US 5,293,472 AGranted

Method of generating lines and curves of user specified thicknesses on a raster device

AssigneeInternational Business Machines Corporation

InventorJeffrey B. Lotspiech

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Abstract

A method of drawing a straight or curved line of predetermined thickness on a raster device having a display or printed page consisting of a rectangular array of pels. Initially, a spine list is generated which comprises a digitization of a spine that can be swept by a preselected pen of thickness 2t centered on the spine to draw the line or "stroke." The next step is to generate penleft and penright lists representing the X and Y coordinate values of the left and right sides of the pen. Thereafter, left and right lists representing a pair of boundaries of the stroke are generated by starting at a first end of the spine list and sequentially moving toward a second end of the spine list. For each position in the spine list, the X, Y coordinate values thereof are added to the X and Y coordinate values in the penleft list. The left list is updated when any of the resulting sums yield an X value less than the current X value for the corresponding Y value in the left list. The right list is similarly updated for each position in the spine list when any of the resulting sums yield an X value more than the current X value for the corresponding Y value in the right list. Finally, the stroke is drawn by filling in between the left and right lists.

Claims14

Dependent claims

In a graphics processing system including a graphics processor and a raster device, a method of drawing a straight or curved stroke of predetermined thickness on a rectangular array of pels, comprising the steps of:

in the graphics processor:
generating a spine list comprising a digitization of a spine that can be swept by a preselected pen of thickness 2t centered on the spine to draw the stoke, the spine list including a set of X, Y coordinate values of a set of the pels in the array intersected by the spine;
generating a penleft list and a penright list, the penleft list including X, Y coordinate values of the left side of the pen and the penright list including X, Y coordinate values of the right side of the pen, respectively;
and
generating left and right lists representing a pair of boundaries of the stroke by starting at a first end of the spine list and moving toward a second end of the spine list and for each sequential position in the spine list adding the X, Y coordinate values thereof to the X, Y coordinate values in the penleft list and updating the left list when any of the resulting sums yields an X value less than the current X value for the corresponding Y value in the left list and updating the right list when any of the resulting sums yields an X value more than the current X value for the corresponding Y value in the right list;
and
drawing the stroke with the raster device by filling in pel positions between the pair of boundaries represented by the left and right lists.

4 more elements

Dependencies are inferred from the claim text.