Adaptive enlarging and/or sharpening of a digital image
OwnerDavid R. Popeinventor
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Abstract
The invention relates to enlarging and/or sharpening a digital input image into a resized and/or sharpened digital output image, where the enlargement technique is performed in accordance with the input image content. An enlarged approximated version of an original image is combined with a residual image to produce an output image of desired size. The approximated image is computed by a two-dimensional (2-D) approximation. The residual image is the same size as the original image, or may be enlarged to the size of the desired output image. The residual image data is selectively added to the approximated image such that image information is added everywhere in the image except at continuous edges.
Claims44
A computer method of producing an resized output image from an original input image comprising digital pixel data, the method comprising:
- (a) computing an approximated image using a two-dimensional approximation technique applied to the digital pixel data of the original input image;
- (b) determining a residual image;
- (c) determining a weighting factor for each pixel of the approximated image;
- and
- (d) selectively adding residual image data into the approximated image in accordance with the weighting factor for each resized output image pixel.
A method of suppressing overshoots or undershoots resulting from sharpening an original image comprised of digital pixel data comprising:
- (a) sharpening the original input image;
- (b) for each pixel in the original input image (unsharpened) finding the maximum and minimum pixel intensity value in an area surrounding the pixel, wherein the area to be searched covers the range of any overshoot or undershoot due to the sharpening method;
- (c) for each sharpened pixel, comparing the intensity value of the sharpened pixel to the corresponding maximum and minimum values found in (b) and if the value of the sharpened pixel is outside the range of said maximum and the minimum, modifying the sharpened value to be closer to or equal to the nearer of the maximum or the minimum.
A method of sharpening an original image of digital pixel data, the method comprising:
- (a) determining the pixels in the original input image to be sharpened;
- (b) for any pixel to be sharpened, searching an area around the pixel to be processed in the original input image for the maximum and minimum pixel values;
- and
- (c) using a non-linear but continuous function, computing a sharpened pixel value that is closer to the nearer of the maximum or minimum value found in (b) for each pixel.
A method of distinguishing between texture, continuous edges, and smooth regions in an image of digital pixel data using local gaussian curvature in the image, the method comprising:
- (a) computing the gaussian curvature at each pixel location;
- and
- (b) determining pixels within the image that are likely to be texture, in accordance with the computed gaussian curvature and processing such that high gaussian curvature indicates texture and not continuous edges or smooth regions.
An apparatus that processes digital image data, the apparatus comprising:
- a memory;
- and
- a processor that receives the digital image data, comprising pixel data that defines an original input image, from the memory and produces an enlarged image corresponding to the input image by computing an approximated image using a two-dimensional approximation technique applied to the digital pixel data of the original input image, determining a residual image, determining a weighting factor for each pixel of the approximated image, and selectively adding residual image data into the approximated image in accordance with the weighting factor for each enlarged output image pixel.
An apparatus that processes digital image data, the apparatus comprising:
- a memory;
- and
- a processor that receives the digital image data, comprising pixel data that defines an original input image, from the memory and suppresses overshoots or undershoots by sharpening the original input image, for each pixel in the original input image (unsharpened) finding the maximum and minimum pixel intensity value in an area surrounding the pixel, wherein the area to be searched covers the range of any overshoot or undershoot due to the sharpening method, for each sharpened pixel, comparing the intensity value of the sharpened pixel to the corresponding maximum and minimum values and, if the value of the sharpened pixel is outside the range of said maximum and the minimum, modifying the sharpened value to be closer to or equal to the nearer of the maximum or the minimum.
A digital image processing apparatus for processing a digital input image into an output image, the apparatus comprising:
- an input buffer that stores pixel data of the input image;
- locating means for locating a local position with the input image for interpolation;
- approximated image means for obtaining a first approximated output image pixel at a predetermined pixel position in an approximated output image;
- residual image means for obtaining a residual image pixel at the predetermined pixel position;
- means for deriving an input image characteristic value from the input image pixel data;
- and
- means for calculating a resultant output image pixel at the predetermined position in the output image by combining the approximated and residual image pixels as a function of the input image characteristic value.
Dependencies are inferred from the claim text.