Editing WoW:SetTexCoord Transformations (section)

=== Texture coordinates ===
A Texture frame is used to display all or part of an image. It has an arbitrary location, size, and scale, and appears as a rectangular area on the screen with vertical and horizontal edges, just like any other frame. We'll use the term ''Texture Coordinates'' to refer to a location within the frame, where (0,0) is the lower left corner, (1,0) is the lower right corner, (0,1) is the upper left corner, and (1,1) is the upper right corner. "Texture" will always have an initial capital, for consistency with the name of the frame type in the API. Each screen coordinate within the bounds of the Texture on screen can be mapped into a Texture frame coordinate within the box from (0,0) to (1,1).