ASTM E2825-12
(Guide)Standard Guide for Forensic Digital Image Processing
Standard Guide for Forensic Digital Image Processing
SIGNIFICANCE AND USE
Processed images are used for many purposes by the forensic science community. They can yield information not readily apparent in the original image, which can assist an expert in drawing a conclusion that might not otherwise be reached.
5.2 This guide addresses image processing and related legal considerations in the following three categories:
Image enhancement,
Image restoration, and
Image compression.
SCOPE
1.1 This guide provides digital image processing guidelines to ensure the production of quality forensic imagery for use as evidence in a court of law.
1.2 This guide briefly describes advantages, disadvantages, and potential limitations of each major process.
General Information
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Standards Content (Sample)
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Designation: E2825 − 12
Standard Guide for
1
Forensic Digital Image Processing
This standard is issued under the fixed designation E2825; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3.1.5 image, n—imitation or representation of a person or
thing, drawn, painted, photographed, and so forth.
1.1 This guide provides digital image processing guidelines
SWGDE/SWGIT Glossary
to ensure the production of quality forensic imagery for use as
evidence in a court of law.
3.1.6 image enhancement, n—any process intended to im-
prove the visual appearance of an image or specific features
1.2 This guide briefly describes advantages, disadvantages,
within an image. SWGDE/SWGIT Glossary
and potential limitations of each major process.
3.1.7 lossless, adv—descriptive term for encoding and de-
2. Referenced Documents
coding processes and procedures in which the output of the
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2.1 ISO/IEC Standard:
decoding procedure(s) is identical to the input to the encoding
ISO/IEC 10918-1:1994 Information technology—Digital
procedure(s). ISO/IEC 10918-1:1994
compression and coding of continuous-tone still images:
3.1.8 lossless coding, n—mode of operation that refers to
Requirements and guidelines (JPEG) (also published as
any one of the coding processes defined in this guide in which
CCITT Recommendation T.81 (1992))
all of the procedures are lossless. ISO/IEC 10918-1:1994
3
2.2 SWGIT Material:
3.1.9 lossless compression, n—compression in which no
SWGDE/SWGIT Glossary SWGDE and SWGIT Digital &
data are lost and all data can be retrieved in their original form.
Multimedia Evidence Glossary, updated June 8, 2012
SWGDE/SWGIT Glossary
3. Terminology
3.1.10 lossy, adv—descriptive term for encoding and decod-
3.1 Definitions:
ing processes that are not lossless. ISO/IEC 10918-1:1994
3.1.1 artifact, n—visual/aural aberration in an image, video,
3.1.11 lossy compression, n—compression in which data are
or audio recording resulting from a technical or operational
lost and cannot be retrieved in their original form.
limitation. SWGDE/SWGIT Glossary
SWGDE/SWGIT Glossary
3.1.1.1 Discussion—Examples include speckles in a
scanned picture or “blocking” in images compressed using the
3.1.12 noise, n—variations or disturbances in brightness or
JPEG standard.
color information in an image that do not arise from the scene.
SWGDE/SWGIT Glossary
3.1.2 compression, n—process of reducing the size of a data
file (see lossy compression and lossless compression). 3.1.12.1 Discussion—Sources of noise include film grain,
SWGDE/SWGIT Glossary electronic variations in the input device sensor and circuitry,
and stray electromagnetic fields in the signal pathway. It
3.1.3 grayscale image, n—continuous tone image that has
frequently refers to visible artifacts in an image.
only one component. ISO/IEC 10918-1:1994
3.1.13 original image, n—accurate and complete replica of
3.1.4 grayscale transformation, n—operation that modifies
the primary image, irrespective of media.
a single channel or component of image data (for example, a
SWGDE/SWGIT Glossary
single color).
3.1.13.1 Discussion—For film and analog video, the pri-
1 mary image is the original image.
This guide is under the jurisdiction of ASTM Committee E30 on Forensic
Sciences and is the direct responsibility of Subcommittee E30.12 on Digital and
3.1.14 primary image, n—firstinstanceinwhichanimageis
Multimedia Evidence.
recorded onto any media that is a separate, identifiable object.
Current edition approved May 1, 2012. Published October 2012. DOI: 10.1520/
E2825-12. SWGDE/SWGIT Glossary
2
Available from American National Standards Institute (ANSI), 25 W. 43rd St.,
3.1.14.1 Discussion—Examples include a digital image re-
4th Floor, New York, NY 10036, http://www.ansi.org.
3 corded on a flash card or a digital image downloaded from the
Available from Scientific Working Group on Imaging Technology (SWGIT),
http://www.swgit.org. internet.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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E2825 − 12
3.1.15 restoration, n—any process applied to an image that 5.2.1 Image enhancement,
has been degraded by a known cause (for example, defocus or 5.2.2 Image restoration, and
motion blur) to remove partially or totally the effects of that 5.2.3 Image compression.
degradation. SWGDE/SWGIT Glossary
6. Image Enhancement
4. Summary of Practice
6.1 Image enhancement is any process intended to improve
4.1 The original image shall be preserved. Any image
the visual appearance of an image.
processing
...
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