Automatic optimization of the posistion of stems of text characters

• US 20050237342A1
• Filed: 06/24/2005
• Published: 10/27/2005
• Est. Priority Date: 10/07/1998
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Beat Stamm, Claude Betrisey, Gregory C. Hitchcock, Matt Conway
• Inventors: Hitchcock, Gregory C., Stamm, Beat, Betrisey, Claude, Conway, Matt
• Granted Patent: US 7,148,893 B2
• Time in Patent Office: Days
• US Class Current: 345/613
• CPC Class Codes: G06T 11/203 Drawing of straight lines or curves
• CPC Class Codes: G09G 2340/0457 Improvement of perceived resolution by subpixel rendering
• CPC Class Codes: G09G 3/3607 for displaying colours or for displaying grey scales with a specific pixel layout, e.g. using sub-pixels display of colours in flat matrix panels other than liquid crystal displays G09G3/2003; grey scales specific for television H04N3/127
• CPC Class Codes: G09G 5/02 characterised by the way in which colour is displayed details of colour display specific for CRTs G09G1/28; specific for flat matrix panels other than liquid crystal displays G09G3/2003; specific for liquid crystal displays G09G3/3607
• CPC Class Codes: G09G 5/24 Generation of individual character patterns
• CPC Class Codes: G09G 5/28 for enhancement of character form, e.g. smoothing

Abstract

Automatically positioning of typographical features, such as vertical stems or horizontal segments of a character, on high contrast pixel sub-component boundaries as part of a rendering process that uses separately controllable pixel sub-components of pixels to represent different portions of the character. In order to identify the typographical features of the character that are to be aligned with high contrast pixel sub-component boundaries, topology of the character is analyzed at runtime. In display devices having vertical stripes of same-colored pixel sub-components, character legibility is increased when the left edges of stems are aligned with high contrast boundaries between pixel sub-components. Processing time and resources are conserved by performing a partial, rather than a full, topological analysis of the character. For example, some font files include data structures that define the position of key control points associated with the character, thereby indicating where the stems or other typographical features are located, and the relationship between different typographical features.

Claims

1. A system having a display device, the display device having a plurality of pixels each having a plurality of pixel sub-components of different colors, the system further comprising a processor for processing computer-executable instructions stored on one or more computer-readable media of the system and that are configured for implementing a method of adjusting image data to a grid defined by the pixels and pixel sub-components in preparation for rasterizing an image on the display device, the method comprising:

obtaining image data having selected elements with positions relative to the grid, the positions of at least one of the selected elements of the obtained image data not coinciding with a boundary between pixel sub-components;

hinting the image data such that a typographical feature defined by one or more of the selected elements is adjusted to a position on the grid that corresponds to a selected boundary between pixel sub-components, the selected boundary being designated as a high contrast boundary due to the color contrast of the sub-pixel components which define the boundary, and which may comprise a boundary other than one which is between pixels; and

displaying the image on the display device using the image data, the typographical feature being displayed at the high contrast boundary.

2. A system as defined in claim 1, wherein the image data represents a character, the method further comprising analyzing the topology of the character at runtime to identify the typographical feature that is to be adjusted.

3. A system as defined in claim 1, wherein the image is displayed such that individual pixel sub-components of the pixels represent spatially different portions of the image data rather than the different portions being represented by entire pixels that include the individual pixel sub-components.

4. A system as defined in claim 1, wherein the typographical feature is a horizontal segment of a character represented by the image data.

5. A system as defined in claim 1, wherein the typographical feature is a stem of a character represented by the image data.

6. A system as defined in claim 5, wherein hinting the image data is conducted such that a left edge of the stem is aligned with the high contrast boundary.

7. A system as defined in claim 1, wherein hinting the image data comprises:

grid fitting the image data to grid points of the grid that corresponds to the pixels and pixel sub-components of the display device such that the one or more elements defining the typographical feature of the image data correspond to the grid points;

phase adjusting the typographical feature such that the typographical feature coincides with the high contrast boundary; and

interpolating the image data such that the position on the grid of remaining elements of the image data is adjusted.

8. A system as defined in claim 7, wherein phase adjusting further comprises:

analyzing hinting instructions associated with the image data for patterns that are indicative of the typographical feature;

deriving, from the hinting instructions, a directed acyclic graph, wherein the topology of the typographical feature is at least partially defined by one or more nodes of the directed acyclic graph; and

based on a traversal of the directed acyclic graph, identifying the position of the typographical feature and repositioning the typographical feature to the high contrast boundary.

9. A system as defined in claim 8, wherein analyzing the hinting instructions further comprises searching for a selected pattern of distances having specified colors associated with the typographical feature.

10. A system as defined in claim 1, wherein the method further comprises mapping spatially different sets of one or more samples of the image data to individual pixel sub-components of the pixels rather than mapping samples to entire pixels.

11. A system as recited in claim 1, wherein the elements include one or more control points and the image data is associated with a character, wherein hinting the image data comprises:

analyzing the image data associated with the character, the image data defining;

an outline of the character using at least the one or more control points;

distances between key control points; and

a parent/child relationship of the key control points;

identifying distances of the character that are indicative of typographical features of the character to be positioned on high contrast boundaries, the identified distances being associated with at least some of the key control points; and

positioning the identified key control points of the character to grid points on the grid that correspond to high contrast boundaries of pixel sub-components on the display device.

12. A system as defined in claim 11, wherein the distances include black distances which are interior to the outline of the character, white distances that are exterior to the outline of the character and grey distances which are a combination of black and white distances.

13. A system as defined in claim 11, wherein the distances define a stem width identified by the at least some of the key control points.

14. A system as defined in claim 11, wherein the method further comprises positioning the stems of the character.

15. A system as defined in claim 11, wherein the high contrast boundary is between blue pixel sub-components and green pixel sub-components, the blue pixel sub-components being interior to the character and the green pixel sub-components being exterior to the character.

16. A system as defined in claim 11, wherein the high contrast boundary is between red pixel sub-components and green pixel sub-components, the red pixel sub-components being exterior to the character and the green pixel sub-components being interior to the character.

17. A system as defined by claim 1, wherein hinting the image data comprises:

deriving a parent/child hierarchy representative of certain ones of said selected elements from the image data;

examining the image data for patterns that indicate typographical features, wherein the patterns are identified by the certain ones of said selected elements and each node of the hierarchy is associated with one of the typographical features; and

while traversing a data structure representing the hierarchy, phase adjusting one or more selected typographical features by positioning the certain ones of said selected elements associated with the selected typographical features on grid points of the grid that correspond to a high contrast boundary between pixel sub-components, the high contrast boundary not being a boundary between pixels.

18. A system having a display device having a plurality of pixels for displaying image data, each pixel having a plurality of pixel sub-components, the system comprising a processor for processing computer-executable instructions stored on one or more computer-readable media of the system and that are configured for implementing a method for hinting the image data, the method comprising:

grid fitting the image data to grid points of a grid that corresponds to the pixels and pixel sub-components of the display device such that one or more elements defining a typographical feature of the image data correspond to the grid points;

phase adjusting the typographical feature such that the typographical feature coincides with a location of the grid that represents a boundary between pixel sub-components, the boundary being designated as a high contrast boundary, wherein phase adjusting comprises;

analyzing hinting instructions associated with the image data for patterns that are indicative of the typographical feature;

deriving, from the hinting instructions, a directed acyclic graph, wherein the topology of the typographical feature is at least partially defined by one or more nodes of the directed acyclic graph; and

based on a traversal of the directed acyclic graph, identifying the position of the typographical feature and repositioning the typographical feature to the high contrast boundary; and

interpolating the image data such that the position on the grid of remaining elements of the image data is adjusted.

19. A system as recited in claim 18, wherein the method further comprises:

traversing the directed acyclic graph;

encountering a node that corresponds to a point of the image data that is to be repositioned on the grid; and

accounting for an error introduced by a repositioning of a point corresponding to a previous node of the directed acyclic graph.

20. A system as defined in claim 18, wherein analyzing the hinting instructions further comprises searching for a selected pattern of distances having specified colors associated with the typographical feature.