Moire effect when resizing an image

[Alex_M]

Hi,

I'm getting moire effect on walls with fine wallpaper texture when resizing the image. I tried all 5 resample algorithms with no luck. Good thing I have a spare copy of Photoshop. I tried resizing the image there in the same way and this problem doesn't happen with Photoshop.

Please see attached the files so you can check for yourself. I appreciate your help!

image.tiff

image_downsampled_600px_bicubic_affinityPhoto.tiff

image_downsampled_600px_bicubic_Photoshop.tiff

[markw]

Hello Alex,
Very strange?
I just tried down-sampling your image and all went well for me. See attached.
I’m on a Mac, not sure if that’s significant or not?

Downsampled_bicubic_600px_APhoto_1.7.3.tiff

[firstdefence]

It looks like the Photoshop version retains more contrast and the Affinity version is duller but the pixels stay the same.

[Alex_M]

I'm on Windows.

[Alex_M]

Anyone? How do I fix this?

[Callum]

I'm not getting this effect on Windows or Mac I'm afraid. Please could you provide a screen recording of you recreating the problem so I can make sure I am doing the same thing as you?

[firstdefence]

What screen are you using, I wonder if this is a consequence of the screen seeing as how everyone doesn't appear to be getting the same view as you Alex

[MikeW]

I get the exact same problem using APhoto. Also using Windows. 

[Jowday]

I don't. Results are inferior (slightly blurred with poor micro contrast) compared to those resized in Photoshop but apart from that no moire.

From Affinity Photo 1.7 and Adobe Photoshop CC 2020

image_downsampled_600px_bicubic_affinityPhoto_mine.tiff

image_downsampled_600px_bicubic_Photoshop_mine.tif

Originals:

image_downsampled_600px_bicubic_Photoshop.tiff

image_downsampled_600px_bicubic_affinityPhoto.tiff

[firstdefence]

After playing about with various settings and monitoring the histogram of the Adobe Photoshop downsampled file, the closest I can match to the Adobe Photoshop histogram on the original and downsample in Affinity Photo is to use Lanczos 3 (separable) and apply a live high pass filter set to approx 16px, this mimics the histogram of the Adobe Photoshop downsampled file fairly closely.

 

[lacerto]

(...)

[Jowday]

1 hour ago, Lagarto said:

To me it seems that the Affinity Photo resampled version you had attached in the original post was produced with the default bilinear algorithm rather than with the bicubic method. I could reproduce this with the original image and the resulting image really has clear vertical streaky artifacts throughout the image, similarly as in your attachment. But when I used bicubic method, the results are similar as with PS.  

Yes, you are right.

comparison.tif

 

[Alex_M]

 

On 2/14/2020 at 12:44 AM, Lagarto said:

To me it seems that the Affinity Photo resampled version you had attached in the original post was produced with the default bilinear algorithm rather than with the bicubic method. I could reproduce this with the original image and the resulting image really has clear vertical streaky artifacts throughout the image, similarly as in your attachment. But when I used bicubic method, the results are similar as with PS.  

That's strange. I can swear that the first time I tried the other resamplers it wasn't working, but now the moire is gone with bicubic and lanczos 3. Go figure. Thanks all for your help!