Method and apparatus for simplifying the decoding of data

• US 7,716,166 B2
• Filed: 01/07/2007
• Issued: 05/11/2010
• Est. Priority Date: 01/07/2007
• Status: Expired due to Fees

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Gies, Sean, Albert, Eric J., Begeman, Nathaniel
• Primary Examiner(s): Fleurantin; Jean B.
• Assistant Examiner(s): Ly; Anh
• Application Number:
  US11/650,712
• Publication Number:
  US 20080177769A1
• Time in Patent Office: 1,220 Days
• Field of Search: 707/1, 707100-102, 455/566, 715/277, 714/759, 725135-136, 725/147, 709/217, 709/223, 709/225, 709/226, 709/231, 687/697
• US Class Current: 714/746
• CPC Class Codes: H04N 1/41 Bandwidth or redundancy reduction by scanning H04N1/17 ; methods or arrangements for coding, decoding, compressing or decompressing digital video signals H04N19/00

Abstract

The various methods and devices described herein relate to devices which, in at least certain embodiments, may include a method of decoding data or a data stream in a file, which may include checking for a first data portion of a plurality of data portions in the file, the first data portion having a first data value, reading in data from another data portion of the plurality of data portions, decoding or decompressing the data, performing a checksum operation on the decoded data if the first data portion having the first data value is not detected, and skipping a checksum operation on the decoded data if the first data portion having the first data value is detected. In the embodiment, a checksum operation on encoded data may also be skipped. In an embodiment, the first data value may include information or instructions about how a decoder may decode the data and may also include a tag or identifier.

Claims

1. A method of converting data in a file using an apparatus having a processor and a memory, the method comprising:

checking for a first data portion of a plurality of data portions in the file, the first data portion being a critical data chunk in a Portable Network Graphics (PNG) file and having a first data value;

reading in data from a second data portion of the plurality of data portions;

decoding the data in the second data portion of the plurality of data portions;

wherein decoding the data in the second data portion comprises decoding data for an opaque image encoded with a four-channel blue, green, red and alpha format;

skipping a multiplication of a color value with a transparency value if the first data portion having the first data value is detected;

performing a checksum operation using the processor on the decoded data from the second data portion if the first data portion having the first data value is not detected; and

skipping the checksum operation on the decoded data from the second data portion if the first data portion having a first data value is detected.

2. The method of claim 1 wherein reading in data from a second data portion comprises reading in compressed data from an image data chunk.

3. The method of claim 1 wherein skipping the multiplication of the color value with the transparency value comprises skipping a multiplication of a red, green and blue (RGB) value with an alpha value.

4. The method of claim 1 wherein checking for the first data portion having the first data value comprises checking for the first data portion having an identifier that identities the first data portion as a critical chunk that instructs a decoder to inflate data without a header.

5. A machine-readable storage medium storing executable program instructions which when executed cause the machine to perform a method comprising:

checking for a first data portion of a plurality of data portions in the file, the first data portion being a critical data chunk in a Portable Network Graphics (PNG) file and having a first data value;

reading in data from a second data portion of the plurality of data portions;

decoding the data in the second data portion of the plurality of data portions;

wherein decoding the data in the second data portion comprises decoding data for an opaque image encoded with a four-channel blue, green, red and alpha format;

skipping a multiplication of a color value with a transparency value if the first data portion having the first data value is detected;

performing a checksum operation on the decoded data from the second data portion if the first data portion having the first data value is not detected; and

skipping the checksum operation on the decoded data from the second data portion if the first data portion having the first data value is detected.

6. The machine-readable medium of claim 5 wherein checking for the first data portion comprises checking for a critical data chunk in an image file.

7. The machine-readable medium of claim 5 wherein the method further comprises skipping a checksum operation on data that is not decoded if the first data portion having the first data value is detected.

8. The machine-readable medium claim 5 wherein reading in data from a second data portion comprises reading in deflated data from an image data chunk.

9. The machine-readable medium of claim 5 wherein performing the method further comprises skipping a multiplication of a color value with a transparency value if the first data portion having the first data value is detected.

10. The machine-readable medium of claim 9 wherein the second data portion comprises a premultiplied blue, green and red (BGR) value with an alpha value.

11. The machine-readable medium of claim 5 wherein decoding the data in the second data portion comprises inflating data with little-endian format.

12. An apparatus having a processor and a memory, comprising:

means for checking, including the processor, for a first data portion of a plurality of data portions in the file, the first data portion being a critical data chunk in a Portable Network Graphics (PNG) file And having a first data value;

means for reading in data from a second data portion of the plurality of data portions;

means for decoding the data in the second data portion of the plurality of data portions;

wherein decoding the data in the second data portion comprises decoding data for an opaque image encoded with a four-channel blue, green, red and alpha format;

means for skipping a multiplication of a color value with a transparency value if the first data portion having the first data value is detected;

means for performing a checksum operation using the processor on the decoded data from the second data portion if the first data portion having the first data value is not detected; and

means for skipping the checksum operation on the decoded data from the second data portion if the first data portion having a first data value is detected.

13. An apparatus, comprising:

a processor; and

a memory coupled to said processor, said memory having stored thereon instructions which, when executed by a decoder cause the decoder to perform a method, the method comprising;

checking for a first data portion of a plurality of data portions in a file, the first data portion being a critical data chunk in a Portable Network Graphics (PNG) file and having a first data value;

reading in data from a second data portion of the plurality of data portions;

decoding the data in the second data portion of the plurality of data portions;

wherein decoding the data in the second data portion comprises decoding data for an opaque image encoded with a four-channel blue, green, red and alpha format;

skipping multiplication of a color value with a transparency value if the first data portion having the first data value is detected;

performing a checksum operation on the data from the second data portion if the first data portion having the first data value is not detected; and

skipping the checksum operation on the data from the second data portion if the first data portion having a first data value is detected.

14. The apparatus of claim 13 wherein checking for the first data portion comprises checking for a critical data chunk in an image file.

15. The apparatus of claim 14 wherein the memory further comprises instructions for decoding data including an arbitrary ordering of components for a pixel.

16. The apparatus of claim 13 wherein reading in data from a second data portion comprises reading in image data from a portable networks graphics (PNG) file.

17. The apparatus at claim 13 wherein the memory further comprises instructions to decode data for an opaque image encoded with a 4-channel blue, green, red and alpha (BGRA) format.

18. The apparatus of claim 13 wherein checking for a first data portion having a first data value comprises checking for a data portion that indicates to a decoder that each scan line of an image was filtered with a same filter type.

19. The apparatus of claim 13 wherein checking for a first data portion having a first data value comprises checking for a first data portion that indicates to a decoder that each scan line of an image was filtered with a same filter method.