Anti-aliasing and Gamma Compression
Digital images are usually stored in a gamma-compressed format, but an optical anti-aliasing filter is linear. So to downsample an image in a way that would match optical blurring, one should first convert it to a linear format, then apply the anti-aliasing filter, and finally convert it back to a gamma compressed format. Computing anti-aliasing directly on the gamma-compressed image will lead to bright details (such as a cat's whiskers) becoming visually thinner, and dark details (such as tree branches) becoming thicker, relative to the optically anti-aliased image. Almost all image editing software, including Final Cut Pro, Adobe Photoshop and GIMP, process images in the gamma-compressed domain.
Read more about this topic: Spatial Anti-aliasing
Famous quotes containing the word compression:
“Do they [the publishers of Murphy] not understand that if the book is slightly obscure it is because it is a compression and that to compress it further can only make it more obscure?”
—Samuel Beckett (1906–1989)