Re: [Gimp-developer] image quality degraded due to scaling

[Burnie West <west ieee org>]

On 02/10/2012 02:57 AM, smit sanghavi wrote:
> Hi,
> While using GIMP, I noticed that when an image is scaled initially, and then 
> rescaled after making some changes, the quality of the image reduces. It is 
> very significant when the image is scaled by a large extent.
> I understand that this is due to the data loss that occurs during scaling. But 
> i was wondering if there was any alternative approach to avoid this problem.
My approach to avoiding this problem is to scale up  in binary steps (2,4,8) a 
lot first, then modify the image, then scale down to the final target size. This 
sort of works around the limited resolution by providing a couple of extra bits 
to average with on the down-scale step. It seems to work better if the scaling 
mode is set to Sinc (Lanczos 3) rather than the default cubic mode. Haven't 
really explored it much, though.

  -- Burnie