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This is obviously not a question limited to APhoto, but after editing and (substantial) cropping of jpg images, is there any point in upscaling to something approaching the original resolution before resaving as a jpg?

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Hi @henryg,
Welcome to Affinity Forums :)
No, there's no point in upscaling unless you really need a bigger image/output. Any downscaling or upscaling always affects image quality negatively because you are either interpolating or removing pixels from the original image which affects its sharpness/definition. If you really have to upscale use a proper resampling algorithm (depends on the type of image) to get a better result.

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  • 2 weeks later...

The appropriate algorithm doesn’t really depend on the file format (e.g. JPEG, PNG, or TIFF). Generally speaking, bilinear or bicubic resampling is adequate for downscaling but Lanczos3 (separable or non-separable) is better for upscaling.

When choosing a file format for export, what’s important is the type of image; i.e. whether it’s a photograph or a graphic comprising large areas of solid colour, with or without text. Even a small amount of JPEG compression will introduce artefacts at the boundary between blocks of solid colour, an effect which is especially noticeable around the edges of any text in the image.

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Affinity Designer/Photo/Publisher for Windows 1.10 • Windows 10 Home/Pro
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Thank you.

Mostly pictures of stamps. Some are simple graphics while others are much more complex illustrations.
I will try with the Lanczos3 and compare.

 

iMac mid-2017
3,6 Ghz / 32G

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3 minutes ago, henryg said:

Any guidance on when to use Lanczos3 separable or non-separable? Googling didn't come up with anything much.

21 hours ago, Alfred said:

The appropriate algorithm doesn’t really depend on the file format (e.g. JPEG, PNG, or TIFF). Generally speaking, bilinear or bicubic resampling is adequate for downscaling but Lanczos3 (separable or non-separable) is better for upscaling.

Upscaling means enlarging.

MacBook Pro (13-inch, Mid 2012) Mac OS 10.12.6 || Mac Pro (Late 2013) Mac OS 11.6.8

Affinity Designer 1.10.5 | Affinity Photo 1.10.5 | Affinity Publisher 1.10.5 | Beta versions as they appear.

I have never mastered color management, period, so I cannot help with that.

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11 hours ago, henryg said:

Any guidance on when to use Lanczos3 separable or non-separable? Googling didn't come up with anything much.

 

Due to the fact that Boris Johnson is now was our Prime Minister, punctuation, spelling and grammar will never be worried about ever again.  We now have far bigger problems to be worried about.

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