Adjusted Stroke Rendering

• US 20070176935A1
• Filed: 04/09/2007
• Published: 08/02/2007
• Est. Priority Date: 03/31/2004
• Status: Active Grant

• Current Assignee: Adobe Inc.
• Original Assignee: Adobe Systems Incorporated (Adobe Inc.)
• Inventors: Arnold, R., Dowling, Terence
• Granted Patent: US 7,408,555 B2
• Time in Patent Office: Days
• US Class Current: 345/467
• CPC Class Codes: G06T 11/203 Drawing of straight lines or curves
• 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

Methods and apparatus implementing and using techniques for rendering a stroke (e.g., a line or glyph). An initial adjustment value can be calculated for the stroke, and an offset amount calculated based on the initial adjustment value, such that a minimum number of device pixels will be marked by the stroke after adjusting density values of device pixels representing the stroke. A high resolution representation of the stroke (e.g., a set of device pixels each having an initial density value) is rendered so that one or more edges of the stroke is offset from a device resolution grid by the offset amount. A length of an edge of the stroke that passes through a device pixel can be calculated, and the density value of the device pixel adjusted by a final adjustment value based on the initial adjustment value and the length of the edge of the stroke.

Claims

1. A method of asymmetrically adjusting a rendering of a glyph, comprising:

receiving a glyph associated with a font, the glyph to be rendered at a size and having one or more strokes, each stroke having a first edge and a second edge;

calculating a scaled stem width for rendering the glyph at the size;

calculating a first initial adjustment value for the first edge of each stroke and a second initial adjustment value for the second edge of each stroke;

calculating an offset amount based, being an amount by which one or more strokes of the glyph will be offset from a device resolution grid when a high resolution representation of the glyph is rendered as compared to an original position of an outline of the glyph, such that a minimum number of device pixels will be marked by the one or more strokes after adjusting the density values of one or more device pixels representing the glyph;

rendering the high resolution representation of the glyph so that one or more edges of at least one stroke is offset from the device resolution grid by the offset amount, the high resolution representation representing a set of device pixels and determining an initial density value for each of said device pixels;

for one or more of the device pixels in the set of device pixels, calculating a length of an edge of a stroke that passes through the device pixel;

for each of the one or more device pixels, calculating a final adjustment value based on the length of an edge of a stroke passing through the device pixel and either the first or the second initial adjustment value depending on whether the edge is the first or the second edge of the corresponding stroke; and

adjusting the density values of the one or more device pixels by the corresponding final adjustment value.

2. The method of claim 1, wherein:

calculating the first initial adjustment value comprises;

determining a first initial density value of device pixels along the first edge; and

determining the first initial adjustment value based on the scaled stem width and the first initial density value; and

calculating the second initial adjustment value comprises;

determining a second initial density value of device pixels along the second edge; and

calculating the second initial adjustment value based on the scaled stem width and the second initial density value.

3. The method of claim 1, wherein calculating a length of an edge of a stroke that passes through a device pixel comprises:

identifying initial adjustment pixels along the edges of the high resolution bitmap representation of the glyph, the initial adjustment pixels being high resolution pixels representative of either the first or the second initial adjustment value depending on whether the edge corresponds to the first edge or the second edge;

wherein the length of the edge of a stroke that passes through a device pixel is a ratio of the number of initial adjustment pixels in a direction to a grid ratio in said direction.

4. The method of claim 1, further comprising:

determining a second offset amount, wherein the rendering step comprises rendering the glyph so that edges of the one or more strokes are offset from the device resolution grid in a first direction by the offset amount and offset from the device resolution grid in a second direction by the second offset amount.

5. The method of claim 1, where calculating the offset amount comprises determining the ratio n of the high resolution grid to the device resolution grid and calculating the offset amount as 1/n.

6. The method of claim 1, where calculating the final adjustment value comprises multiplying the first or the second initial adjustment value by the length of the edge of the stroke passing through the device pixel.

7. A computer program product, tangibly stored on a computer-readable medium, for asymmetrically adjusting a rendering of a glyph, comprising instructions operable to cause a programmable processor to:

receive a glyph associated with a font, the glyph to be rendered at a size and having one or more strokes, each stroke having a first edge and a second edge;

calculate a scaled stem width for rendering the glyph at the size;

calculate a first initial adjustment value for the first edge of each stroke and a second initial adjustment value for the second edge of each stroke;

calculate an offset amount based, being an amount by which one or more strokes of the glyph will be offset from a device resolution grid when a high resolution representation of the glyph is rendered as compared to an original position of an outline of the glyph, such that a minimum number of device pixels will be marked by the one or more strokes after adjusting the density values of one or more device pixels representing the glyph;

render the high resolution representation of the glyph so that one or more edges of at least one stroke is offset from the device resolution grid by the offset amount, the high resolution representation representing a set of device pixels and determining an initial density value for each of said device pixels;

for one or more of the device pixels in the set of device pixels, calculate a length of an edge of a stroke that passes through the device pixel;

for each of the one or more device pixels, calculate a final adjustment value based on the length of an edge of a stroke passing through the device pixel and either the first or the second initial adjustment value depending on whether the edge is the first or the second edge of the corresponding stroke; and

adjust the density values of the one or more device pixels by the corresponding final adjustment value.

8. The computer program product of claim 7, wherein:

instructions operable to cause a programmable processor to calculate the first initial adjustment value comprise instructions operable to cause a programmable processor to;

determine a first initial density value of device pixels along the first edge; and

determine the first initial adjustment value based on the scaled stem width and the first initial density value; and

instructions operable to cause a programmable processor to calculate the second initial adjustment value comprise instructions operable to cause a programmable processor to;

determine a second initial density value of device pixels along the second edge; and

calculate the second initial adjustment value based on the scaled stem width and the second initial density value.

9. The computer program product of claim 7, wherein instructions operable to cause a programmable processor to calculate a length of an edge of a stroke that passes through a device pixel comprise instructions operable to cause a programmable processor to:

identify initial adjustment pixels along the edges of the high resolution bitmap representation of the glyph, the initial adjustment pixels being high resolution pixels representative of either the first or the second initial adjustment value depending on whether the edge corresponds to the first edge or the second edge;

wherein the length of the edge of a stroke that passes through a device pixel is a ratio of the number of initial adjustment pixels in a direction to a grid ratio in said direction.

10. The computer program product of claim 7, further comprising instructions operable to cause a programmable processor to:

determine a second offset amount, wherein the instructions operable to cause a programmable processor to render the high resolution representation of the glyph comprise instructions operable to render the glyph so that edges of the one or more strokes are offset from the device resolution grid in a first direction by the offset amount and offset from the device resolution grid in a second direction by the second offset amount.

11. The computer program product of claim 7, where instructions operable to cause a programmable processor to calculate the offset amount comprise instructions operable to cause a programmable processor to determine the ratio n of the high resolution grid to the device resolution grid and calculate the offset amount as 1/n.

12. The computer program product of claim 7, where instructions operable to cause a programmable processor to calculate the final adjustment value comprise instructions operable to cause a programmable processor to multiply the first or the second initial adjustment value by the length of the edge of the stroke passing through the device pixel.

13. A system for asymmetrically adjusting a rendering of a glyph, comprising:

means for receiving a glyph associated with a font, the glyph to be rendered at a size and having one or more strokes, each stroke having a first edge and a second edge;

means for calculating a scaled stem width for rendering the glyph at the size;

means for calculating a first initial adjustment value for the first edge of each stroke and a second initial adjustment value for the second edge of each stroke;

means for calculating an offset amount based, being an amount by which one or more strokes of the glyph will be offset from a device resolution grid when a high resolution representation of the glyph is rendered as compared to an original position of an outline of the glyph, such that a minimum number of device pixels will be marked by the one or more strokes after adjusting the density values of one or more device pixels representing the glyph;

means for rendering the high resolution representation of the glyph so that one or more edges of at least one stroke is offset from the device resolution grid by the offset amount, the high resolution representation representing a set of device pixels and determining an initial density value for each of said device pixels;

for one or more of the device pixels in the set of device pixels, means for calculating a length of an edge of a stroke that passes through the device pixel;

for each of the one or more device pixels, means for calculating a final adjustment value based on the length of an edge of a stroke passing through the device pixel and either the first or the second initial adjustment value depending on whether the edge is the first or the second edge of the corresponding stroke; and

means for adjusting the density values of the one or more device pixels by the corresponding final adjustment value.

14. The system of claim 13, wherein:

means for calculating the first initial adjustment value comprise means for;

determining a first initial density value of device pixels along the first edge; and

determining the first initial adjustment value based on the scaled stem width and the first initial density value; and

means for calculating the second initial adjustment value comprise means for;

determining a second initial density value of device pixels along the second edge; and

calculating the second initial adjustment value based on the scaled stem width and the second initial density value.

15. The system of claim 13, wherein means for calculating a length of an edge of a stroke that passes through a device pixel comprise means for:

identifying initial adjustment pixels along the edges of the high resolution bitmap representation of the glyph, the initial adjustment pixels being high resolution pixels representative of either the first or the second initial adjustment value depending on whether the edge corresponds to the first edge or the second edge;

wherein the length of the edge of a stroke that passes through a device pixel is a ratio of the number of initial adjustment pixels in a direction to a grid ratio in said direction.

16. The system of claim 13, further comprising:

means for determining a second offset amount, wherein means for rendering the high resolution representation of the glyph comprise means for rendering the glyph so that edges of the one or more strokes are offset from the device resolution grid in a first direction by the offset amount and offset from the device resolution grid in a second direction by the second offset amount.

17. The system of claim 13, where means for calculating the offset amount comprise means for determining the ratio n of the high resolution grid to the device resolution grid and calculating the offset amount as 1/n.

18. The system of claim 13, where calculating the final adjustment value comprises multiplying the first or the second initial adjustment value by the length of the edge of the stroke passing through the device pixel.