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Rule for the Selection of Double-Dotting Location

IP.com Disclosure Number: IPCOM000061288D
Original Publication Date: 1986-Jul-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 3 page(s) / 54K

Publishing Venue

IBM

Related People

Czyszczewski, JS: AUTHOR [+3]

Abstract

A method is described for preventing background stripes in text printed on a serial printer. Serial printers print a horizontal row of data, then index and print the next horizontal row of data. How well the two rows of data line up is dependent on the index accuracy. If the index does not go far enough, there is a slight overlap between the two rows of print. If the index goes too far, then there is a space between the lines. If the two lines were supposed to come together, as in a drawing rule, then a slight overlap will hardly be noticeable because the print is the same color. However, extra space will look like a stripe of the paper color showing through. The term "drawing rule" is an instruction to draw a vertical or horizontal line of specified width.

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Rule for the Selection of Double-Dotting Location

A method is described for preventing background stripes in text printed on a serial printer. Serial printers print a horizontal row of data, then index and print the next horizontal row of data. How well the two rows of data line up is dependent on the index accuracy. If the index does not go far enough, there is a slight overlap between the two rows of print. If the index goes too far, then there is a space between the lines. If the two lines were supposed to come together, as in a drawing rule, then a slight overlap will hardly be noticeable because the print is the same color. However, extra space will look like a stripe of the paper color showing through. The term "drawing rule" is an instruction to draw a vertical or horizontal line of specified width. The term "double-dotting" is sometimes referred to as pel-extension. In the printing of text, print speed is important. Therefore, the solution needs to be one which does not degrade performance by using up excessive processing time. The method used by some prior-art systems is to have the hardware duplicate the row of dots on the bottom of the swath of print (or on the top of the swath of print). "Duplicate" means to make the height of the data printed one pel larger than the data sent by the software to the hardware. The new pel comes from copying the bottom (or top) bit sent by the software to a new bottom (or top) pel. In the case of overshoot, there is no gap in the printed data even though the index leaves a whole pel's worth of space between the data provided by the software, since the added bits fill in the gap. In the cases of no position error and of undershoot, some of the pels overlap, but since text or rules are always printed in one color, the printed color will be correct and the increased darkness of the print will not be nearly as objectionable as a stripe of paper showing through. After some thought, it may appear to not make any difference if the top pel or the bottom pel is duplicated. Certain factors need to be considered to determine which pels should be duplicated, such as the direction of printing and the type of algorithm for print data selection since pels can be duplicated on the top of the row of data provided by the software or on the bottom. Consider the case illustrated in Fig. 1 where there are two characters that are nearly an entire swath high and a vertical rule that is more than two swaths high. The two A's must be printed by a single swath so that the characters are not divided between swaths. However, part of the rule is in between the swaths that will print the A's, and so a separate swath is required to print the middle part of the rule. The way the characters and rule are printed is as follows: First, swath 1 is printed which contains all of the upper A and the rule down to location A. Next, swath 2 is printed which contains only the rule from location A (the top of swath 2) to location C...