[Gimp-user] scaling

[David Gowers]

On 9/25/07, Andrew <ald2 at arrakis.es> wrote:
> The Wikipedia article certainly was over my head.
>
>  From what I read on the Gimp bug page lanczos scaling is not yet
> perfect. (But then what is?)
>
> I have to upscale images from 16M to 48M and it seems the client takes
> them apart and looks at them through a microscope and rejects them if
> there are signs of sharpening or interpolation artefacts.
>
> So far as I can see, my Gimp (2.4.0-rc2) does have lanczos downscaling

I know. That is why I made a point of saying it doesn't. It has some
strange facsimile of Lanczos downscaling. If you compare ImageMagick's
implementation with GIMP's, you can see a clear difference (and that
ImageMagick gives better looking results.)

For your requirements, if you don't need to do much interactive
processing, I recommend ImageMagick. For a start, it has many
different interpolation filters (specified using '-filter FILTER'
commandline parameter) that you can try for image scaling, compared to
GIMP's three. I'm certain that one of them will obtain better results
for your particular situation.