Loss of quality when resizing picture

[tmmls]

Hi,

 

With this post I would like to submit a bug.

 

When resizing a picture using the "Document" > "Resize Document" option, the picture will lose more quality then in using the same setting in Adobe Ph. I've tried multiple settings.

 

In the attached picture, I used "bicubic" resampling, In Aff. Photo as well as in Photoshop.

 

Kind regards

 

 

 

 

[TonyB]

That's not our experience but Lanczos 3 should always give a superior result when reducing size.

[MikeW]

Do note that Photoshop has an overly soft on-screen image. Assuming the bicubic routines are roughly the same, an image in PS will always appear softer than in other applications. This effect has always been this way and is one reason I receive images that have been processed in PS by professional photographers that are over sharpened--they appear in PS fine, but not when the hit the press output PDF or in other applications that do not overly soften their display of images.

 

I'm not saying that this is why your particular image appears to have the difference it does.

[NFG]

It's apparently a Windows version bug:

https://forum.affinity.serif.com/index.php?/topic/28897-rescaling-quality/?p=140380

[jorismak]

One Bicubic isn't the other Bicubic :P.

 

There are two parameters to the algorithm commonly known as 'bicubic' resize, which can have a pronounced affect on the amount of blurring, sharpness, haloing, ringing.. If Affinity picks settings that are 'too sharp' compared to Photoshop's it will jump out. But to be honest, Lanczos is often even sharper (and more ringing).

 

You are viewing at 200% and the images look the same size, so I expect your windows scaling is set at the regular 100% (i.e. not scaled).

 

That means that both Affinity and Photoshop are blowing up the image when viewing. How do they blow it up? You know that? Because I'm betting there is the difference.

 

I'm guessing Affinity blows up the image by using regular point-resize in this case, in other words, duplicating of pixels, which causes the very pixelated look (but stays kinda true to what is actually in your image data).

 

Photoshop is zooming in by using some Bilinear or Bicubic algorithm, so it appears better, but it's fake! That's not your image at all. One of the reasons they always say to judge when at 100%. Downsizing / upsizing causes artifacts... or less strong: There is no perfect downsizing or upsizing, there is always some thing 'off' or 'made up'. So when you're judging images at 200%, you're actually judging the zoom-in-preview effect from Photoshop vs the zoom-in-preview effect from Affinity... You're not judging your image's pixels at all!

 

As a proof of point (and I'm hoping I'm actually right in this :P ) try saving both result-images as .tif files, and load them in another program like IrfanView. View them there at 200%. Now you're using the same viewing-tool, and I bet they suddenly look a lot more similar.

 

(maybe I'll try this test for myself now :))

 

EDIT:

That's a whole lot of text I was typing, but while it all might be true (ahem), it's apparently not the problem in this case. I just did my own test (after installing latest .38 beta) and indeed something is off. The output of Affinity seems way more pixelated than it should be, even when saved and viewing the result in the same program.

 

1st is Affinity 'Bicubic': 

2nd is Photoshop 'Bicubic sharper': 

 

Both are 300% crops, so both are  a bit pixelated, but the Affinity one is just _too_ sharp for a simple resize! As if there is some unsharp masking done after the resize, or the 'b,c' parameters from Bicubic are set way too high.

 

The black line inside the white hand actually ends up _thinner_ than the original... this is way too much sharpening-effect for a resize / resample.

[Opera]

Hi jorismak, the difference in deed is significant. Affinity Bicubic looks a bit stuttering .

[MattP]

Hi Guys, as was established in post #5 by NFG, this is simply a bug in the Windows version - I suspect that parameter has not been correctly wired up to the backend so the resize will look poor because it isn't using the sampler you just told it to! This will obviously be resolved very soon. Sorry for any inconvenience in the meantime :)