Rendering a text image following a line

• US 8,917,276 B2
• Filed: 03/19/2013
• Issued: 12/23/2014
• Est. Priority Date: 06/30/2011
• Status: Active Grant

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Google Inc. (Alphabet Inc.)
• Inventors: Cornell, Brian
• Primary Examiner(s): Brier, Jeffery A
• Assistant Examiner(s): BUTTRAM, ALAN T
• Application Number:
  US13/847,376
• Publication Number:
  US 20130215120A1
• Time in Patent Office: 644 Days
• Field of Search: 345467-4691, 345471-472, 382177-178
• US Class Current: 345/470
• CPC Class Codes: G06T 11/20 Drawing from basic elements, e.g. lines or circles
• CPC Class Codes: G06T 11/203 Drawing of straight lines or curves

Abstract

A graphics or image rendering system, such as a map image rendering system, receives image data from an image database in the form of vector data that defines various image objects, such as roads, geographical boundaries, etc., and textures defining text strings to be displayed on the image to provide, for example, labels for the image objects. The imaging rendering system renders the images such that the individual characters of the text strings are placed on the image following a multi-segmented or curved line. This rendering system enables text strings to be placed on a map image so that the text follows the center line of a curved or angled road or other image feature without knowing the specifics of the curvature of the line along which the text will be placed when creating the texture that stores the text string information. This feature provides enhanced visual properties within a map image as it allows, for example, road names to be placed anywhere inside a road following the curvature of the road, thus providing a pleasing visual effect within the map image.

Claims

1. An image rendering engine, comprising;

a communications network interface;

a processor;

a memory coupled to the processor;

a display device coupled to the processor;

a first routine, stored in the memory, that executes on the processor to receive, via the communications network interface, a set of vector data comprising data defining one or more image objects and to obtain from the memory one or more text string lookup tables, wherein one of the text string lookup tables stores text characters of at least one text string as a set of pixelated text characters and encoding data defining the center position of each of a plurality of text characters associated with the text string;

a second routine, stored in the memory, that executes on the processor to determine a plurality of line segments associated with a line along which the text string is to be rendered, and a range associated with each line segment;

a third routine, stored in the memory, that executes on the processor to determine a text box for each of the plurality of line segments, each of the text boxes being oriented to draw text in an upright position along an associated line segment; and

a fourth routine, stored in the memory, that executes on the processor to;

select one of the text boxes in which to render a text character of the text string;

select one or more pixels of a next one of the text characters of the text string;

determine if a center of the next one of the text characters, when rendered in the selected one of the text boxes on the image, will be within the range of the line segment associated with the selected one of the text boxes; and

render the pixels of the one of the text characters on the display device using the one of the text boxes if a center of the one of the text characters when rendered in the selected one of the text boxes will be within the range of the line segment associated with the selected one of the text boxes and not render the pixels of the one of the text characters on the display device using the one of the text boxes if a center of the one of the text characters when rendered in the one of the text boxes will not be within the range of the line segment associated with the one of the text boxes.

2. The image rendering engine of claim 1, wherein the third routine comprises a vertex shader.

3. The image rendering engine of claim 1, where the fourth routine selects pixels for each one of the text characters of the text string stored within the image lookup table in turn and, for each selected one of the text characters;

determines if the center of the selected one of the text characters, when rendered in the one of the text boxes, will be within the range of the line segment associated with the one of the text boxes,

renders the selected one of the text characters on the display device using the one of the text boxes if the center of the selected one of the text characters when rendered in the one of the text boxes will be within the range of the line segment associated with the one of the text boxes, and

selects a different one of the plurality of text boxes as the one of the text boxes for use in rendering the selected one of the text characters on the display device if the center of the selected one of the text characters, when rendered in the one of the text boxes, will not be within the range of the line segment associated with the one of the text boxes.

4. The image rendering system of claim 1, wherein the fourth routine determines if the center of the one of the text characters, when rendered in the one of the text boxes, will be within the range of the line segment associated with the one of the text boxes by reading a set of encoding data for the one of the text characters, the encoding data specifying the center of the one of the text characters in at least one direction and using the location of the center of the one of the text characters to determine if the center of the one of the text characters, when rendered in the one of the text boxes, will be within the range of the line segment associated with the one of the text boxes.

5. A map image rendering system, comprising:

a database that stores map-related vector image data, the vector image data comprising data defining one or more image objects and one or more text string lookup tables, wherein one of the text string lookup tables stores text characters associated with at least one text string to be rendered as a set of pixelated text characters and encoding data defining the center position of each of a plurality of text characters associated with the text string; and

a map image rendering device communicatively coupled to the database to use the map-related vector image data and to render a map image using the map-related vector image data, the map image rendering device including;

a processor,

a memory coupled to the processor,

a display device coupled to the processor,

one or more applications stored on the memory which, when executed on the processor;

determine a plurality of line segments associated with a line along which a text string is to be rendered and a range associated with each line segment;

form a text box for each of the plurality of line segments, each of the text boxes being oriented to draw text in an upright position along an associated line segment in the image and having a set of range values defined by the range of the associated line segment; and

for each text character in the text string,

(1) read the encoding data from the text string lookup table;

(2) determine the text box having a range value in which the center position of the text character will fall when the text character is rendered on the image; and

(3) render the text character as part of the image on the display device using the determined one of the text boxes.

6. A map image rendering system of claim 5, wherein the encoding data further defines a width of each of the text characters associated with the text string.

7. A map image rendering system of claim 5, wherein the one or more applications includes one or more image shaders that form a text box for each of the plurality of line segments by forming each of the text boxes oriented along a length of an associated one of the line segments and having a length, in the direction of the length of the associated line segment, larger than the range of the associated line segment.

8. A map image rendering system of claim 7, wherein the one or more image shaders form a text box for each of the plurality of line segments so that the start of each text box extends a predetermined distance, in the direction of the length of the associated line segment, before the start of the line segment and so that the end of the text box extends the predetermined distance, in the direction of the line segment, past the end of the line segment.

9. A map image rendering system of claim 5, wherein one of the text string lookup tables stores the encoding data defining a center position of each of the text characters associated with a text string as a pixel value for each column of pixels of the text string, wherein a particular pixel value is used to define a center position of a text character and other pixel values are incremented or decremented from the particular pixel value to indicate at each pixel column of a text character, a distance to the center position of the text character.

10. A map image rendering system of claim 5, wherein one of the text string lookup tables further stores a set of glyphs within a field of glyphs in the text string lookup table, and stores further encoding data for each text character associated with the text string, the further encoding data referencing one of the glyphs to use as the text character at a position within the text string.

11. A map image rendering system of claim 5, wherein the one or more image shaders determine the text box having a range value in which the center position of the text character will fall when the text character is rendered on the image by;

selecting one of the text boxes in which to render the text character of the text string,

determining if the center position of the text character, when rendered in the selected one of the text boxes, will be within the range of the line segment associated with the selected one of the text boxes, and

rendering the text character in the image on the display device using the selected one of the text boxes if the center position of the text character when rendered in the selected one of the text boxes will be within the range of the line segment associated with the selected one of the text boxes or otherwise selecting a different one of the plurality of text boxes as the selected one of the text boxes if the center position of the text character, when rendered in the selected one of the text boxes, will not be within the range of the line segment associated with the selected one of the text boxes.