One of several data values persent in each pixel. Examples include red, green, blue, alpha, etc. The data in one channel of a pixel may be represented by a single number, whereas the pixel as a whole requires one number for each channel.


A client (as in “client application”) is a program or library that uses OpenImageIO or any of its constituent libraries.

Data format

The representation used to store a piece of data. Examples include 8-bit unsigned integers, 32-bit floating-point numbers, etc.

Image File Format

The specification and data layout of an image on disk. For example, TIFF, JPEG/JFIF, OpenEXR, etc.

Image Format Plugin

A DSO/DLL that implements the ImageInput and ImageOutput classes for a particular image file format.

Format Plugin

See image format plugin.


Data about data. As used in OpenImageIO, this means Information about an image, beyond describing the values of the pixels themselves. Examples include the name of the artist that created the image, the date that an image was scanned, the camera settings used when a photograph was taken, etc.

Multi-part image / multi-part file

This is what OpenEXR calls a file containing multiple subimages.

Native data format

The data format used in the disk file representing an image. Note that with OpenImageIO, this may be different than the data format used by an application to store the image in the computer’s RAM.


One pixel element of an image, consisting of one number describing each channel of data at a particular location in an image.


See image format plugin.


A single horizontal row of pixels of an image. See also tile.

Scanline Image

An image whose data layout on disk is organized by breaking the image up into horizontal scanlines, typically with the ability to read or write an entire scanline at once. See also tiled image.


Some image file formats allow the storage of multiple images in each file. These are called subimages in OpenImageIO. Note that in OpenEXR, these are called multi-part files.


A small, lower-resolution preview image that is stored in an image file, in addition to the main image that the file represents. Not all image file formats support thumbnails.


A rectangular region of pixels of an image. A rectangular tile is more spatially coherent than a scanline that stretches across the entire image — that is, a pixel’s neighbors are most likely in the same tile, whereas a pixel in a scanline image will typically have most of its immediate neighbors on different scanlines (requiring additional scanline reads in order to access them).

Tiled Image

An image whose data layout on disk is organized by breaking the image up into rectangular regions of pixels called tiles. All the pixels in a tile can be read or written at once, and individual tiles may be read or written separately from other tiles.

Volume Image

A 3-D set of pixels that has not only horizontal and vertical dimensions, but also a “depth” dimension.