What is TGA (Truevision TGA)?

How TGA Works

A TGA file, also called TARGA or Truevision graphics format, begins with a compact fixed header that describes the image. This header records the image type, the width and height in pixels, the number of bits per pixel, and an image descriptor byte. The descriptor is important: it holds the number of alpha channel bits and two orientation flags that state whether the pixel data starts at the top or bottom and the left or right of the image. Because orientation is signaled rather than fixed, a decoder must read these flags to display the picture the right way up.

After the header, a TGA file may contain an optional color map (palette) for indexed images, followed by the pixel data itself. TGA supports several depths, commonly 8-bit indexed or grayscale, 16-bit, 24-bit true color, and 32-bit true color with an 8-bit alpha channel. The 32-bit mode is one of the format's most useful traits, since it stores a full per-pixel transparency mask alongside red, green, and blue.

Pixel data can be stored uncompressed or with a simple run length encoding (RLE) scheme. RLE walks the image and replaces consecutive runs of identical pixels with a count and a single pixel value, which shrinks images that contain flat areas of solid color. On photographic or heavily detailed images the RLE gain is small, and in some cases the compressed file is barely smaller than the raw version.

A later revision of the specification added a footer at the end of the file plus an optional extension area and developer area. These can carry metadata such as author, a timestamp, a gamma value, and a thumbnail. Files that include the footer are sometimes called "new TGA," while older files without it are still valid and widely readable.

History and Standardization

TGA was created by Truevision Inc. in the mid to late 1980s. It was designed as the native image format for the company's TARGA and VISTA graphics boards, which were among the first products to bring true-color, 24-bit capture and display to personal computers at a time when most PC graphics were limited to a handful of colors.

The name TARGA is often explained as a reference to the Truevision Advanced Raster Graphics Adapter. Because the format was tied to professional capture hardware, it found an early home in video, broadcast graphics, and desktop imaging, where retaining full color fidelity mattered more than small file size.

TGA was never standardized by a formal international body in the way that JPEG or PNG were, but its specification was published and became a stable de facto standard. That published spec, including the later footer and extension additions, is why so many graphics tools can still read and write TGA decades after the original hardware disappeared.

TGA Compared to BMP, PNG, and PSD

Compared to BMP, TGA is more capable. Both are simple raster formats, but classic BMP historically lacked a practical alpha channel, while TGA offered a clean 32-bit mode with true per-pixel transparency. TGA's optional RLE also gives it a modest size advantage over fully uncompressed BMP on images with flat color regions.

Compared to PNG, TGA is weaker on compression. PNG uses the DEFLATE algorithm, which is far more effective than TGA's basic RLE, and PNG also supports lossless color with full alpha. For most modern purposes where a lossless file with transparency is needed, PNG produces smaller files and is more universally supported in browsers and applications.

Compared to a layered format like PSD, TGA is intentionally flat: it stores a single composited image with no layers, masks, or editing history. That simplicity is exactly why TGA endured in game development and 3D texturing pipelines, where a straightforward true-color image with a reliable alpha channel is often all that a texture needs. TGA has been largely superseded by PNG for general use, but it is still seen in older and specialized asset workflows.