Affinity Photo--resampling twice?

[Nancy6107]

I've been reading posts about upsampling because I want to find which method to choose to get the best results. However, I notice that you choose a resample method when you resize a document, and then again when you export it for printing or viewing. Is the file being resampled again? If I select Bicubic when I resize, this doesn't necessarily come up as the choice when I export--the export resample is the method I used last time and I have to change it to Bicubic.

Thanks,

Nancy

[NotMyFault]

Hi Nancy,

resampling in this context is used specifically for the process of resizing a document, meaning changing the pixel dimensions (height or width in number of pixels), and calculating the resulting color values (R / G B / A ) of every "new" pixel by the selected method, using a wheighted average of "old" pixels.

Every time you ask for resampling explicitely bei either

• Document->resize Document with "resample" checked
• or File->Export AND changing the pixel size

it will be resampled.

So if you export, but do not change the pixel size, export will not re-sample.

But you image will be transformed during export by other methods in addition to resampling, like adjusting the R G B values by dithering to reduce the color depth from 32/16 bit to 8 bit, or a fixed palette in case of GIF format.

Assuming you resize only to reduce the pixel dimensions (downscale), my general advise is to not use resampling at all during normal edit, and only resample during export, as every resample impacts and might reduce image quality.

In case of resampling used to increase resolution (upscale), please disregard this comment and have a look at the comment below.

Resampling is only required in very specific situations, and otherwise completely superfluous for simple edits.

 

Regards,

Timo

Edited March 5, 2021 by NotMyFault
added distinction upscale/downscale

[Nancy6107]

Thank you for the explanation, Timo. I was talking about doing it to make my document larger, but from what you say it sounds as if I can wait until I am exporting and just increase the pixel size then--and choose my resample method. That is good to know. I've copied your explanation into my notes for future reference.

Take care,

Nancy

[NotMyFault]

Hi Nancy,

oh i did not expect that, sorry:

• I was talking about doing it to make my document larger,

In this case, you should do the resize in the beginning of the editing process. But it really depends on your raw images and the intended result how to continue to edit the document:

• If you are a hobby detective and want to enlarge small details or printed text, you need to sharpen the upscaled image heavily e.g. using highpass, unsharp mask, brightness & contrast, or even HDR / tone mapping, clarity etc.
• In case of natural objects like old portrait photos or landscapes, you may need to selectively smooth OR sharpen, so combining diferent techniques and using masks.

[Nancy6107]

Thanks for clarifying that. I don't do it often--mostly I am exporting a smaller version, and I have been resampling only when I export, not earlier.

Nancy

[lepr]

6 hours ago, Nancy6107 said:

I notice that you choose a resample method when you resize a document, and then again when you export it for printing or viewing. Is the file being resampled again?

Objects of type Pixel will be resampled twice in your scenario.

Resize document with resampling: Pixel objects will be resampled but Image objects will be non-destructively scaled.

Scaled raster export: Pixel and Image objects will be resampled.

Non-scaled raster export: non-destructively transformed Pixel and Image objects will be resampled.

 

(Affinity Designer's document resizing (see Dimensions tab of File > Document Setup) is entirely non-destructive and the control for a resampling method serves no purpose.)