Compression Of Text Contents For Display Remoting

• US 20120294523A1
• Filed: 05/19/2011
• Published: 11/22/2012
• Est. Priority Date: 05/19/2011
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Abdo, Nadim Y., Albu, Voicu Anton
• Granted Patent: US 8,582,886 B2
• Time in Patent Office: Days
• US Class Current: 382/166
• CPC Class Codes: G06V 30/10 Character recognition
• CPC Class Codes: G06V 30/158 using character size, text spacings or pitch estimation

Abstract

Embodiments of the invention compress an image that contains a representation of text. Embodiments take an image of graphical data and determines one or more portions of that image that have a high probability of containing text. Embodiments then take each such portion of the image and determines one or more rows of text within each portion (where text does, in fact, exist within the portion). The embodiments then traverse each vertical band of pixels of each row to determine sub-glyphs. Where a particular sub-glyph is encountered for the first time, the embodiments cache that sub-glyph, and send it (or a compressed representation thereof) to a client in a remote presentation session. Where a particular sub-glyph has been cached already, the embodiments send a reference to that cached vertical band to the client.

Claims

1. A method for compressing an image, comprising:

determining a top and bottom of a row of text within the image based on a number of background pixels in two adjacent horizontal rows of pixels of the image;

determining a first vertical band of pixels of the row of text, the first vertical band of pixels spanning between the top and bottom and comprising a first image portion;

storing the first image portion in a first memory location; and

in response to determining that a second vertical band of pixels of the row of text comprises a second image portion that matches the first image portion, storing a reference to the first image portion.

2. The method of claim 1, further comprising:

while storing the first vertical band of pixels in a cache of a processor to determine the first vertical band of pixels, determining a color of a first pixel of the first image portion;

storing a reference to the color in a table, the reference being expressed in fewer bits than the color is expressed in; and

replacing the color of the first pixel with the reference to the color.

3. The method of claim 1, further comprising:

sending the first image portion and the reference to the first image portion to a client via a remote presentation session, such that, in response to receiving the first image portion and the reference to the first image portion, the client displays a graphical output comprising a representation of the first image portion and the second image portion.

4. The method of claim 3, wherein sending the first image portion and the reference to the first image portion to the client via a remote presentation session comprises:

sending the first image portion and the reference to the first image portion to the client via a remote presentation session in response to determining that the first image portion and the reference to the first image portion together do not exceed a storage threshold.

5. The method of claim 3, further comprising:

compressing the first image portion and the reference to the first image portion before sending the first image portion and the reference to the first image portion to the client.

6. The method of claim 1, wherein the row of text comprises a plurality of image portions, the plurality of image portions comprising the first and second image portions, and further comprising:

determining that a number of matching image portions in the plurality of image portions is below a threshold;

encoding the plurality of image portions, such that the reference to the first image portion is not used; and

sending the encoded plurality of image portions to a client via a remote presentation session, such that, in response to receiving the encoded plurality of image portions, the client displays a graphical output comprising a representation of the plurality of image portions.

7. The method of claim 1, further comprising:

replacing a color value of each pixel of the first image portion with a reference to a color table, the reference being expressed in fewer bits than the color value before storing the first image portion in the first memory location.

8. The method of claim 1, wherein determining the top and bottom of the row of text within the image based on the number of background pixels in two adjacent horizontal rows of pixels of the image comprises:

determining the top and bottom of the row of text based on a distribution of background pixels to foreground pixels in the two adjacent horizontal rows of pixels.

9. The method of claim 1, further comprising:

determining a top and a bottom of a second row of text within the image; and

in response to determining that a third vertical band of pixels of the second row of text comprises a third image portion that matches the first image portion, storing a second reference to the first image portion.

10. The method of claim 1, wherein the row of text has an origin, and further comprising:

traversing the first vertical band of pixels from the origin to the top to determine a topmost foreground pixel;

traversing the first vertical band of pixels from the origin to the bottom to determine a bottommost foreground pixel; and

determining the first image portion as spanning the first vertical band of pixels from the topmost foreground pixel to the bottommost foreground pixel.

11. A system for compressing an image, comprising:

a processor; and

a memory communicatively coupled to the processor when the system is operational, the memory bearing processor-executable instructions that, upon execution by the processor, cause the system to at least;

determine a top and bottom of a row of text within the image based on a number of background pixels in two adjacent horizontal rows of pixels of the image;

determine a first vertical band of pixels of the row of text, the first vertical band of pixels spanning between the top and bottom and comprising a first sub-glyph;

store the first sub-glyph in a first memory location; and

in response to determining that a second vertical band of pixels of the row of text comprises a second sub-glyph that matches the first sub-glyph, store a reference to the first sub-glyph.

12. The system of claim 11, wherein the memory further bears processor-executable instructions that, upon execution by the processor, cause the system to at least:

while storing the first vertical band of pixels in a cache of a processor to determine the first vertical band of pixels, determine a color of a first pixel of the first sub-glyph;

store a reference to the color in a table, the reference being expressed in fewer bits than the color is expressed in; and

replace the color of the first pixel with the reference to the color.

13. The system of claim 11, wherein the memory further bears processor-executable instructions that, upon execution by the processor, cause the system to at least:

send the first sub-glyph and the reference to the first sub-glyph to a client via a remote presentation session, such that, in response to receiving the first sub-glyph and the reference to the first sub-glyph, the client displays a graphical output comprising a representation of the first sub-glyph and the second sub-glyph.

14. The system of claim 13, wherein the processor-executable instructions that, upon execution by the processor, cause the system to at least send the sub-glyph and the reference to the first sub-glyph to the client via a remote presentation session further cause the system to at least:

send the first sub-glyph and the reference to the first sub-glyph to the client via a remote presentation session in response to determining that the first sub-glyph and the reference to the first sub-glyph together do not exceed a storage threshold.

15. The system of claim 13, wherein the memory further bears processor-executable instructions that, upon execution by the processor, cause the system to at least:

compress the first sub-glyph and the reference to the first sub-glyph before sending the first sub-glyph and the reference to the first sub-glyph to the client.

16. The system of claim 11, wherein the row of text comprises a plurality of sub-glyphs, the plurality of sub-glyphs comprising the first and second sub-glyphs, and wherein the memory further bears processor-executable instructions that, upon execution by the processor, cause the system to at least:

determine that a number of matching sub-glyphs in the plurality of sub-glyphs is below a threshold;

encode the plurality of sub-glyphs, such that the reference to the first sub-glyph is not used; and

send the encoded plurality of sub-glyphs to a client via a remote presentation session, such that, in response to receiving the encoded plurality of sub-glyphs, the client displays a graphical output comprising a representation of the plurality of sub-glyphs.

17. The system of claim 11, wherein the memory further bears processor-executable instructions that, upon execution by the processor, cause the system to at least:

replace a color value of each pixel of the first sub-glyph with a reference to a color table, the reference being expressed in fewer bits than the color value before storing the first sub-glyph in the first memory location.

18. The system of claim 11, wherein the processor-executable instructions that, upon execution by the processor, cause the system to at least determine the top and bottom of the row of text within the image based on the number of background pixels in two adjacent horizontal rows of pixels of the image further cause the system to at least:

determine the top and bottom of the row of text based on a distribution of background pixels to foreground pixels in the two adjacent horizontal rows of pixels.

19. The system of claim 11, wherein the memory further bears processor-executable instructions that, upon execution by the processor, cause the system to at least:

determine a top and a bottom of a second row of text within the image; and

in response to determining that a third vertical band of pixels of the second row of text comprises a third sub-glyph that matches the first sub-glyph, store a second reference to the first sub-glyph.

20. A computer-readable storage medium for compressing an image, bearing computer-readable instructions that, when executed upon a computer, cause the computer to perform operations comprising:

determining a top and bottom of a row of text within the image based on a number of background pixels in two adjacent horizontal rows of pixels of the image;

determining a first vertical band of pixels of the row of text, the first vertical band of pixels spanning between the top and bottom and comprising a first sub-glyph;

storing the first sub-glyph in a first memory location; and

in response to determining that a second vertical band of pixels of the row of text comprises a second sub-glyph that matches the first sub-glyph, storing a reference to the first sub-glyph.