sum of gradient of the luma data; calculating SAD of the luma data; performing pixel classification based of the calculated SAD and sum of gradient, performing erosion on a detected edge pixel indicator on a detected flat pixel indicators, determining at least one of the strength or weakness of the an edge based on the determined edge erosion, performing horizontal dilation on the detected edge pixel indicators and edge strength; and performing at least one of sigma or bilateral filtering to the luma data according to the detected edge pixel indicator, flat pixel indicator, edge strength, the number of very flat pixel in the block.

The invention relates to a ring artifact elimination method for a CBCT image and belongs to the field of medical image processing. According to the invention, firstly, the CBCT image with a ring artifact is transformed from a Cartesian coordinate system to a polar coordinate system; then the CT image P in the polar coordinate system is subjected to smoothing processing by adopting an L0 norm filtering method; next, a smooth image P' obtained after filtering is subtracted from an original image P in the polar coordinate system to obtain an artifact information image Pk with partial original detail information, then the Pk is subjected to extraction and removal of an artifact template by using an OSTU multi-threshold segmentation method and a median method, and the rest of detail information is compensated into the filtered image P'; and finally, the image P' compensated with the detail information is transformed to the Cartesian coordinate system, so that a cone-beam CT image without the ring artifact can be obtained. Compared with the prior art, when detail and edge information in the cone-beam CT image is reserved to the greatest extent, the ring artifact on the CT image, which influences image quality and reality, are effectively removed without obvious residues.

Ringing artifacts in digital images are predicted by determining a number of pixels of a block of pixels exhibiting luminance exceeding a luminance threshold adequate for detecting a ringing artifact and a number of these higher luminance pixels having sufficient contrast with neighbor pixels to be a likely source of a ringing artifact.

Electronic images that are degraded by noise and data reduction, such as MPEG encoding, display artifacts in the reproduced image, such as ringing (“ripples”) and blocks (“huge pixels”), and noise in the image may be apparent as graininess. By performing image analysis, both on a frame-by-frame and pixel-by-pixel basis it is possible to identify and separate edges in the image, ringing artifacts and the boundaries between block transitions. By applying noise reduction according to the analysis, followed by sharpness enhancement, it is possible to clean up the image for further utilization.

The invention proposes a method (FIG. 2) and respective devices (FIG. 2) and software for an algorithm to detect and remove ringing artefacts and mosquito noise in decompressed pictures and video. The proposed idea is based on the observation that ringing is spatially localized within a block, which contains at least a part of an object edge, in particular a strong object edge. Blocks affected by ringing are detected by analyzing (1) a block grid position, location (2) of an object edge and by comparing (7) local spatial activities (Act af, Act nor) of adjacent blocks, i.e. affected blocks and nor) not-affected blocks.

The present invention relates to a method for reducing ringing artifacts of image deconvolution. A deconvolution is applied to the original blurred image and edges are detected within the deconvolved image. Then edge tapering on the original blurred image is performed based on the detected edges.The present invention further relates to a system and a computer program product for reducing ringing artifacts of image deconvolution.

A method of reducing ringing artifacts in a nuclear magnetic resonance measurement is provided. The method utilizes a new pulse sequence that offers ringing cancellation opportunities as well as compensation for otherwise accumulating spin dynamics errors. Ringing cancellation is accomplished by forming linear combinations of spin echoes induced as a result of the pulse sequence. Because the linear combinations are formed between closely spaced spin echoes (i.e., echoes within the same sequence), the likelihood that the ringing artifact will have changed between measurements is diminished.

A method of reducing ring artifacts in tomographic images including providing an original digitized projection measurement comprising a plurality of intensities corresponding to a domain of points on an 2-dimensional grid, operating on said original projection measurement with a filter wherein features of high radial frequency and low angular frequency are attenuated, forming a weighted mixture of said filtered projection measurement and said original projection measurement wherein ring artifacts in said original tomographic image are substantially reduced, and reconstructing the projection measurement to form a tomographic image. Alternatively, a first tomographic image is reconstructed from said original projection measurement, a second tomographic image is reconstructed from said filtered projection measurement, and a weighted mixture is formed from said first tomographic image and said second tomographic image.