Microsoft Technology Licensing, LLC

Microsoft Corporation

Beat Stamm

Gregory Carl Hitchcock

Michael J Duggan

Claude Betrisey

Matt Conway

Paul M Linnerud

John Carlton Platt

Geraldine G Wade

David C Brown

William Hill

Greg C Hitchcock

Gregory Hitchcock

Gregory C Hitchcock

Gregory C Hitchock

The principles of the present invention relate to rendering stroke pairs. A graphical object includes at least a first stroke and a second similarly oriented second stroke collectively representing a stroke pair. A calculated distance between the first stroke and the second stroke is constrained (e.g., to a center line between the strokes) to mitigate the possibility of rounding errors causing the represented stroke pair to be inappropriately rendered. After the stroke pair is constrained, controls points of the individual strokes can be adjusted so that the individual strokes are appropriately rendered at their respective constrained locations. The adjusted stroke pair is constrained between external reference points for appropriate rendering relative to other graphical objects. The graphical object, including the adjusted constrained stroke pair, is rendered at an output device.

Rendering stroke pairs for graphical objects

Methods, systems, and computer program products for adding hinting instructions to a character in order to improve a character bitmap produced from an outline of the character at a certain size and output resolution when the character outline is scan converted. A character is retrieved to be output. A determination is made that the character belongs to a semantic character classifications, and hinting instructions that are associated with the semantic character classification are accessed. The hinting instructions preserve semantic meaning for the character while altering either stroke presence, stroke location, or both for at least one stroke of at least one feature of the character based on a reference character size and output resolution. If the actual character size and output resolution for the character is within a reference character size and output resolution for the hinting instructions, the hinting instructions are executed.

Simplifying complex characters to maintain legibility

Stroke contrast is preserved for a range of font sizes and display resolutions using programmatic constraints or 'hints'. One implementation of a 'font hinting' approach enforces a regularization of stroke weights such that stroke contrast is preserved for font sizes and display resolutions sufficient to render it. Font hinting instructions determine a stroke contrast threshold, which may be used to decide whether to preserve or omit stroke contrast when rendering the glyph. In one implementation, the stroke contrast threshold is based on one or more stroke contrast relationships associated with the typeface. In other implementations, the stroke contrast threshold is based on a minimum size threshold or lowercase/uppercase stroke contrast relationships.

Stroke contrast in font hinting

An auto hinting module defines typographically relevant control points and relative offset constraints for use in composite character generation. Control points in one or more dimensions are defined for each glyph component. The control points may be represented as control points on the outline of the component glyphs, although control points may also be represented by control points positioned relative to the outlines, control lines (e.g., vertical, horizontal, diagonal, etc.) that intersect the outlines, etc. A composite character font hinting module enforces offset constraints between the control points, effectively positioning one of the glyph components relative to the other.

Composite characters font hinting

The principles of the present invention relate to iteratively solving constraints in a font-hinting language. A computing system accesses a more complex constraint that can not be natively expressed based on the vocabulary of the font-hinting language, the more complex constraint constraining at least a portion of the outline. The computing system decomposes the more complex constraint into a plurality of simpler constraints that can be natively expressed based on the vocabulary of the font-hinting language. The computer system represents each of the simpler constraints in corresponding font-hinting language instructions that can be iteratively processed to at least approximate a solution to the more complex constraint. The font-hinting language instructions are iteratively processed at the computing system or another computing system to cause a graphical object to comply, within a specific tolerance, with the more complex constraint.

Iteratively solving constraints in a font-hinting language

The principles of the present invention relate to appropriately rendering a graphical object when a corresponding outline has excessive control points. A computer system identifies a point of junction between a first and second feature of the outline. The computer system accesses an excess control point included in the first or second feature of the outline. The computer system moves the excess control point in a first direction until the position of the excess control point in the first direction is essentially the same as the position of the point of junction in the first direction. The computer system moves the excess control point in a second direction until the position of the excess control point in the second direction is essentially the same as the position of the point of junction in the second direction, the second direction being different from the first direction.

Appropriately rendering a graphical object when a corresponding outline has excessive control points

The principles of the present invention relate to dynamically determining directions of freedom for control points used to represent graphical objects such as text. A computing system identifies a first function that represents a first constraint, solutions to the first function indicating compliance with the first constraint. The computing system calculates, based on the location of a control point and the identified first function, that the control point does not comply with the first constraint. The computing system automatically determines a first direction of freedom in which the control point can be moved to comply with the first constraint such that movement of the control point in the first direction of freedom has a reduced likelihood of causing non-compliance with other constraints.

Dynamically determining directions of freedom for control points used to represent graphical objects

Mechanisms for rendering an object on a portion of a display that includes pixel sub-components for each pixel. The pixel sub-components are striped along a certain direction (e.g., vertically or horizontally). The computing system determines that the object has spatial frequency dominance a direction which happens to be parallel to the striping direction. The computing system then performs sub-component based sampling assuming that the striping direction is perpendicular to the actual striping direction. Then the object is rendered on the display. This may be performed for each object to be displayed. Counterintuitively, this improves the resolution of the character being displayed as compared to performing pixel sub-component based sampling assuming that the striping direction is the same as the actual striping direction.

Sub-component based rendering of objects having spatial frequency dominance parallel to the striping direction of the display

The principles of the present invention relate to appropriately rendering a graphical object when a corresponding outline lacks necessary control points. A computer system calculates the target width for a feature of the graphical object. The computer system calculates the position of a center line corresponding to the feature. The computer system rounds the calculated position of the center line to a grid position based on the calculated target width for the feature. The computer system adjusts the position of one or more control points of the feature to comply with the grid position of the center line.

Appropriately rendering a graphical object when a corresponding outline lacks control points

The principles of the present invention relate to appropriately rendering a graphical object when a corresponding outline has exact or inexact control points. Based on the positions of control points on an outline it is calculated, that between a first parent control point and a second parent control point, the outline passes approximately though the center of a grid location. The positions of the first and second parent control points are adjusted by a first and second fraction of the size of a grid location respectively. The position of the child control point is realigned along a second axis of the grid space based on the positions of the first and second parent control points. The child control point position is rounded by a fraction of the size of a grid location based on the positions of the first and second parent control points.

Appropriately rendering a graphical object when a corresponding outline has exact or inexact control points

The principles of the present invention relate to adaptively filtering outlines of typographic characters to simply representative control data. A filtering module receives a set of control points (and instructions for connecting the control points) representing a graphical object, such as, for example, a typographical character. The filtering module adaptively filters out some variations in the outline of the graphical object to reveal common edges of the outline. The filtering module generates simplified control data that represents an outline of the common edges (e.g., representing a block 'T'). Accordingly, based on the simplified control data, a computing system may be able to more efficiently recognize the graphical object represented by the control points.

Adaptively filtering outlines of typographic characters to simplify representative control data

Methods and systems for selecting different anti-aliasing filters to be applied to objects of image data rendered with pixel sub-component precision based on the attributes of the objects of the graphics image. For example, when rendering a character traditional anti-aliasing applied in the direction parallel to the striping of the pixel sub-components is adapted to the unique requirements of different character font sizes such that a large amount of anti-aliasing is applied to large font sizes while a small amount of anti-aliasing is provided for characters at small font sizes. Displaced sampling is utilized to determine the alpha values for a plurality of vertical samples for each RGB pixel sub-component. The selected anti-aliasing filter is applied to the alpha values to determine the luminous intensity values of the RGB pixel sub-components.

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Redmond, WA, United States of America

Beat Stamm