Abstract: A method, system and reference target for estimating spectral data on a selected one of three spectral information types is disclosed. Spectral information types comprise illumination of a scene, spectral sensitivity of an imager imaging the scene and reflectance of a surface in the scene. The method comprises obtaining a ranking order for plural sensor responses produced by the imager, each sensor responses being produced from a reference target in the scene, obtaining, from an alternate source, data on the other two spectral information types, determining a set of constraints, the set including, for each sequential pair combination of sensor responses when taken in said ranking order, a constraint determined in dependence on the ranking and on the other two spectral information types for the respective sensor responses and, in dependence on the ranking order and on the set of constraints, determining said spectral data that optimally satisfies said constraints.

Abstract: A method and system for producing accented image data for an accented image is disclosed. The method includes decomposing each of a first and a second image into a gradient representation which comprises spectral and edge components. The first image comprises more spectral dimensions than the second image. The edge component from the first image is combined with the spectral component from the second image to form a combined gradient representation. Accented image data for the accented image is then generated from data including the combined gradient representation.

Abstract: Methods to generate, and devices to use, an adaptive tone curve generation operation are disclosed. Tone curves so generated have been found to produce stable tone mapping in a wide range of operational environments, including during multi-exposure fused images (e.g., during high dynamic range image fusion). In general, techniques are disclosed that use a content-load histogram in combination with image capture device noise information to adaptively bound a tone curve's slope and, therefore, the resulting tone curve. As used here, a content-load histogram is a histogram that captures spatial, color or other information carried by an image's pixels at various gray levels.

Abstract: Systems and methods for generating local image statistics are provided. In one example, an image signal processing system may include a statistics pipeline with image processing logic and local image statistics collection logic. The image processing logic may receive and process pixels of raw image data. The local image statistics collection logic may generate a local histogram associated with a luminance of the pixels of a first block of pixels of the raw image data or a thumbnail in which a pixel of the thumbnail represents a downscaled version of the luminance of the pixels of the first block of the pixel. The raw image data may include many other blocks of pixels of the same size as the first block of pixels.

Abstract: Systems and methods for local tone mapping are provided. In one example, an electronic device includes an electronic display, an imaging device, and an image signal processor. The electronic display may display images of a first bit depth, and the imaging device may include an image sensor that obtains image data of a higher bit depth than the first bit depth. The image signal processor may process the image data, and may include local tone mapping logic that may apply a spatially varying local tone curve to a pixel of the image data to preserve local contrast when displayed on the display. The local tone mapping logic may smooth the local tone curve applied to the intensity difference between the pixel and another nearby pixel exceeds a threshold.

Abstract: Methods, systems, and apparatus, including computer programs encoded on computer storage media, are described for transforming an image at least in part by using a gamma transformation that maximizes information in the transformed image. In one aspect, a digital image is received and brightness of the digital image is determined. The brightness of the digital image can include luminance or color. Maximum available detail in the digital image is brought out at least in part by applying to the brightness of the digital image a first gamma exponent that is equal to one divided by a negative of an average logarithm of the brightness of the digital image.

Abstract: A color image comprises color values in each of one or more color channels for each of a plurality of points, or pixels, within the image. The image is represented by rank ordering the values in each color channel. The image representation generated in this way is usable for automated-vision or computer-vision tasks, for example.

Abstract: A method and system for producing a scalar image from a derivative field and a vector image is disclosed. A function class c is selected, where all members of the class c are functions which map each vector of the vector image to a unique scalar value. A function f is selected from the class c which maps the vector image to a scalar image, the derivative of which is closest to the derivative field. The scalar image is generated from the vector image by using f to calculate each scalar value in the scalar image from a corresponding vector in the vector image.

Abstract: A method of estimating, illuminant comprises minimizing a Minkowski norm with illuminant constraints. The norm is preferably between 3 and 7 and most preferably between 4 and 6. The method is used to remove the color of an illuminant from an image.

Abstract: A colour image comprises colour values in each of one or more colour channels for each of a plurality of points, or pixels, within the image. The image is represented by rank ordering the values in each colour channel. The image representation generated in this way is usable for automated-vision or computer-vision tasks, for example.

Abstract: Methods, systems, and apparatus, including computer programs encoded on computer storage media, are described for transforming an image at least in part by using a gamma transformation that maximizes information in the transformed image. In one aspect, a digital image is received and brightness of the digital image is determined. The brightness of the digital image can include luminance or color. Maximum available detail in the digital image is brought out at least in part by applying to the brightness of the digital image a first gamma exponent that is equal to one divided by a negative of an average logarithm of the brightness of the digital image.

Abstract: A color image comprises color values in each of one or more color channels for each of a plurality of points, or pixels, within the image. The image is represented by rank ordering the values in the or each color channel. The image representation generated in this way is usable for automated-vision or computer-vision tasks, for example.

Abstract: A method and system for producing accented image data for an accented image is disclosed. The method includes decomposing each of a first and a second image into a gradient representation which comprises spectral and edge components. The first image comprises more spectral dimensions than the second image. The edge component from the first image is combined with the spectral component from the second image to form a combined gradient representation. Accented image data for the accented image is then generated from data including the combined gradient representation.

Abstract: In a method for the recovery of an invariant image from a 3-band colour image, information relating to the angle for an “invariant direction” in a log-chromaticity space is obtained on the basis that the correction projection is that which minimizes entropy in the resulting invariant image. The method is applied to remove shadows from unsourced imagery.

Abstract: An image signal is processed by deriving measurements representing the luminance of a signal; calculating values relating to the local mean, the local standard deviation, the local maximum and/or the local minimum; and computing therefrom local standard coordinates such as z-scores which are independent of brightness and contrast.

Abstract: A method of estimating, illuminant comprises minimising a Minkowski norm with illuminant constraints. The norm is preferably between 3 and 7 and most preferably between 4 and 6. The method is used to remove the colour of an illuminant from an image.

Abstract: A method of adjusting the N components of an N component color signal (such as the 3 components of an RGB color signal) with respect to color temperature of illuminating light when imaging a colored subject, comprising the step of computing the difference between each of the components of the color signal for different temperatures of illuminating light, using an algorithm based on the spectral sensitivity of the imaging means and Planck's equation defining black body illumination to obtain N components whose values are independent of the color temperature of the illuminating light. Normalisation of the adjusted values renders the values independent of intensity of illumination and can also reduce the processing time for further processing of the signals. A technique for compensating for gamma correction which is commonly built in cameras, is disclosed.

Abstract: An image signal is processed by deriving measurements representing the luminance of a signal; calculating values relating to the local mean, the local standard deviation, the local maximum and/or the local minimum; and computing therefrom local standard coordinates such as z-scores which are independent of brightness and contrast.

Abstract: An image recording apparatus for processing an image includes a camera (10), or other optical sensor means, for recording a first digital optical image of at least part of a scene illuminated by an illuminant light and for recording a second digital optical image of at least a part of substantially the same scene under substantially the same illuminant light. The images may be recorded on respectively different sensor arrays (12a and 12b). The light producing the first and second images undergoes different optical processing in order to produce those images, and processing means (18) in communication with the optical sensor means is provided for processing information relating to the first and second images. By relating the two images, the processing means (18) is able to provide information regarding the color of the illuminate light or other physical properties of the illuminated scene.

Abstract: A colour image comprises colour values in each of one or more colour channels for each of a plurality of points, or pixels, within the image. The image is represented by rank ordering the values in the or each colour channel. The image representation generated in this way is usable for automated-vision or computer-vision tasks, for example.