1、Designation:E282512Standard Guide forForensic Digital Image Processing1This standard is issued under the fixed designation E2825;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indica
2、tes the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This guide provides digital image processing guidelinesto ensure the production of quality forensic imagery for use asevidence in a court of law.1.2 This guide briefly
3、 describes advantages,disadvantages,and potential limitations of each major process.2.Referenced Documents2.1 ISO/IEC Standard:2ISO/IEC 10918-1:1994 Information technologyDigitalcompression and coding of continuous-tone still images:Requirements and guidelines(JPEG)(also published asCCITT Recommenda
4、tion T.81(1992)2.2 SWGIT Material:3SWGDE/SWGIT Glossary SWGDE and SWGIT Digital&Multimedia Evidence Glossary,updated June 8,20123.Terminology3.1 Definitions:3.1.1 artifact,nvisual/aural aberration in an image,video,or audio recording resulting from a technical or operationallimitation.SWGDE/SWGIT Gl
5、ossary3.1.1.1 DiscussionExamples include speckles in ascanned picture or“blocking”in images compressed using theJPEG standard.3.1.2 compression,nprocess of reducing the size of a datafile(see lossy compression and lossless compression).SWGDE/SWGIT Glossary3.1.3 grayscale image,ncontinuous tone image
6、 that hasonly one component.ISO/IEC 10918-1:19943.1.4 grayscale transformation,noperation that modifiesa single channel or component of image data(for example,asingle color).3.1.5 image,nimitation or representation of a person orthing,drawn,painted,photographed,and so forth.SWGDE/SWGIT Glossary3.1.6
7、 image enhancement,nany process intended to im-prove the visual appearance of an image or specific featureswithin an image.SWGDE/SWGIT Glossary3.1.7 lossless,advdescriptive term for encoding and de-coding processes and procedures in which the output of thedecoding procedure(s)is identical to the inp
8、ut to the encodingprocedure(s).ISO/IEC 10918-1:19943.1.8 lossless coding,nmode of operation that refers toany one of the coding processes defined in this guide in whichall of the procedures are lossless.ISO/IEC 10918-1:19943.1.9 lossless compression,ncompression in which nodata are lost and all data
9、 can be retrieved in their original form.SWGDE/SWGIT Glossary3.1.10 lossy,advdescriptive term for encoding and decod-ing processes that are not lossless.ISO/IEC 10918-1:19943.1.11 lossy compression,ncompression in which data arelost and cannot be retrieved in their original form.SWGDE/SWGIT Glossary
10、3.1.12 noise,nvariations or disturbances in brightness orcolor information in an image that do not arise from the scene.SWGDE/SWGIT Glossary3.1.12.1 DiscussionSources of noise include film grain,electronic variations in the input device sensor and circuitry,and stray electromagnetic fields in the si
11、gnal pathway.Itfrequently refers to visible artifacts in an image.3.1.13 original image,naccurate and complete replica ofthe primary image,irrespective of media.SWGDE/SWGIT Glossary3.1.13.1 DiscussionFor film and analog video,the pri-mary image is the original image.3.1.14 primary image,nfirst insta
12、nce in which an image isrecorded onto any media that is a separate,identifiable object.SWGDE/SWGIT Glossary3.1.14.1 DiscussionExamples include a digital image re-corded on a flash card or a digital image downloaded from theinternet.1This guide is under the jurisdiction of ASTM Committee E30 on Foren
13、sicSciences and is the direct responsibility of Subcommittee E30.12 on Digital andMultimedia Evidence.Current edition approved May 1,2012.Published October 2012.DOI:10.1520/E2825-12.2Available from American National Standards Institute(ANSI),25 W.43rd St.,4th Floor,New York,NY 10036,http:/www.ansi.o
14、rg.3Available from Scientific Working Group on Imaging Technology(SWGIT),http:/www.swgit.org.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 3.1.15 restoration,nany process applied to an image thathas been degraded by a known cause(for ex
15、ample,defocus ormotion blur)to remove partially or totally the effects of thatdegradation.SWGDE/SWGIT Glossary4.Summary of Practice4.1 The original image shall be preserved.Any imageprocessing should be applied only to a working copy of theimage.4.2 Any changes made through image processing shall me
16、etthe following criteria:4.2.1 Processing steps are documented in a manner suffi-cient to permit a comparably trained person to understand thesteps taken,the techniques used,and extract comparableinformation from the image;and4.2.2 The end result is presented as a processed or workingcopy of the image.4.3 Avoid the introduction of artifacts that add misleadinginformation to the image or the loss of image detail that couldlead to an erroneous interpretation.5.Significance and Use5.1 Processed ima