Flood selection tolerance not working with alpha

[Michael Walter]

Why is it, that the flood selection tool tolerance is not working without a background pixel layer (see video) ? Is it because this tool doesn't consider alpha but only RGB? (Photoshop f.e. does).

Am I missing something here?

Michael  

[Dan C]

Hi @Michael Walter,

Welcome to the Affinity Forums

On 8/3/2021 at 10:51 AM, Michael Walter said:

Why is it, that the flood selection tool tolerance is not working without a background pixel layer (see video) ? Is it because this tool doesn't consider alpha but only RGB?

I can confirm that Affinity Photos' Flood Selection tool creates selections based on RGB values only, not RGBA values - hence the behaviour you're seeing.

Once you enable the bottom layer, it is composited into your document and therefore the colour values on your canvas change, as does the behaviour of this tool.

I hope this clears things up!

[Michael Walter]

Hi @Dan C,

thank you for your answer, so I didn't overlook anything or use the tool incorrectly. - Do you have any idea what might have been the advantage from the point of view of the affinity developers of not taking the alpha values into account when selecting? Or is this topic perhaps worth a suggestion for improvement?

[Dan C]

On 8/5/2021 at 1:39 PM, Michael Walter said:

Do you have any idea what might have been the advantage from the point of view of the affinity developers of not taking the alpha values into account when selecting? 

Unfortunately I'm not technically versed enough to provide reasoning or advantages here, I've simply been informed this is how the Affinity app calculates flood selections - my apologies!

On 8/5/2021 at 1:39 PM, Michael Walter said:

Or is this topic perhaps worth a suggestion for improvement?

I'll move this thread to the feedback section of the Forums for our devs to see and consider for you now

[Wosven]

Yes, this problem was already mentioned, and since it's not always a solution to add a background colour just to try selecting the part we want, adding definitly or as an option the transparency would be important.

[plyoung]

Seems like such a simple thing to have for the Flood Select tool. Used it a lot in other tools I used before to cleanup images during game development. PaintShopPro even have an option to choose if you want to select based on alpha or colour. Now the workflow is slowed down by having to create a background layer or messing with a combination of flood and selection brush to do what should just be a slider and click away. Affinity has so many cool features but also miss some usability stuff sometimes.

[edit] I see this forum category related to v1, but this is missing in v2 too. ... shrug