Adaptive wavelet coding of hyperspectral imagery

• US 6,539,122 B1
• Filed: 03/30/1998
• Issued: 03/25/2003
• Est. Priority Date: 04/04/1997
• Status: Expired due to Term

• Current Assignee: General Dynamics C4 Systems Incorporated (General Dynamics Corporation)
• Original Assignee: General Dynamics Decision Systems, Inc. (General Dynamics Corporation)
• Inventors: Abousleman, Glen Patrick
• Primary Examiner(s): Patel, Jayanti K.
• Assistant Examiner(s): DESIRE, GREGORY M
• Application Number:
  US09/050,293
• Time in Patent Office: 1,821 Days
• Field of Search: 375/240-3-2, 375/241, 375/242, 375/262, 375/265, 348/21, 348/155, 348/192-193, 348/470, 348/607, 358/426, 358/429, 358/455, 370/207, 370/529, 370/535, 382/232, 382/235, 382/253, 382/248, 382/250, 382/251
• US Class Current: 382/240
• CPC Class Codes: G06T 9/007 Transform coding, e.g. discrete cosine transform

Abstract

A hyperspectral image encoder (10) for compressing hyperspectral imagery includes a differential pulse code modulation (DPCM) loop (26) to perform data decorrelation in the spectral domain and a discrete wavelet transform (DWT) processing means (28) to perform decorrelation in the spatial domain. The DPCM loop (26) determines an error image between a present image at the input of the encoder (10) and a predicted image. The DWT processing means (28) then divides the error image into a plurality of frequency subbands and quantizes information within the subbands in accordance with a plurality of predetermined quantization states to provide a coded output signal. In one embodiment, an interband predictor (24) is provided to predict an image, for use in calculating the error image, using the coded output signal.

Claims

1. An apparatus for use in compressing hyperspectral imagery, said hyperspectral imagery including a sequence of images, said apparatus comprising:

a differential pulse code modulation (DPCM) loop for processing at least two images to create an error image;

a discrete wavelet transform (DWT) decomposition unit for decomposing said error image into a plurality of frequency subbands; and

a trellis coded quantization (TCQ) encoder for quantizing information within said plurality of frequency subbands according to a plurality of discrete quantization levels to create a coded output signal;

wherein

said TCQ encoder includes a classification unit for classifying at least one block within each of said plurality of frequency subbands into one of a plurality of classes;

said plurality of frequency subbands includes a first frequency subband that includes a plurality of blocks;

said classification unit includes means for determining a first number of blocks in said first frequency subband that fall within a first class in said plurality of classes and a second number of blocks in said first frequency subband that fall within a second class in said plurality of classes;

said classification unit includes means for adjusting said first number of blocks and said second number of blocks;

said means for adjusting includes means for adjusting using a statistical criterion; and

said statistical criterion includes a combination of a variance value for blocks that fall within said first class and a variance value for blocks that fall within said second class.

2. An apparatus for use in compressing hyperspectral imagery, said hyperspectral imagery including a sequence of images, said apparatus comprising:

a differential pulse code modulation (DPCM) loop for processing at least two images to create an error image;

a discrete wavelet transform (DWT) decomposition unit for decomposing said error image into a plurality of frequency subbands; and

a trellis coded quantization (TCQ) encoder for quantizing information within said plurality of frequency subbands according to a plurality of discrete quantization levels to create a coded output signal;

wherein

said TCQ encoder includes a classification unit for classifying at least one block within each of said plurality of frequency subbands into one of a plurality of classes;

said plurality of frequency subbands includes a first frequency subband that includes a plurality of blocks;

said classification unit includes means for determining a first number of blocks in said first frequency subband that fall within a first class in said plurality of classes and a second number of blocks in said first frequency subband that fall within a second class in said plurality of classes;

said classification unit includes means for adjusting said first number of blocks and said second number of blocks;

said means for adjusting includes means for adjusting using a statistical criterion; and

said statistical criterion includes (σ

₁²)^p1(σ

₂²)^p1, where σ

₁² is a variance for blocks in said first class, σ

₂² is the variance for blocks in said second class, and p₁ is a probability that a block in said first frequency subband belongs to said first class.