ThumbsPlus

All forums => ThumbsPlus v7-v9 Questions => Topic started by: JayB on 2013-07-29 21:46:32

Title: Grainy Resizing?
Post by: JayB on 2013-07-29 21:46:32

I'm resizing 4k x 2k photo down to 800x600 and getting real grainy results. With past versions (V8+V7), I have never had this result so I'm a little confused.

Anyone else running into this?

Title: Grainy Resizing?
Post by: Daan van Rooijen on 2013-07-29 23:32:06

In the Resize dialog, set the 'interpolation' option to Downsample or Bi-Cubic. If that doesn't help, are you sure that it's a 24-bit image?

Title: Grainy Resizing?
Post by: JayB on 2013-07-30 18:07:19

The images are 24-bit.
The interpolation was set to bi-cubic and giving me real grainy images.

I switched it over to down sample and it seems to be a lot better.
THanks!

Title: Grainy Resizing?
Post by: mschnell on 2013-08-03 08:58:52

While "Bicubic" usually works rather well for downsizing, with pictures that include narrow lines (e.g. hair, high voltage wires, ...) I often get results with an unnatural touch (fuzzy highlights added etc).

This can be prevented when applying some blur filter before resizing.

That is why I often use the "Lanczos" algorithm provided by the free Irfanview software. Same usually works perfect for downsizing.

It would be great if TP would provide this algorithm out of the box or as a pluging.

-Michael

Title: Grainy Resizing?
Post by: Daan van Rooijen on 2013-08-03 23:40:40

> It would be great if TP would provide this algorithm out of the box or as a pluging.

Agreed, Lanczos would be great to have! And an Mspline-like option for upsizing would be great too.

btw, for the OP: it's generally a good idea to run Image | Filter | Select Filter | Sharpen | Unsharp Mask after you've used Resize to make an image smaller. Basically, this will restore the sharpness that was lost in the resizing. Once you have used a filter, you can simply press Ctrl-F to apply the same filter again (on another image).

Title: Grainy Resizing?
Post by: mjgraves on 2013-08-06 17:09:53

I've always wondered why resizing in Photoshop looks better than resizing in ThumbsPlus, even when both are using bicubic interpolation?

In the bad old days of DOS I used Image Alchemy, which was a command line driven batch file converter that could do a lot of transformations. It allowed the selection of one of a dozen different scaling routines. At the time such was critical because PCs were so slow and memory constrained. IA could RIP a postscript vector file to vast raster dimensions to feed a printer or plotter.

Michael