INPUT OF CONTROL INFORMATION TO AN ELECTRONIC IMAGE SCANNER THROUGH THE IMAGING APPARATUS
Original Publication Date: 1990-Aug-31
Included in the Prior Art Database: 2004-Apr-05
Xerox Disclosure Journal
In conjunction with an image scanning device, various image processing functions are available for altering the appearance of the document image acquired at the scanning array. Two particularly common functions are screening and thresholding. Data is initially derived in an analog form, and then converted to a digital value. Then, thresholding functions typically compare the image data with a uniform level across an image, to provide a binary output from the digital image data. Varying the threshold level varies the contrast of the image. Screening is a similar function, used to simulate gray levels within an image. Over a unit area of several pixels in the image, a series of threshold levels are applied to the image data so that a binary output is still produced, but varying over the unit area, depending on the density of the level of grey in the original image. Different screens apply different patterns of threshold levels to achieve different effects. It is highly desirable to provide a plurality of threshold levels and screens in a scanning device. The application of screens and thresholds to image data, as well as the types of screens is well known.