Browse Prior Art Database

Full Page Overlay Technique for Half Indexing and Overstrike

IP.com Disclosure Number: IPCOM000039804D
Original Publication Date: 1987-Aug-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Finlay, DE: AUTHOR [+6]

Abstract

This article describes a half-indexing and overstrike feature of a baseline character generator that achieves functions such as equation writing. The baseline character generator generates a raster image of a page from a memory that contains a coded and ordered representation of the page. The design enables the printing of two independent pages by electronically overlaying them. Shifting one page a half line offset from the other page is one method of obtaining the half-indexing function. The hardware formats each page alternating one scan or one pair of scans at a time. The scans are alternately fetched, and 'ORed' in the scan buffer-printer interface to get the electronic page overlay.

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Full Page Overlay Technique for Half Indexing and Overstrike

This article describes a half-indexing and overstrike feature of a baseline character generator that achieves functions such as equation writing. The baseline character generator generates a raster image of a page from a memory that contains a coded and ordered representation of the page. The design enables the printing of two independent pages by electronically overlaying them. Shifting one page a half line offset from the other page is one method of obtaining the half-indexing function. The hardware formats each page alternating one scan or one pair of scans at a time. The scans are alternately fetched, and 'ORed' in the scan buffer-printer interface to get the electronic page overlay. Since the character generator, described here, is used on a laser printer without a full page pel buffer, the page is rasterized on the fly and overlaying two simultaneously rasterized pages is the method chosen. Another method of achieving overlay is to make multiple rasterizing passes electronically for each scan line, and overlay them serially instead of simultaneously. This is the method that all- points-addressable (APA) character generators use. The novelty of this baseline character generator feature is the idea of overlaying two pages in parallel and the implementation of this idea into hardware. Hardware to implement this system is shown on pages 1085 - 1099.

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