"Ewald R. de Wit" wrote:
> Anyway, today I went over the Gimp sources and noticed how complicated
> the tile architecture makes things and I couldn't help wondering why
> the heck it was put in. All it seems to do is to give you an order of
> magnitude slower speed when dealing with large images. And large
> images were supposed to be the very reason for a tiling architecture.

Performing 'linear' operations on an image (such as color correction) is
not much slower on the tiled architecture. But 'non-linear' access to
the image (such as 90 degree rotations) is terribly slow when the image
has been swapped out. As far as you read the data on the same order it
was stored (row order, usually), the disk heads will not have to move
too much, because you are reading data from adjacent positions. But if
you try to read the data in another order (column order, on the 90
degree rotation example), the heads of the disk must go forward and
backwards to find the data. Storing the data using a tiled order solves
this probblem, as you can read a whole tile into memory each time.


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