Method of realising a boundary of a rotated object

A method of determining a discrete boundary for an object to be rendered into a raster pixel image having a plurality of scanlines, the method comprising the steps of:

• receiving the object for rendering;
• rotating the object by a predetermined amount;
• decomposing an outline of the rotated object into line segments, wherein each line segment has a start point and an end point;
• shifting line segments that satisfy a predetermined criterion by a distance less than or equal to a value dependent on a difference between the end point and the start point of the line segment and on a precision with which the line segment is represented;
• determining, for each scanline to be rendered, points of intersection between the line segments and the scanline;
• and
• rounding the points of intersection to an adjacent position selected from a finite set of positions on the scanline, the rounded points of intersection delimiting the discrete boundary.

A method of determining a discrete boundary for an object to be rendered into a raster pixel image having a plurality of scanlines, the method comprising the steps of:

• receiving the object for rendering;
• rotating the object by a predetermined amount;
• decomposing an outline of the rotated object into line segments;
• determining, for each scanline to be rendered, points of intersection between the line segments and the scanline;
• identifying points of intersection that lie on integer values along the scanline;
• shifting the identified points of intersection if the identified points of intersection lie on line segments having a negative slope;
• and
• rounding each point of intersection to an adjacent integer position on the scanline, the rounded points of intersection delimiting the discrete boundary.

An apparatus for determining a discrete boundary for an object to be rendered into a raster pixel image having a plurality of scanlines, the apparatus comprising:

• means for receiving the object for rendering;
• means for rotating the object by a predetermined amount that is an integer multiple of 90 degrees;
• means for decomposing an outline of the rotated object into line segments;
• means for determining, for each scanline to be rendered, points of intersection between the line segments and the scanline;
• and
• means for rounding each point of intersection to an adjacent position selected from a finite set of positions on the scanline using a rule chosen according to the amount of rotation, the rounded points of intersection delimiting the discrete boundary.

An apparatus for determining a discrete boundary for an object to be rendered into a raster pixel image having a plurality of scanlines, the apparatus comprising:

• means for receiving the object for rendering;
• means for rotating the object by a predetermined amount;
• means for decomposing an outline of the rotated object into line segments, wherein each line segment has a start point and an end point;
• means for shifting line segments having a negative slope, wherein the line segment is shifted by a distance less than or equal to a value dependent on a difference between the end point and the start point of the line segment and on a precision with which the line segment is represented;
• means for determining, for each scanline to be rendered, points of intersection between the line segments and the scanline;
• and
• means for rounding the points of intersection to an adjacent position selected from a finite set of positions on the scanline, the rounded points of intersection delimiting the discrete boundary.

An apparatus for determining a discrete boundary for an object to be rendered into a raster pixel image having a plurality of scanlines, the apparatus comprising:

• means for receiving the object for rendering;
• means for rotating the object by a predetermined amount;
• means for decomposing an outline of the rotated object into line segments;
• means for determining, for each scanline to be rendered, points of intersection between the line segments and the scanline;
• means for identifying points of intersection that lie on integer values along the scanline;
• means for shifting the identified points of intersection if the identified points of intersection lie on line segments having a negative slope;
• and
• means for rounding each point of intersection to an adjacent integer position on the scanline, the rounded points of intersection delimiting the discrete boundary.

A computer program product comprising machine-readable program code recorded on a machine-readable recording medium, for controlling the operation of a data processing apparatus on which the program code executes to perform a method of determining a discrete boundary for an object to be rendered into a raster pixel image having a plurality of scanlines, the method comprising the steps of:

• receiving the object for rendering;
• rotating the object by a predetermined amount that is an integer multiple of 90 degrees;
• decomposing an outline of the rotated object into line segments;
• determining, for each scanline to be rendered, points of intersection between the line segments and the scanline;
• and
• rounding each point of intersection to an adjacent position selected from a finite set of positions on the scanline using a rule chosen according to the amount of rotation, the rounded points of intersection delimiting the discrete boundary.

A computer program product comprising machine-readable program code recorded on a machine-readable recording medium, for controlling the operation of a data processing apparatus on which the program code executes to perform a method of determining a discrete boundary for an object to be rendered into a raster pixel image having a plurality of scanlines, the method comprising the steps of:

• receiving the object for rendering;
• rotating the object by a predetermined amount;
• decomposing an outline of the rotated object into line segments, wherein each line segment has a start point and an end point;
• shifting line segments that satisfy a predetermined criterion by a distance less than or equal to a value dependent on a difference between the end point and the start point of the line segment and on a precision with which the line segment is represented;
• and
• determining, for each scanline to be rendered, points of intersection between the line segments and the scanline;
• and
• rounding the points of intersection to an adjacent position selected from a finite set of positions on the scanline, the rounded points of intersection delimiting the discrete boundary.

A computer program product comprising machine-readable program code recorded on a machine-readable recording medium, for controlling the operation of a data processing apparatus on which the program code executes to perform a method of determining a discrete boundary for an object to be rendered into a raster pixel image halving a plurality of scanlines, the method comprising the steps of:

• receiving the object for rendering;
• rotating the object by a predetermined amount;
• decomposing an outline of the rotated object into line segments;
• determining, for each scanline to be rendered, points of intersection between the line segments and the scanline;
• identifying points of intersection that lie on integer values along the scanline;
• shifting the identified points of intersection if the identified points of intersection lie on line segments having a negative slope;
• and
• rounding each point of intersection to an adjacent integer position on the scanline, the rounded points of intersection delimiting the discrete boundary.

A system for determining a discrete boundary for an object to be rendered into a raster pixel image having a plurality of scanlines, the system comprising:

• data storage that stores information about the object, the information having a predetermined precision;
• and
• a processor in communication with said data storage and programmed to:
• rotate the object by a predetermined amount that is an integer multiple of 90 degrees;
• decompose an outline of the rotated object into line segments having a start point and an end point and being represented at the predetermined precision;
• shifting line segments that satisfy a predetermined criterion by a distance less than or equal to a value dependent on a difference between the end point and the start point of the line segment and on the predetermined precision;
• and
• determine, for each scanline to be rendered, points of intersection between the line segments and the scanline, wherein the points of intersection are rounded to an adjacent position selected from a finite set of positions on the scanline using a rule chosen according to the amount of rotation, the rounded points of intersection delimiting the discrete boundary.