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libvips / nip2

A spreadsheet-like GUI for libvips.
https://libvips.github.io/libvips/
GNU General Public License v2.0
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v7.36.x, Windows(XP), Interpolation [res:feature,no bug] #36

Closed MvGulik closed 10 years ago

MvGulik commented 11 years ago

It seems to me that something is a miss with the interpolation options. ?

Re-scaled a 5kx5k image to 100x100 and compared the output on the different interpolation options, and there all identical. (except for the "nearest" option of course.)

Also did a quick visual compare by eye with v7.34.0, and only the last interpolation option "upsmooth:..." shows a clear visual difference from the other interpolation options. (the other interpolation options seem to return identical results. "nearest" excluded.)

jcupitt commented 10 years ago

Downsizing is done in two steps: a block shrink to the nearest integer factor above the target size, then interpolation to the final size with the selected interpolator.

Your 5kx5k image will have been block-shrunk to 100x100 directly with a 50 x 50 average, then left untouched by the interpolator. Try sizing down to 101 x 101, you should see some small differences then.

You'll see more of a difference on upsizing. That simply uses the interpolator.

MvGulik commented 10 years ago

Aha, I did not know that. (working as you explained.) Thanks.

Sorry for the false alarm. (closing)