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Posted (edited)

Hi,

when adding an add noise live filter, nest it into a group, placed atop a layer with partial transparency, it impacts the alpha channel in a unpredictable and unwanted way.

The resulting alpha is expected to be constant 0,75 / 191 after layer blending for all pixels.

The observed alpha value is scattered around 191, from 172 to 212.

image.thumb.png.0efe85e6e48df31837c599e3a117dfd9.png

 

image.thumb.png.693bedddc487f5b42db873a560071f1b.png

Mitght be related to my other post, might be a new issue.

 

 

image.png

add noise alpha bug.afphoto

 

 

Here a chart what would be expected (alpha mapped to blue channel to make it visible in Histogram)

image.thumb.png.f64479088d9c47ca9c8a6517f01d9564.png

Edited by NotMyFault
added histograms

Mac mini M1 A2348 | MBP M3 

Windows 11 - AMD Ryzen 9 5900x - 32 GB RAM - Nvidia GTX 1080

LG34WK950U-W, calibrated to DCI-P3 with LG Calibration Studio / Spider 5 | Dell 27“ 4K

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.

I use iPad screenshots and videos even in the Desktop section of the forum when I expect no relevant difference.

 

  • 7 months later...
Posted

I ran into a problem that I believe is related.

I start with a live noise filter (100% intensity) and a pixel layer filled with black.
At this point everything is fine.

But after grouping, the composite alpha is also affected by the noise live filter.

ca01.png.103cb266e745bf2a14a42b8b64551209.png

 

If i make the noise live filter as a child, everything goes back to normal and the composite alpha is no longer affected.

ca02.png.70ee1c85d516648fb8a732c8edc493f8.png

Posted
1 hour ago, Lisbon said:

I ran into a problem that I believe is related.

I start with a live noise filter (100% intensity) and a pixel layer filled with black.
At this point everything is fine.

But after grouping, the composite alpha is also affected by the noise live filter.

ca01.png.103cb266e745bf2a14a42b8b64551209.png

 

If i make the noise live filter as a child, everything goes back to normal and the composite alpha is no longer affected.

ca02.png.70ee1c85d516648fb8a732c8edc493f8.png

This is kind of consequent by Affinity:

  • Filters nested affect RGB (or CMYK / G) layers only, but exclude alpga
  • Filters at masking position affect RGB and A channel.
  • For noise, this does not make sense. 

The best solution would be Affinity allows to select for every live filter which channel gets affected (independent from nested / masking position), similar to channels panel for destructive filters.

Affecting alpha channels does not do any harm (or is even intended) in case of blur filters, but it is 99% unwanted for noise filters.

Oversight in design of filters. Maybe by design, but non reasonable design.

Mac mini M1 A2348 | MBP M3 

Windows 11 - AMD Ryzen 9 5900x - 32 GB RAM - Nvidia GTX 1080

LG34WK950U-W, calibrated to DCI-P3 with LG Calibration Studio / Spider 5 | Dell 27“ 4K

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.

I use iPad screenshots and videos even in the Desktop section of the forum when I expect no relevant difference.

 

  • 1 year later...
Posted

bump. still unsolved in V2.2

 

Mac mini M1 A2348 | MBP M3 

Windows 11 - AMD Ryzen 9 5900x - 32 GB RAM - Nvidia GTX 1080

LG34WK950U-W, calibrated to DCI-P3 with LG Calibration Studio / Spider 5 | Dell 27“ 4K

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.

I use iPad screenshots and videos even in the Desktop section of the forum when I expect no relevant difference.

 

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