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# Method of Wide Line Drawing Operation

IP.com Disclosure Number: IPCOM000112468D
Original Publication Date: 1994-May-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 4 page(s) / 74K

IBM

## Related People

Mori, M: AUTHOR [+2]

## Abstract

Disclosed is an method for precise X11 wide line drawing onto the bitmap. UNIX X11 defines a wide line drawing rule which is very preside mathematically.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 53% of the total text.

Method of Wide Line Drawing Operation

Disclosed is an method for precise X11 wide line drawing onto
the bitmap.  UNIX X11 defines a wide line drawing rule which is very
preside mathematically.

A graphic hardware assist should obey this rule and it means
that the hardware should have a sub-pixel addressing mechanism
usually.  This invention realize precise X11 wide line without using
this mechanism.

At first, the outline of the target wide line is drawn with an
new line drawing algorithm.  It is consecutive four times line
drawing and it makes a box.

This box is the outline of the target wide line.  In the
conventional method, a sub-pixel addressing mechanism is necessary
for this operation.

Then the area filling operation fills the box.  This area
filling operation is as same as existing method.

The new line drawing method for the outline of target wide line
is on the Brethenham algorithm.  The difference is the dot on
decision rule.

Usually, the corner coordinate of outline of a wideline is on
sub-pixel address.  This invention converts the sub-pixel information
into integer information at first and performs a line drawing like
the integer Brethemham algorithm.

In Fig. 1, a-b-c-d shows the outline of width 2 line which is
defined by the start point M and the end point N.

Four lines which are ab, bc, cd, ad are drawn by following
method.  Here, line ad is picked up for explanation.

(1) Set start point.  To draw ad as a part of outline of wide
line, the actual start point is K and end point is  L.

These actual start and end points are determined by the certain
rule.  In this case, the start point is the lower right integer point
of line ab and the end point is lower left point of extended line ab.

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