Apple Inc.

Other

Kok S Chen

Gabriel G Marcu

Magnus L Karlsson

Riaz A Moledina

Allen M Chan

Kevin W Andresen

Mark Zimmer

Randall G Guay

Marilyn Chen

Hungviet H Nguyen

Ralph T Brunner

Thomas Chan

Steve Swen

Stuart L Claassen

Wei Chen

John Harper

Peter N Graffagnino

Michael D Stokes

Jose Olav Andrade

Iue-Na Swen

John Z Z Zhong

David D Barnes

Methods and apparatuses for color correction that includes gamma correction. One embodiment of the present invention pre-processes the native device information of a color device (e.g., a color display device) to generate pseudo-native device information such that when a single, unique function is applied on the pseudo-native device information, a customized look up table for gamma correction in a video card is generated. The customized look up table is calibrated for the optimization of color rendering for skin tone in one region in a color space while maintaining the gray colors for the user interface elements in another region in the color space.

Method and apparatus for improved color correction

A system and method for performing Bayer reconstruction of images using a programmable graphics processing unit (GPU) are described herein. A Bayer filtered image in RAW format is uploaded to the GPU, unpacked, and reconstructed. Optionally, the reconstructed image may be transformed into any desired color space and/or displayed by a video card in which the GPU resides. The reconstruction is performed independently on each of the red, blue, and green image fields. The red and blue image fields are reconstructed using first and second interpolation passes in first and second orthogonal directions. Each reconstruction pass preferably employs a two-lobed Lanczos filter. The green image field is interpolated using a single interpolation pass in a direction diagonal to the first and second orthogonal directions, and preferably employs a box filter.

Bayer reconstruction of images using a GPU

Methods and apparatuses for color correction of color device for various operating conditions. In at least one embodiment of the present invention, operating under a current condition, a color correction operation that is derived from color correction operations defined for other conditions is performed on the color data. In another embodiment, a device profile for managing colors for a color device operating under one condition is interpolated from the device profiles for the color device operating under other conditions (e.g., based on the input received from a user interface according to the perception of the user or based on the measurement of a sensor). The interpolation can be based on the input received from a user interface according to the perception of the user or it can be based on the measurement of a sensor or a set of sensors. Various operating conditions for a color device (e.g., a scanner, a camera, a video camera, a printer, a display device such as a CRT monitor or an LCD display panel, a television set, or others) include chromaticity and illumination of ambient light, background color for a display device, characteristics of print media for a printer, humidity, temperature, pressure and ink level for an ink jet printer, the age of a light source for a scanner, and others.

Method and apparatus for color correction of color devices for various operating conditions

White point is corrected without degrading luminance on a display device. A white point manager modifies the balance between red, green and blue according to a target white point up to a threshold gray value. As the gray scale approaches white from the threshold gray value, the white point manager blends the balance between red, green and blue from the target white point substantially towards the native white point for the display device, so as not to degrade luminance as the gray scale approaches white.

Luminance point correction without luminance degradation

Undesirable artifacts appearing in color images, such as blooming or smudging around the edges of text, are avoided through selective reduction of the color gamut for objects which form the image. Individual component color values are modified by taking into account combinations of colors and their effect upon the artifacts to be eliminated. Only those parameter values which contribute to the artifact are modified. Other parameter values are left intact, to maintain the original image characteristics. When a color value is modified, all components of that color are modified in a symmetrical manner, to preserve the hue of the original color. The impact on the image is further minimized by selectively applying color correction only to those objects in which the artifact is pronounced.

Conversion of output device color values to minimize image quality artifacts

A method, device and computer system for creating a smooth, continuous height (scalar or vector) field are described. The described techniques permit arbitrary closed regions to be smoothly shaded without producing unnatural smoothness at the region's edges or boundaries.

Manipulating text and graphic appearance

Successive frames or images of an input image that are presented to the output device are individually halftoned. A starting location within the input image for tiling one of one or more halftone techniques over the frame or image is determined. The starting location is then offset from the previously used starting location after a certain number of frames or images have been halftoned. Any halftoning technique may be used to halftone the frames or images. The halftoned frames or images are then viewed in a sequence in time.

System and method for halftoning using a time-variable halftone pattern

Methods and apparatuses for performing gamma corrections to maintain a plurality of colors substantially consistent with a color point. In one aspect of the present invention, a method to generate correction functions for performing color correction for a device for signals of different color components in a color space includes: generating a first correction function for a first color component in the color space; and generating second correction functions for second color components in the color space by reducing first color differences between a target White point and white points of a plurality of grays corrected by the first and second correction functions. The second color components are the color components in the color space other than the first color component. The first color differences are minimized relative to a chromaticity diagram.

A Gaussian blur approximation is applied to an image by repeated down-sampling operations followed by an up-sample operation. By using a truncated Gaussian filter as the down-sample filter, the frequency spectrum removed during down-sampling operations closely approximates the frequency spectrum lost during a true Gaussian blur operation. While any 'good' up-sample filter may be used, up-sampling via linear interpolation may be especially beneficial in systems having a dedicated graphics processing unit. One benefit of the described technique is that it is computationally less costly to implement than a Gaussian blur. Another benefit is that this computational benefit increases as the size of the blur increases&#x2014;becoming significant even for small blurs. Yet another benefit of the invention is that a judicious selection of pixel address to convolve with the filter leads to substantially reduced number of texture lookups required to effect a convolution.

Gaussian blur approximation suitable for GPU

The present invention overcomes the limitations of the prior art by providing a system and method for halftoning using time-variable halftone patterns. Successive frames that are presented to the output device are individually halftoned. The halftone pattern is changed from frame to frame. The different halftone patterns can be generated in real time, or they can be calculated prior to halftoning and stored in memory. Additionally, the halftone patterns can be generated using any conventional halftoning technique. The same halftoning technique can used to create each halftone pattern, or the halftoning techniques can be varied when creating halftone patterns. The halftoned frames are then viewed in a sequence in time. Because the halftone pattern is changing from frame to frame, the visibility of the pattern is reduced when compared with the patterns produced by prior art halftoning methods.

White point correction without luminance degradation

A method and apparatus is described for providing a consistent visual appearance of pixels of a display screen with respect to a viewing position. Variations between perceived pixel level values associated with the pixels and corresponding pixel level values may be compensated for. Variations are associated with a viewing angle between pixel location and the viewing position and compensated for by applying a respective different correction factor to each of the corresponding pixel level values based on a respective viewing angle. Accordingly different non-linear correction curves corresponding to locations may be established relating a range of pixel level values to a corresponding range of corrected pixel level values associated with the viewing position. A calibration pattern may be further be displayed and user inputs associated with locations received responsive to calibration pattern. Viewing position and non-linear correction curves may thereby be established for locations relative to the viewing position and based on user inputs. User inputs are stored with an association to a user identity. A user input is processed to obtain user identity and stored user inputs and viewing position and non-linear correction curves established based on the user inputs. Change is detected in a relative orientation between a display orientation and the viewing position and a second respective different correction factor applied to each corresponding pixel level value based on the change. Second different non-linear correction curves are established relating pixel level values to corrected values associated with relative orientations. Interpolation or an analytical function is applied to arrive at corrected pixel values. To detect changes, one or more sensors are read. A viewing position sensor senses the position of a remote device coupled to the viewer. The viewer feature tracking sensor includes a camera and means for analyzing an image for features associated with the viewer.

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Sunnyvale, CA, United States of America

Kok S Chen