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Glossary: T

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Tagged-Image File Format
See TIFF
Technical metadata
See Metadata, technical
THD
See Total harmonic distortion
Thresholding
An image processing method that creates a bitonal (aka binary) image based on setting a threshold value on the pixel intensity of the original image. While most commonly applied to grayscale images, it can also be applied to color images. The threshold of image intensity (relative image lightness) is set manually at a…
See Also Bitonal digital image; Thresholding, adaptive
Thresholding, adaptive
Adaptive thresholding, also called dynamic or local thresholding, establishes the threshold level for determining whether to convert to white or black at a regional level. The region sampled and method of evaluation vary between applications. Adaptive thresholding at a pixel level (in comparison with neighboring pixels) can yield highly superior results compared to…
See Thresholding
Thumbnail image
A small, low resolution file normally used as a preview of an image. A thumbnail image is often linked to a higher resolution version of the same image.…
TIFF
TIFF is a file format for storing and exchanging bitonal, grayscale, and color images. The term is now used without reference to the original source phrase: Tag or Tagged Image File Format. Developed by Aldus as a universal format for desktop scanners in the 1980s, TIFF came under Adobe\'s control when Adobe acquired Aldus. …
See Also TIFF baseline; TIFF header
TIFF baseline
The TIFF 6.0 specification describes Baseline TIFF as "...the core of TIFF, the essentials that all mainstream TIFF developers should support in their products." Baseline TIFF is described in Part 1 of the specification.…
See Also TIFF; TIFF header
TIFF baseline tags
See TIFF header
TIFF extended tags
See TIFF header
TIFF header
The TIFF image format contains a flexible, extendable metadata structure based on a header that contains numerically tagged data fields. The baseline tags are listed and described in Part 1 (Baseline TIFF) of the TIFF 6.0 specification, where they are described as Required Fields. These 36 tags cover mainly technical metadata that any TIFF-specification compliant…
See Also TIFF; TIFF baseline
Tiled image
See Mosaic image
Tolerance
Allowable deviation from a specified value.…
Tone Reproduction Curve (TRC)
Generally considered to be synonymous with Tone Transfer Function. Technically, a single function that describes an object energy-to-displayed energy (i.e., reproduction") transformation. An OECF is technically not a tone reproduction curve as much as it is a tone encoding curve.…
Tone Transfer Function (TTF)
Any generic functional relation that describes the way light levels (or encoded light levels) are numerically transformed. Examples of tone transfer functions are a film's characteristic curve that describes how radiant energy is transformed into different levels of film density. Similarly, a gamma function or OECF describes how scene reflectances are related to 8-bit…
Total harmonic distortion
Although applicable to other waveforms, in the context of library- and archive-related digitization, THD is generally discussed in terms of sound. The total harmonic distortion of a signal is defined as the ratio of the sum of the powers of all harmonic components to the power of the fundamental frequency (the lowest frequency in a…
See Also Distortion; Noise
Track (audio)
A single stream of recorded sound with no location in a sound field. Although the term track has historically been used in the context of fixed media, e.g., "a four-track tape," this glossary\'s definition focuses on the processed signal and not the storage medium. One frequent use for track is in the context of…
See Also Channel (audio); Sound field; Multitrack (audio)
Transmission densitometer
See Densitometer
Transmissive object
An object that is intended to be, or is generally, viewed or used in a manner that allows light to pass through from one side of the object to the other. The viewing or use of the object is by way of the transmitted light. Examples of transmissive objects inlcude photographic slides and negatives.…
Transmissive scanning
Digital imaging of an object where light is transmitted through the object, generally a transmissive object such as a photographic slide or negative.…
Transmittance
The percentage that transmits through that object in relationship to the amount of light striking an object. The percentage of transmittance is inversely related to the optical density of the object.…
TRC
See Tone Reproduction Curve (TRC)
Tri-linear array
Three consecutive linear arrays of red, green, and blue sensitive sensor elements.…
TTF
See Tone Transfer Function (TTF)
TWAIN
Although represented in all upper-case lettering, the word TWAIN is not an acronym, and was derived from Rudyard Kipling's The Ballad of East and West which contains the line "and never the twain shall meet." TWAIN is a freely available open protocol that manages the communication between imaging devices and software applications. When a…