Methods for generating anti-aliased text and line graphics in compressed document images

An image rendering method comprising:

• scanning an image to obtain scanned high resolution image data including text or lineart data;
• generating an anti-aliased grayscale version of the text or lineart data by
• separating the pixels of the image data into boundary pixels and non-boundary pixels by identifying any pixel in the image data having at least one of the eight nearest neighboring pixels being of an opposite color, the boundary pixels including both ON and OFF pixels;
• separating the identified boundary pixels into interior boundary ON pixels and exterior boundary OFF pixels;
• separately determining and setting a grayscale value for the interior boundary ON pixels and the exterior boundary OFF pixels;
• and
• rendering the image using the determined grayscale pixel values for the interior boundary ON pixels and the exterior boundary OFF pixels.

The image rendering method of claim 30, wherein:

• scanning the image comprises producing high resolution grayscale data;
• and
• generating the anti-aliased grayscale version of the text or lineart data further comprises:
• individually deriving values of grayscale boundary pixels using the high resolution grayscale data, and
• storing the individually derived values of the grayscale boundary pixels.

An image rendering system comprising:

• a scanner that scans an image and produces image data and high resolution binary data;
• an encoder that is coupled to the scanner and encodes the image data to provide encoded image data including anti-aliased grayscale text or lineart data that includes an identification of boundary pixels and associated pixel values, wherein the encoder separates the boundary pixels into interior boundary pixels and exterior boundary pixels;
• and
• a decoder that is coupled to the encoder and decodes the encoded image data to provide decompressed data including anti-aliased text or lineart data and renders the decompressed data, wherein the decoder stores default global grayscale values including first and second default global grayscale values and sets the interior boundary pixels to the first default global grayscale value and sets the exterior boundary pixels to the second global default grayscale value.

An image rendering method comprising:

• scanning an image to obtain scanned image data including text or lineart data, wherein scanning the image produces high resolution grayscale data;
• generating an anti-aliased grayscale version of the text or lineart data, comprising:
• separating the grayscale pixels of the high resolution grayscale data into boundary pixels and non-boundary pixels,
• individually deriving values of grayscale boundary pixels using the high resolution grayscale data, and
• storing the individually derived values of the grayscale boundary pixels, including compressing the individually derived values of the grayscale boundary pixels as part of a set of grayscale tokens that represent connected components in a foreground image that is part of the scanned image data;
• and
• rendering the image using the individually derived pixel values.