US 5,293,579 AGranted

Method and apparatus for smoothing jagged edges in a graphics display

AssigneeRay Dream, Inc.

InventorJohn F. Stockholm

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Abstract

A method and apparatus for detection and smoothing of jagged edges in a graphics display is described. The edge detection and smoothing is done using only a pixel-map representation of the pixel colors of the image as input. Edges are detected based upon the color representations of certain groups of pixels. Smoothing of the edges is accomplished by adjusting the color of certain pixels in the region of a detected edge. Edges are detected by successively scanning either sets of two rows or sets of two columns of pixels. Edge detection occurs during the row or column scans by discerning certain sequences of color changes between pairs of adjacent pixels. Color changes are detected only if certain threshold changes in color occur between pairs of adjacent pixels. Unless the threshold color change is exceeded, pixels are considered to be the same color and no edge is detected. Jagged edges are detected and smoothed regardless of the type of color representation used in the pixel-map. The pixel-map may represent, for instance, the color of each pixel as a combination of shades of red, green or blue, a combination of varying degrees of hue, brightness and saturation, or some other combination.

Claims6

Dependent claims

A method for detecting jagged edges in an image represented by a rectangular array of pixels, the method comprising the steps of:

accessing a first group of pixel data from a data storage device, the first group of pixel data comprising a first set of pixel data and a second set of pixel data, wherein:
the first and second sets of pixel data are successive sets of pixel data from adjacent columns or adjacent rows;
and
the successive sets of pixel data comprise pixel data for two adjacent pixels in each row or column;
determining a first difference between the value of the pixel data for a first pixel of the first set and the value of the pixel data for a first pixel of the second set;
determining a second difference between the value of the pixel data for a second pixel of the first set and the value of the pixel data for a second pixel of the second set;
determining, based upon the comparison of the first and second sets of pixel data, whether a jagged edge is present in the image;
accessing a second group of pixel data from the data storage device, the second group of pixel data comprising a third set of pixel data and a fourth set of pixel data, wherein:
the third and fourth sets of pixel data are successive sets of pixel data from adjacent columns or adjacent rows;
and
the successive sets of pixel data comprise pixel data for two adjacent pixels in each row or column;
determining a third difference between the value of the pixel data for a first pixel of the third set and the value of the pixel data for a first pixel of the fourth set;
determining a fourth difference between the value of the pixel data for a second pixel of the third set and the value of the pixel data for a second pixel of the fourth set;
and
determining, based upon the comparison of the first and second sets of pixel data, and the comparison of the third and fourth sets of pixel data, the type of jagged edge present in the image.

12 more elements

A system for detecting jagged edges in an image represented by a rectangular array of pixels, the system comprising:

means for accessing a first group of pixel data from a data storage device, the first group of pixel data comprising a first set of pixel data and a second set of pixel data;
the first and second sets of pixel data are successive sets of pixel data from adjacent columns or adjacent rows;
and
the successive sets of pixel data comprise pixel data for two adjacent pixels in each row or column.
means for determining a first difference between the value of the pixel data for a first pixel of the first set and the value of the pixel data for a first pixel of the second set;
means for determining a second difference between the value of the pixel data for a second pixel of the first set and the value of the pixel data for a second pixel of the second set;
means for determining, based upon the comparison of the first and second sets of pixel data, whether a jagged edge is present in the image;
means for accessing a second group of pixel data from the data storage device, the second group of pixel data comprising a third set of pixel data and a fourth set of pixel data, wherein:
the third and fourth sets of pixel data are successive sets of pixel data from adjacent columns or adjacent rows;
and
the successive sets of pixel data comprise pixel data for two adjacent pixels in each row or column
means for determining a third difference between the value of the pixel data for a first pixel of the third set and the value of the pixel data for a first pixel of the fourth set;
and
means for determining a fourth difference between the value of the pixel data for a second pixel of the third set and the value of the pixel data for a second pixel of the fourth set;
and
means for determining, based upon the comparison of the first and second sets of pixel data, and the comparison of the third and fourth sets of pixel data, the type of jagged edge present in the image.

13 more elements

Dependencies are inferred from the claim text.