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Line Drawing Method Using Bit-Blt on a Bit Map Memory

IP.com Disclosure Number: IPCOM000039762D
Original Publication Date: 1987-Aug-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 30K

Publishing Venue

IBM

Related People

Hatori, M: AUTHOR [+2]

Abstract

This article describes a method for drawing a line in which the first portion of the line is drawn by an appropriate algorithm, such as the Bresenham algorithm, and the rest of the line is drawn by the Bit-Blt (Bit Block Transfer); that is, a rectangular block containing the first portion as a diagonal is transferred on a bit map memory along the line to be drawn. Referring to the drawing, it is assumed that a line L is to be drawn from a first endpoint EP1 to a second endpoint EP2 on a bit map memory. First, a starting or leading portion of the line L is drawn by, for example, the Bresenham algorithm [*]. This portion is drawn from the first endpoint EP1 to an intermediate point IP where a quantization error becomes minimum or zero.

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Line Drawing Method Using Bit-Blt on a Bit Map Memory

This article describes a method for drawing a line in which the first portion of the line is drawn by an appropriate algorithm, such as the Bresenham algorithm, and the rest of the line is drawn by the Bit-Blt (Bit Block Transfer); that is, a rectangular block containing the first portion as a diagonal is transferred on a bit map memory along the line to be drawn. Referring to the drawing, it is assumed that a line L is to be drawn from a first endpoint EP1 to a second endpoint EP2 on a bit map memory. First, a starting or leading portion of the line L is drawn by, for example, the Bresenham algorithm [*]. This portion is drawn from the first endpoint EP1 to an intermediate point IP where a quantization error becomes minimum or zero. Then, a rectangular block BL containing the drawn portion as its diagonal is repeatedly transferred or duplicated by the Bit-Blt operation along the line L to be drawn. In the Bit-Blt operation, the contents of the block BL, which is a source, are ORed with the contents of each destination block shown by dotted lines in the drawing, and its result is stored into the destination block. The destination blocks have the same size as the source block BL, and their particular diagonals form a line together with a corresponding diagonal of the source block BL. This line is not actually drawn, but it overlaps with the line L to be drawn. However, special consideration should be given to t...