NCJ Number
206560
Journal
Law Enforcement Technology Volume: 31 Issue: 7 Dated: July 2004 Pages: 32,34-36,38
Date Published
July 2004
Length
5 pages
Annotation
This article discusses the debate surrounding the practice of compressing digital image files that are to be used as evidence and presents the results of an evaluation of JPEG 200, a new compression routine.
Abstract
Digital images files are large and compressing the files renders it easier to handle multiple digital image files. There are two types of compression models: lossy and lossless. Lossy compression allows more compression capability but sacrifices some digital information to achieve the compression. Within the forensic field there is a debate surrounding whether lossy compression should be used at all with digital image evidence. One side of the debate asserts that any loss of information, which necessarily results with lossy compression, is unacceptable. The other side of the debate argues that it depends on the circumstances and the way the evidence will be used. Following the description of the debate and a review of the major compression tools available, the JPEG 2000 is evaluated. The JPEG 2000 is a new compression routine that has been designed to provide less loss and less distortion per degree of compression than the JPEG. The evaluation method is described and involved the compression of images using both JPEG and JPEG 2000 and comparing the results to the original digital images. Similar results were achieved with each image, clearly indicating JPEG 2000 as superior to JPEG in terms of less loss and less distortion per degree of compression. Compression ratios of 10 or 20 to 1 are feasible with the JPEG 2000. Forensic investigators on both sides of the debate about compression loss should try the JPEG 2000 as it is superior to its predecessor. Figures