harmonics and the screen door effect

[Jonathan Wienke]

I opened up one of my own files in PixelClarity. It's hard to understand how exactly to use this.

After clicking on "reinterpolate image" in this program, the left-side screenshot looks much better than the right-side original.

Right now, what you have is just a tech demo; I put it up to get feedback on the quality of the interpolation algorithms I'm using for upsizing and downsizing. It doesn't have a save option enabled yet. The goal is for the resized image to be as sharp as possible with the least aliasing regardless of the rescaling percentage.

[BartvanderWolf]

[...]you're better off using a decent resampling algorithm that doesn't require such stupidity in the first place.

I fully agree. It's amazing that after all these years there is still no option for a slower but much  better behaved downsampling algorithm in Photoshop.

Bicubic Sharper is one of the best available options in Photoshop, especially if you don't do any sharpening after resampling.

I disagree on the 'one of the best' part. With regards to aliasing it is worse than regular bicubic (as implemented in Photoshop).
I did a number of comparisons several years ago that show the potential differences/risks:
http://www.xs4all.nl/~bvdwolf/main/foto/down_sample/down_sample.htm
 and for some less theoretical examples on a real image:
http://www.xs4all.nl/~bvdwolf/main/foto/down_sample/example1.htm
Especially the aliasing of the sunscreens will be what probably can be seen in the OP's 'screen door' effect.

Cheers,
Bart