Text/line art and halftone discrimination for pixel resolution enhancement

摘要

Text and line art image data is distinguished from halftone image data for selectively enhanced rendering thereof. Specifically, a method of rendering a raster pixel image from a stored bitmap (40, 50) includes (i) determining whether an orphan pixel (54, 58, 140, 146) is detected within a bounded sampling window (52, 56, 122, 124, 126, 128, 130) of the bitmap, and, (ii) processing at least one selected pixel (136) of the bitmap within the sampling window relative to the determining of whether an orphan pixel is detected. In general, an orphan pixel is defined as an isolated white or black pixel in a halftone image. In one embodiment, an orphan pixel (54, 58, 140, 146) is recognized as having a predefined pixel value and as having no other pixels with that value adjacent thereto within the sampling window. In the event an orphan pixel is detected within the window, then the bitmap within the window is determined to be halftone image data and the selected pixel is processed accordingly. In the event an orphan pixel does not exist within the window, then the bitmap within the window is recognized as text or line art image data and processed respectively.