Enhanced compression of documents
First Claim
1. A method of compressing captured data comprising steps ofselecting a first quantization table, reducing the dynamic range of captured data, forming data of reduced dynamic range, compressing said data of said reduced dynamic range with said first quantization table forming compressed data, and storing or transmitting said compressed data together with a second quantization table representing a dynamic range other than said reduced dynamic range for expansion of said compressed data having a reduced dynamic range, when decoded.
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Accused Products
Abstract
Increased and potentially extreme compression of documents is achieved by reducing/remapping the dynamic range of the document image possibly together with further image analysis and pre-processing and storing the document together with a substituted table of values chosen to restore or enhance the dynamic range of the document image. Increased or extreme compression is provided notwithstanding multiple image tones (e.g. colors or grey scale levels) even at low contrast within a document, such as a personal check. Such increased compression allows document images to be maintained in rapid-access memory for extended periods without increased storage costs.
73 Citations
14 Claims
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1. A method of compressing captured data comprising steps of
selecting a first quantization table, reducing the dynamic range of captured data, forming data of reduced dynamic range, compressing said data of said reduced dynamic range with said first quantization table forming compressed data, and storing or transmitting said compressed data together with a second quantization table representing a dynamic range other than said reduced dynamic range for expansion of said compressed data having a reduced dynamic range, when decoded.
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8. An apparatus for compressing captured data comprising
means for selecting a first quantization table, means for reducing the dynamic range of captured data, forming data of reduced dynamic range, means for compressing said data of said reduced dynamic range with said first quantization table forming compressed data, and means for storing or transmitting said compressed data together with a second quantization table representing a dynamic range other than said reduced dynamic range for expansion of said compressed data having a reduced dynamic range, when decoded.
Specification