Copied from TechnicalIntroduction.pdf at OpenExr.
An OpenEXR file may not have pixel data for all the pixels in the display window, or the file may have pixel data beyond the boundaries of the display window. The region for which pixel data are available is defined by a second axis-parallel rectangle in pixel space, the data window. Examples:
- Assume that we are producing a movie with a resolution of 1920 by 1080 pixels. The display window for all frames of the movie is (0, 0) - (1919, 1079). For most images, in particular finished frames that will be recorded on film, the data window is the same as the display window, but for some images that are used in producing the finished frames, the data window differs from the display window.
- For a background plate that will be heavily post-processed, extra pixels, beyond the edge of the film frame, are recorded and the data window is set to (-100, -100) - (2019, 1179). The extra pixels are not normally displayed. Their existence allows operations such as large-kernel blurs or simulated camera shake to avoid edge artifacts.
While tweaking a computer-generated element, an artist repeatedly renders the same frame. To save time, the artist renders only a small region of interest close to the center of the image. The data window of the image is set to (1000, 400) - (1400, 800). When the image is displayed, the display program fills the area outside of the data window with some default color.
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