Apparatus and method for adaptively interpolating a full color image utilizing luminance gradients
AssigneeEastman Kodak Company
InventorRobert H. Hibbard
Life of this patent
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Abstract
Adaptive interpolation is performed by apparatus operating upon a digitized image signal obtained from an image sensor having color photosites that generate a plurality of color values, but only one color per photosite. A digital processor obtains gradient values from the differences between luminance values in vertical and horizontal image directions. The gradient values are compared to a programmable threshold in order to select one of the directions as the preferred orientation for the interpolation of additional luminance values. The interpolation is then performed upon values selected to agree with the preferred orientation.
Claims8
Apparatus for processing a digitized image signal obtained from an image sensor having color photosites that generate a plurality of color values, but only one color value for each photosite location, said apparatus comprising:
- means for storing the digitized image signal as a pattern of luminance and chrominance values, wherein some photosite locations lack luminance values;
- a processor operative with said storing means for generating an additional luminance value missing from a photosite location by the interpolation of the additional luminance value for such locations from luminance values at nearby photosite locations, said processor including
- means for generating gradient values from the differences between luminance values in at least two image directions;
- means for comparing the gradient values to one or more thresholds;
- means responsive to the threshold comparison for selecting one of said at least two image directions as a preferred orientation for the interpolation of the additional luminance value;
- and
- means for interpolating the additional luminance value from luminance values selected to agree with the preferred orientation.
A method for interpolating missing luminance values from a digitized image signal obtained from a color image sensor having photosites that generate a pattern of actual luminance and chrominance values, one actual value for each photosite location, said method comprising the steps of:
- obtaining gradient values from the differences between actual luminance values in vertical and horizontal image directions;
- comparing the gradient values to a predetermined threshold;
- selecting the image direction, in which the comparing step indicates scene structure, for the interpolation of the missing luminance values;
- and
- interpolating each missing luminance value from actual luminance values at nearby locations corresponding with the selected direction, and thereby with the scene structure.
Dependencies are inferred from the claim text.