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Truevision TGA, version 2.0

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Format Description Properties Explanation of format description terms

Identification and description Explanation of format description terms

Full name Truevision TGA File format, version 2.0
Description

A simple raster format for individual images first established by Truevision, Inc. in 1984 and extended in 1989. Designed for use on systems that use MS-DOS color applications, TGA is the native format of Truevision's TARGA (Truevision Advanced Raster Graphics Adapter) boards, which were some of the first graphic cards for IBM-compatible PCs to support truecolor display (most often defined as 24-bit RGB color encoding). TGA supports mapped/indexed color and RGB color, with additional support for transparency information (sometimes referred to as alpha channel, as in RGBA color space). Transparency information permits images to be superimposed over other data, e.g., additional images, text layouts, or video, and permits effects like cross-fading between graphic images and video, etc.

TGA images may be encoded at 8, 16, 24, or 32 bits per pixel (as mapped/indexed color, RGB, or RGBA). TGA supported 24-bit color before such support was available in the TIFF format, and this helped establish the format's popularity during the 1980s.

Features added in version 2.0 include specification of pixel aspect ratio (providing more explicit support for square and non-square pixels), color correction tables, an embedded thumbnail image (termed postage-stamp in the standard), and some very basic metadata elements (such as author, software, date/timestamp, job number, comments). A developer area provided a mechanism for including additional information.

Production phase Most often an initial-state or middle-state format.
Relationship to other formats
    Has earlier version TGA_1, Truevision TGA, version 1.0

Local use Explanation of format description terms

LC experience or existing holdings None.
LC preference Not a preferred format. Lossless transformation to TIFF_6 recommended for final-state works.

Sustainability factors Explanation of format description terms

Disclosure Proprietary. Truevision used to make the specification available. Truevision was acquired by Pinnacle Systems in 1999. The TGA specification does not seem to be available from the Pinnacle Systems website.
    Documentation The specification Truevision TGA, File Format Specification, Version 2.0 is available in various forms on the Internet, e.g., as PDF [http://www.dca.fee.unicamp.br/~martino/disciplinas/ea978/tgaffs.pdf].
Adoption This format was widely used by graphics specialists before most personal computers had graphics displays. As an industry standard, it is not as widely supported as PCX or TIFF formats. TGA (versions 1.0 and 2.0) have retained popularity for computer graphics professionals and video-game developers as a simple format that supports high bit-depth (up to 32 bits per pixel) and transparency. It is widely supported by high-end paint programs and ray tracing packages. Used in particular for "texture" files used for image composition and 3D-rendering techniques.
    Licensing and patents Technically proprietary, but not exploited.
Transparency Licensing and patent claims
Self-documentation Minimal support for embedded metadata.
External dependencies None
Technical protection considerations None

Quality and functionality factors Explanation of format description terms

Still Image
Normal rendering Good support.
Clarity (high image resolution) Support for images with high spatial resolution. Support for RGB (plus transparency) color space or mapped (indexed) color and bit depth of 8, 16, 24, or 32 bits per pixel.
Color maintenance Designed primarily for use on PC video displays using RGB colorspace. No support for ICC color profiles.
Support for vector graphics, including graphic effects and typography No support for vector graphics.
Functionality beyond normal rendering Support for transparency.

File type signifiers Explanation of format description terms

Tag Value Note
Filename extension tga
Recommended in TGA version 2 specification.
Mac OS file type TPIC
Documented in TGA version 2 specification.
File signature ASCII: TRUEVISION-XFILE
In TGA version 2.0 files, this signature is in bytes 8-23 of the TGA footer, which comprises the last 26 bytes in the file.

Notes Explanation of format description terms

General  
History Truevision defined the first version of its TGA file format in 1984 for use with its first videographics products, including video boards for PC displays. In 1989, Truevision introduced TGA version 2.0. The new version was designed to allow software that worked with version 1.0 to work with version 2.0 images (ignoring the added functionality). However, neither of the two versions is a strict subtype of the other.

Format specifications Explanation of format description terms


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Last Updated: 09/13/2013