Agfa-gevaert

Agfa Healthcare Nv

Agfa Gevaert Nv

Agfa Healthcare

Other

Agfa Nv

Pieter Paul Vuylsteke

Tom Bertens

Tom Guido Buytaert

Gert Behiels

Emile Paul Schoeters

Walter Jacobs

Piet Dewaele

Joris Soons

Christiaan Fivez

Danny Jozef Janssens

Koen Van De Velde

Lucien Alfred Hayen

Stefan C Van De Velde

Michael Ibison

Frans Dhaenens

Stefan Clemens Van De Velde

Francis Labaere

This invention is related to a multi-scale image processing algorithm for enhancing contrast to noise ratio in an electronic representation of an image represented by a) decomposing said digital image into a set of detail images at multiple resolution levels and a residual image at a resolution level lower than said multiple resolution levels, b) processing said detail images, c) computing a processed image by applying a reconstruction algorithm to the residual image and the processed detail images, said reconstruction algorithm being such that if it were applied to the residual image and the detail images without processing, then said digital image or a close approximation thereof would be obtained. The processing comprises the steps of: d) calculating a local variance value for at least one detail image pixel within a neighbourhood of said detail image pixel; e) enhancing or suppressing at least one detail image pixel as a function of said local variance value and said detail image pixel value.

Method and apparatus for noise reduction

A multi-scale image processing algorithm for enhancing contrast in an electronic representation of an image represented by a) decomposing said digital image into a set of detail images at multiple resolution levels and a residual image at a resolution level lower than said multiple resolution levels, b) processing at least one pixel of said detail images, c) computing a processed image by applying a reconstruction algorithm to the residual image and the processed detail images, said reconstruction algorithm being such that if it were applied to the residual image and the detail images without processing, then said digital image or a close approximation thereof would be obtained. The processing comprises the steps of: d) calculating for said pixel, at least one statistical measure for two or more translation difference image pixel values within a neighbourhood of said pixel; and e) modifying the value of said pixel of said detail images as a function of said statistical measure and said value of said pixel of said detail images.

Method and apparatus for contrast enhancement

In a method to enhance the contrast of spatially-localized phenomena in an image such as microcalcifications in a mammogram, a multi-scale decomposition is applied to a digital signal representation of the image thereby generating a number of detail images at different scales, the detail signals pertaining to the spatially-localized phenomena having a common polarity (either negative or positive) being modified at at least one scale.

Method and system for enhancing contrast of spatially-localized phenomena in mammography image

A method of generating a multiscale contrast enhanced image is described wherein the shape of edge transitions is preserved. Detail images are subjected to a conversion, the conversion function of at least one scale being adjusted for each detail pixel value according to the ratio between the combination of the enhanced center differences and the combination of the unenhanced center differences. Several adaptive enhancement measures are described.

Method of enhancing the contrast of an image

At least one of two enhancement methods for changing contrast and/or density are applied to an image. According to a first enhancement method the window width/level settings of the image are modified and according to a second enhancement method density and contrast of the image are modified by modifying a multi-scale representation of the image whereby modification is derived from at least two gradient functions determined at different scales, a gradient function at a specific scale specifying the dependency of contrast amplification at said scale as a function of density. The amount of modification obtained by applying either of said first and second enhancement methods is determined by the amount of movement of at least one indicium.

Method and system for changing image density and contrast

At least one approximation image is created of the image at one or multiple scales. Translation difference images are created by pixel-wise subtracting the values of an approximation image at scale s and the values of a translated version of the approximation image. A non-linear modification is applied to the values of the translation difference image (s) and at least one enhanced center difference image at a specific scale is computed by combining the modified translation difference images at that scale or a smaller scale with weights W. An enhanced image is computed by applying a reconstruction algorithm to the enhanced center difference images. The non-linear modification of the values of the translation difference images is steered by the values of an orientation map which comprises for each pixel a local direction of interest. In addition or alternatively, at least one enhanced center difference image is computed by anisotropic weighing of the enhanced translation differences with weights steered by the orientation map.

Method of generating a multiscale contrast enhanced image

A digital image signal is decomposed into a multi-scale representation comprising detail images and approximation images. Translation difference images are computed by subtracting an approximation image at scale s and a translated version of that approximation image. The values of the translation difference images are non-linearly modified. An amplification image is computed at least one scale as the ratio of a first image being computed by combining the modified translation difference images at the same or smaller scale and a second image created by combining unenhanced translation difference images at the same or smaller scale. Next, an enhanced multi-scale detail representation is computed by modifying at least one scale the detail image according to the amplification image at that scale. An enhanced image representation is computed by applying a reconstruction algorithm to the enhanced multi-scale detail representation. The non-linear modification of the values of the translation difference image is steered by the values of an orientation map which comprises for each pixel on a specific scale a local direction of interest.

At least one approximation image is created of the image at one or multiple scales. Translation difference images are created by pixel-wise subtracting the values of an approximation image at scale s and the values of a translated version of the approximation image. A non-linear modification is applied to the values of the translation difference image (s) and at least one enhanced center difference image at a specific scale is computed by combining the modified translation difference images at that scale or a smaller scale with weights w. An enhanced image is computed by applying a reconstruction algorithm to the enhanced center difference images. The non-linear modification of the values of the translation difference images is steered by (a) characteristic (s) computed out of the approximation image (s) at least one scale.

A method of generating a multiscale contrast enhanced image is described wherein the shape of edge transitions is preserved. Detail images are subjected to a conversion, the conversion function of at least one scale being adjusted for each detail pixel value according to the ratio between the combination of the enhanced center differences and the combination of the unenhanced center differences.

Method of generating multiscale contrast enhanced image

A method of generating a multiscale contrast enhanced image preserving the shape of the edge transitions is described. Enhanced detail pixel values are computed by combining enhanced center difference images at least one scale.

A short-time Goertzel transform is applied to the image signal to transform it into a representation of the spatial frequency component corresponding to the periodic pattern. This representation is processed. Next the inverse of the transformation is computed and the result of the inverse transformation is removed from the image signal.

Method of suppressing a periodical pattern in an image

A method of generating a contrast enhanced version of a grey value image by applying contrast amplification to a multiscale representation of the grey value image wherein density in the contrast enhanced version as a function of grey value and contrast amplification are specified independently.

Multiscale gradation processing method

The contrast of an image is enhanced by converting pixels of detail images of a multi-scale digital representation of the image according to a conversion function. The conversion function is monotonically increasing and odd and provides maximum amplification within an intermediate subrange of pixel values of a detail image which subrange is considered critical. Furthermore the slope of the conversion function has a local maximum and a local minimum.

Method for enhancing the contrast of an image

A digital signal representation of an image is normalized by applying a normalization parameter to all pixels of the digital signal representation of the image or to the pixels of a multi-scale representation of the image. The normalization parameter can be derived from the digital signal representation itself or from a multi-scale representation of the image. Different criteria for deriving the normalization parameter are disclosed.

Method of normalising a digital signal representation of an image

An image which has been subjected to image processing wherein contrast amplification and density can be specified independently is displayed on a display screen. An initial density level is specified. The contrast of pixels in the displayed image having a density substantially equal to the specified initial density is changed upon movement of an indicium in a first direction and the density of pixels in the displayed image having a density substantially equal to the specified initial density is changed upon movement of the indicium in a second direction.

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Mortsel, Belgium

Pieter Paul Vuylsteke