Apparatus and method for compressing Huffman encoded data

• US 6,130,630 A
• Filed: 10/27/1998
• Issued: 10/10/2000
• Est. Priority Date: 10/27/1998
• Status: Expired due to Term

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Grohs, Randall E., Bradburn, Brent M.
• Primary Examiner(s): JEAN PIERRE, PEGUY
• Application Number:
  US09/179,925
• Time in Patent Office: 714 Days
• Field of Search: 341/50, 341/51, 341/67, 341/665, 395/115, 395/112
• US Class Current: 341/51
• CPC Class Codes: G06T 9/005 Statistical coding, e.g. Huffman, run length coding
• CPC Class Codes: H03M 7/42 using table look-up for the coding or decoding process, e.g. using read-only memory H03M7/4006 takes precedence

Abstract

Apparatus and method for compressing Huffman encoded data. The compression apparatus includes a string detector and a record generator. The compression apparatus operates to receive the Huffman encoded data and the length of the codewords used to generate the Huffman encoded data. The string detector then operates to detect each set of repeating strings and each non-repeating string in the encoded data. Each set of repeating strings is replaced with a record that indicates the length of the repeating string, the number of repeats and an instantiation of the repeating string. In addition, each non-repeating string is replaced with a record that indicates the length of the non-repeating string and the non-repeating string. The resulting compressed Huffman data can then be transmitted to a printer.

Claims

1. Apparatus for converting Huffman encoded data into a plurality of records comprising

(a) means for detecting a series of identical Huffman code words in the Huffman encoded data;

and

(b) means for replacing the series with a single record, the record including only one of the identical Huffman code words and an indicator indicating the number of Huffman code words present in the series.

2. The apparatus as recited in claim 1, wherein the Huffman encoded data describes a digital image.

3. The apparatus as recited in claim 2, wherein the series is associated with a uniformly colored area in said digital image.

4. The apparatus as recited in claim 3, wherein said uniformly colored area is white.

5. The apparatus as recited in claim 4, further comprising means for transmitting said record to a printer.

6. A method for converting Huffman encoded data, including a series of identical Huffman code words, into a plurality of records, comprising:

(a) analyzing the Huffman encoded data to identify the series; and

(b) replacing the series with a first record, the first record including only a single one of the identical Huffman code words and an indicator indicating the number of Huffman code words present in the series.

7. The method of claim 6, wherein the first record further includes a second indicator indicating the length of the identical Huffman Code word.

8. The method of claim 7, further comprising:

(c) analyzing said Huffman encoded data to identify a non-repeating Huffman code word, and

(d) replacing the non-repeating Huffman code word with a second record, the second record including only a single one of the non-repeating Huffman code word and a third indicator indicating the length of the non-repeating Huffman code word.

9. The method of claim 8, wherein the Huffman encoded data describes a digital image.

10. The method of claim 9, further comprising:

(e) transmitting the first and second record to a printer.