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Brief Overview to Resampling within Affinity Photo


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There is quite some confusion about how Resampling works in Affinity Photo, and at what places the user can manage the settings / parameters:

  1. View Quality in Preferences->Performance
  2. Pixel Art Resize
  3. Rasterising layers after usage of Move Tool / Transform Panel
  4. Resizing Document
  5. Exporting Documents

Resampling is the algorithm used to deal with different resolution (DPI / PPI) of documents, document layers, display size, and exported files.

It is unavoidable - we cannot assume that document and displays have always the exact same resolution and physical size. Resampling is used when using zoom, using documents having multiple layers, rendering vector objects to pixel displays etc.

It might be that you never noticed anything about resampling during regular edits. But in case your are using zoom level above or below 100%, apply sharpening or noise filters, use layers with transparency, rotate layers or scale objects to a resolution that differs from the document resolution, resampling will definitely start to have a visible impact, often with surprising results.

In this tutorial, I want to give a brief overview at what places in Photo you have settings or other ways to influence how resampling affects your document, or document rendering.

 

  1. View Quality in Preferences->Performance
    • Affects only how the document is rendered on screen, when opened in Photo
    • Does not affect resize, rasterise, export operations
  2. Resizing Document
    • A range of 5 methods are offered which have specific use-cases (see help for details)
    • All layers within the document are affected (specifically bitmap layers and mask layers).
    • Vector layers are impacted indirectly: only the positions of nodes, and stroke width gets scaled accordingly. Resizing does not cause resampling for vector objects.
  3. Pixel Art Resize
    • Allows to resize a document 
    • Focus on scale-up by factor 2, 3, or 4 (not usable for scale-down)
    • 2 specialised resample methods offered, which intend to keep hard edges and corners during scale-up
  4. Rasterising layers after usage of Move Tool / Transform Panel
    • Whenever you rasterise individual layer inside Photo, Bilinear Resampling is always used, for up-scaling and down-scaling
    • For up-scaling, this will create blurriness (softening)
    • For down-scaling, document pixels will get a weighted average of pixels in layers in general.
    • If you want to scale individual layers using a different resample method, you need to copy/paste it into a new temporary document, Resize / Resample the temporary document, and copy/paste the result back into the original document.
    • Bilinear Resampling can create false colours for structures who become smaller than 1px, especially when used in combination with blend ranges on source layers
  5. Exporting Documents (to bitmap / raster formats)
    • A range of 5 methods are offered which have specific use-cases, same as resize document (but excluding Pixel Art Resize)
    • The document gets flattened (rasterised to pixel format), using the selected resample method
    • Vector layers get rasterised and resampled
    • A document gets always resampled for export, even if the export size is identical to document size. Normally, you will see no difference (to screen rendering) if you are using default Bilinear for both View Quality and export resample method. 

General Remarks about Resampling

  • Resampling is unavoidable, and the different methods have their specific pros and cons. Choose wisely based on your artistic intentions (natural looking photos, pixel art, scientific documents, text, focus on sharpness, focus on preserving colors and lightness in average, focus on preserving fine details as much as possible, ...)
  • Some operations like noise and sharpening depend on the document resolution. If you export at different sizes, either smaller or larger, you can get unintended and surprising results. For highest accuracy, apply noise or sharpening after resizing, as last step before exporting, and keep the document size for export. Always use 100% (or higher) zoom level to inspect the results of noise or sharpening effects.

 

1687013939_ResampleinAffinityPhotoV2.thumb.png.4fce753dd03664644704e91b1b6d649b.png

 

Edited by NotMyFault
Corrected parts wrt Pixel Art Resize

Mac mini M1 A2348

LG34WK950U-W, calibrated to DCI-P3 with LG Calibration Studio / Spider 5

iPad Air Gen 5 (2022) A2589

Special interest into procedural texture filter, edit alpha channel, RGB/16 and RGB/32 color formats, stacking, finding root causes for misbehaving files, finding creative solutions for unsolvable tasks, finding bugs in Apps.

 

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  • 3 weeks later...

How can you do a Pixel Art resize only to a layer?

On 12/19/2022 at 11:36 AM, NotMyFault said:
  • Allows to resize individual layers inside a document (independent from document resolution)
  • Focus on scale-up (not scale-down)
  • Does not affect other layers

 

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6 hours ago, Zero1 said:

How can you do a Pixel Art resize only to a layer?

 

Thanks for spotting this error. Pixel Art Resize affects the whole document with all layers, too.

I did most tests on iPad, and i got the false impression only the active layer was resized. maybe caused by redraw issues.
 

Verifying again on Mac and iPad proved me wrong. I will update the tutorial.

Mac mini M1 A2348

LG34WK950U-W, calibrated to DCI-P3 with LG Calibration Studio / Spider 5

iPad Air Gen 5 (2022) A2589

Special interest into procedural texture filter, edit alpha channel, RGB/16 and RGB/32 color formats, stacking, finding root causes for misbehaving files, finding creative solutions for unsolvable tasks, finding bugs in Apps.

 

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