Rendering sub-pixel precision characters having widths compatible with pixel precision characters

In a processing device associated with a display device, wherein the display device has a plurality of pixels each having a plurality of pixel subcomponents and wherein each pixel sub-component within a particular pixel has a color that is different from the other pixel sub-components, a method of using a pixel sub-component precision rendering process to display a document that has been created in association with a full pixel precision rendering process, the method comprising the steps of:

• obtaining a document that has been created using a full pixel precision rendering process in which the widths of character features of the character are integer multiples of the width of the pixels, the document including character data that represents a plurality of characters, the characters having first advance widths and the document having an overall formatting and length when displayed using the full pixel precision rendering process;
• adjusting a feature of at least some of the characters with pixel sub-component precision;
• and
• displaying the document on the display device using a pixel sub-component precision rendering process wherein:
• the feature of at least some of the characters is displayed on the display device with a width having a value that is not an integer multiple of the width of the pixels and is different from a width of the selected feature that would be displayed if the selected feature were to be displayed using the full pixel precision rendering process;
• and
• the plurality of characters have second advance widths on the display device that are equal to the first advance widths, such that the document maintains the same overall formatting and length when rendered using the pixel sub-component precision rendering process that the document would have if the document were to be rendered using the full pixel precision rendering process.

A computer program product for implementing, in a processing device associated with a display device, wherein the display device has a plurality of pixels each having a plurality of pixel sub-components, wherein each pixel sub-component of a particular pixel has a color that is different from other pixel sub-components of the particular pixel, a method of displaying a character such that a selected feature of the character has a width rendered with pixel sub-component precision, while maintaining an advance width of the character having a value that is an integer multiple of the width of the pixels, the computer program product comprising:

• a computer-readable medium carrying executable instructions for performing the method, wherein the method includes the steps of:
• obtaining existing image data representing a character having a selected feature, the character having a coarse advance width that is associated with the character when the character is displayed using a full pixel precision rendering process in which the widths of character features of the character are integer multiples of the width of the pixels;
• adjusting a width of the selected feature of the character to pixel sub-component precision;
• and
• based on the image data, displaying the character on the display device using a pixel sub-component precision rendering process wherein:
• the selected feature is rendered with pixel sub-component precision, such that the said adjusted width of the selected feature is different from the width of the selected feature that would be displayed if the selected feature were to be displayed using the full pixel precision rendering process and is not an integer multiple of the width the pixels;
• and
• the displayed advance width of the character has a value that is an integer multiple of the width of the pixels and is equal to the coarse advance width, such that the displayed advance width of the character obtained using the pixel sub-component precision rendering process is the same as the coarse advance width that would be obtained if the character were to be rendered using the full pixel precision rendering process.

A computer system comprising:

• a processing unit;
• a display device including a plurality of pixels, each of the plurality of pixels including a plurality of separately controllable pixel sub-components;
• and
• a computer program product including a computer-readable storage volume carrying executable instructions that, when executed, enable the computer system to implement a method of displaying a character such that a selected feature of the character has a width rendered with pixel sub-component precision, while maintaining an advance width of the character having a value that is an integer multiple of the width of the pixels, the method comprising the steps of:
• obtaining existing image data representing a character having a selected feature, the character having a coarse advance width that is associated with the character when the character is displayed using a full pixel precision rendering process in which the widths of character features of the character are integer multiples of the width of the pixels;
• adjusting a width of the selected feature of the character to pixel sub-component precision;
• and
• based on the image data, displaying the character on the display device using a pixel sub-component precision rendering process wherein:
• the selected feature is rendered with pixel sub-component precision, such that the said adjusted width of the selected feature is different from the width of the selected feature that would be displayed if the selected feature were to be displayed using the full pixel precision rendering process and is not an integer multiple of the width the pixels;
• and
• the displayed advance width of the character has a value that is an integer multiple of the width of the pixels and is equal to the coarse advance width, such that the displayed advance width of the character obtained using the pixel sub-component precision rendering process is the same as the coarse advance width that would be obtained if the character were to be rendered using the full pixel precision rendering process.

In a processing device associated with a display device, wherein the display device has a plurality of pixels each having a plurality of pixel sub-components, a method of displaying a character such that a stem of the character has a width rendered with pixel sub-component precision, while maintaining an advance width of the character having a value that is an integer multiple of the width of the pixels, the method comprising the steps of:

• retrieving image data representing a character having a stem from a storage volume associated with the processing device, the image data identifying key points of the character and a parent/child hierarchy of the key points, the key points including a left side bearing point, a point on a left edge of the stem, and a point on a right edge of the stem, wherein the character has a coarse advance width;
• using the parent/child hierarchy:
• positioning the left side bearing point to a first grid point on a grid defined by the pixels, the first grid point corresponding to a boundary between pixels;
• positioning the point on the left edge to a second grid point on the grid, the second grid point corresponding to a boundary between pixels;
• and
• positioning the point on the right edge to a third grid point on the grid, the third grid point being located at a distance from the second grid point, the distance having pixel sub-component precision;
• and
• based on the image data, displaying the character on the display device using a pixel sub-component precision rendering process wherein the selected feature is rendered with pixel sub-component precision and the displayed advance width of the character has a value that is an integer multiple of the width of the pixels and is equal to the coarse advance width.

In a processing device associated with a display device, wherein the display device has a plurality of pixels each having a plurality of pixel sub-components a method of fitting character data to a grid defined by the pixels in preparation for rendering an image on the display device, the method comprising the acts of:

• obtaining character data representing a character having a stem;
• positioning a selected point located on a first edge of the stem, a left side bearing point of the character, and a right side bearing point of the character at:
• grid points on the grid that correspond to boundaries between pixels on the display device, wherein the left side bearing point is positioned to a first grid point that corresponds to a specified boundary between pixels;
• determining a coarse advance width of the character that would be generated if the character were to be displayed using a full pixel precision rendering process;
• positioning a point on a second edge of the stem on the grid such that a width of the stem has a value having pixel sub-component precision, the second edge being opposite the first edge;
• and
• positioning the right side bearing point to a second grid point such that the left side bearing point and the right side bearing point are separated by a distance equal to the coarse advance width.

In a processing device associated with a display device, wherein the display device has a plurality of pixels each having a plurality of pixel sub-components, a method of using a pixel sub-component precision rendering process to display a document that has been created in association with a full pixel precision rendering process, the method comprising the steps of:

• obtaining a document that has been created using a full pixel precision rendering process, the document including character data that represents a plurality of characters, the characters having first advance widths when displayed using the full pixel precision rendering process;
• positioning a left side bearing point of the character data associated with a particular character to a first point on a grid defined by the pixels of the display device, the first point corresponding to a first boundary between pixels;
• positioning a point on a left edge of a selected feature of the particular character to a second point on the grid, the second point corresponding to a second boundary between pixels;
• positioning a point on a right edge of the selected feature to a third point on the grid, the third point being selected with sub-pixel precision;
• and
• displaying the document on the display device using a pixel sub-component precision rendering process whereby the selected feature of at least some of the characters is displayed on the display device with a width having a value that is not an integer multiple of the width of the pixels, the plurality of characters having second advance widths on the display device that are equal to the first advance widths.