Method for compressing and decompressing digital image data

Claim 2

A lossless compression method for a digitized image, the digitized image including a current pixel, which has a value X, and two neighboring pixels adjacent to the current pixel, the two neighboring pixels having values A and B respectively, and Δ being the difference between A and B, comprising the steps: using a first algorithm to generate a predicted value P for the current pixel based on the values A and B; calculating a prediction error e' based on a one-to-one mapping of the difference e between the predicted value P and the current value X; generating a parameter K which is a predetermined non-constant function of the difference Δ; encoding the prediction error e' of the current pixel by assigning a Rice code thereto based on the parameter K, to thereby obtain a Rice encoded code; and replacing the Rice encoded code by a predetermined code pattern followed by the current value X if the Rice encoded code obtained for the current pixel is longer than a predetermined length.

Claim 3

Method according to claim 1, wherein the predetermined code pattern is a set of consecutive "1" bits.

Claim 4

Method according to claim 1, wherein the difference e is a signed quantity and may have a positive value or a negative value; the prediction error e' is an unsigned quantity and does not include any negative values; a small absolute value of the difference e corresponds to a small value of the prediction error e'; and the number of bits required to represent the unsigned prediction error e' is less than the number of bits required to represent the signed difference e.

Claim 5

The method of claim 3, wherein the predetermined function for generating K consists essentially of: k=1 Δ≦2 k=2 2<Δ≦4 k=3 4<Δ≦8 k=4 8<Δ.

Claim 6

Method according to claim 1, further comprising a subsequent decompression procedure comprising the steps of: determining whether the leading bits of the encoded code consists of the predetermined code pattern; and if the leading bits of the encoded code consist of the predetermined code pattern, outputting X.

Claim 7

Method according to claim 1, further comprising a subsequent decompression procedure comprising the steps of: determining whether the leading bits of the encoded code consist of the predetermined code pattern; and if the leading bits of the encoded code does not consist of the predetermined code pattern, generating a decoded predicted value P for the current pixel based on previously decoded values A and B for the neighboring pixels, using said predetermined function to generate a decoded parameter K from the decoded difference Δ of the decoded values A and B; using the decoded value of the parameter K and the inverse of said Rice code to obtain a decoded prediction error e' from the encoded code; using a second mappling function which is the inverse of said one-to-one mapping function to obtain a decoded difference e from the decoded prediction error e'; and adding the decoded predicted value P to the decoded difference e to obtain the decoded value X of the current pixel.

Claim 8

The method of claim 1, wherein the predetermined function for generating K consists essentially of: k=1 Δ≦2 k=2 2<Δ≦4 k=3 4<Δ≦8 k=4 8<Δ.

Claim 9

A lossless compression method for a digitized image, the digitized image including a current pixel, which has a value X, and two neighboring pixels adjacent to the current pixel, the two neighboring pixels having values A and B respectively, and Δ being the difference between A and B, comprising; an encoding process including the steps: using a first algorithm to generate a predicted value P for the current pixel based on the values A and B; calculating a prediction error e' based on a one-to-one mapping of the difference e between the predicted value P and the current value X; generating a parameter K which is a predetermined non-constant function of the difference Δ; encoding the prediction error e' of the current pixel by assigning a Rice code thereto based on the parameter K, to thereby obtain a Rice encoded code; and if the Rice encoded code obtained for the current pixel is longer than a predetermined length, replacing the Rice encoded code by a predetermined code pattern followed by the current value X a subsequent decoding process comprising the steps: determining whether the leading bits of the encoded code consists of the predetermined code pattern: if the leading bits of the encoded code consist of the predetermined code pattern, outputting X, determining whether the leading bits of the encoded code consist of the predetermined code pattern: if the leading bits of the encoded code does not consist of the predetermined code pattern, generating a decoded predicted value P for the current pixel based on previously decoded values A and B for the neighboring pixels, using said predetermined function to generate a decoded parameter K from the decoded difference Δ of the decoded values A and B; using the decoded value of the parameter K and the inverse of said Rice code to obtain a decoded prediction error e' from the encoded code and; using a second mapping function which is the inverse of said one-to-one mapping function to obtain a decoded difference e from the decoded prediction error e'; and adding the decoded predicted value P to the decoded difference e to obtain the decoded value X of the current pixel, wherein the predetermined code pattern is a set of consecutive "1" bits, the difference e is a signed quantity and may have a positive value or a negative value; the prediction error e' is an unsigned quantity and does not include any negative values; a small absolute value of the difference e corresponds to a small value of the prediction error e'; the number of bits required to represent the unsigned prediction error e' is less than the number of bits required to represent the signed difference e; and the predetermined function for generating K consists essentially of: k=1 Δ≦2 k=2 2<Δ≦4 k=3 4<Δ≦8 k=4 8<Δ.

Claim 10

A lossless compression method for a digitized image, the digitized image including a current pixel, which has a value X, and two neighboring pixels adjacent to the current pixel, the two neighboring pixels having values A and B respectively, and Δ being the difference between A and B, comprising; an encoding process including the steps: using a first algorithm to generate a predicted value P for the current pixel based on the values A and B; calculating a prediction error e' based on a one-to-one mapping of the difference e between the predicted value P and the current value X; generating a parameter K which is a predetermined non-constant function of the difference Δ; encoding the prediction error e' of the current pixel by assigning a Rice code thereto based on the parameter K, to thereby obtain a Rice encoded code; and if the Rice encoded code obtained for the current pixel is longer than a predetermined length, replacing the Rice encoded code by a predetermined code pattern followed by the current value X a subsequent decoding process comprising the steps: determining whether the leading bits of the encoded code consists of the predetermined code pattern: if the leading bits of the encoded code consist of the predetermined code pattern, outputting X, determining whether the leading bits of the encoded code consist of the predetermined code pattern: if the leading bits of the encoded code does not consist of the predetermined code pattern, generating a decoded predicted value P for the current pixel based on previously decoded values A and B for the neighboring pixels, using said predetermined function to generate a decoded parameter K from the decoded difference Δ of the decoded values A and B; using the decoded value of the parameter K and the inverse of said Rice code to obtain a decoded prediction error e' from the encoded code and; using a second mapping function which is the inverse of said one-to-one mapping function to obtain a decoded difference e from the decoded prediction error e'; and adding the decoded predicted value P to the decoded difference e to obtain the decoded value X of the current pixel, wherein the predetermined code pattern is a set of consecutive "1" bits, the difference e is a signed quantity and may have a positive value or a negative value; the prediction error e' is an unsigned quantity and does not include any negative values; a small absolute value of the difference e corresponds to a small value of the prediction error e'; the number of bits required to represent the unsigned prediction error e' is less than the number of bits required to represent the signed difference e; and the predetermined function for generating K consists essentially of: k=1 Δ≦2 k=2 2<Δ≦4 k=3 4<Δ≦8 k=4 8<Δ.