photo 2 flood select high cpu usage when changing tolerance

[issicus]

I'm working on a black and white 10k px x 7.5k px png.  When I click and hold with flood select to change tolerance on the fly I am getting 100% cpu usage. Is this to be expected?  I feel like it should be able to handle this. 

I'm running win11 , i5-11600, 16gb ram, rx 6800 xt.   affinity photo 2 ver 2.6.2.

[GarryP]

The Flood Select Tool (amongst others) uses as much of your CPU (as many processing cores) as it can to do what it does as quickly as it can so that the software is as responsive as it can be when doing intensive work (such as, for example, selecting and deselecting millions(?) of pixels in ‘real time’).

It might be more of a concern if it didn’t, because that would mean that the software wasn’t using your CPU effectively.

You might also see that your GPU gets used quite a bit when you have a pixel selection active, and that is because the ‘marching ants’ are ‘handled’ by the GPU.

Unless the CPU usage is causing you a problem then you probably don’t need to worry about it.

[R C-R]

19 hours ago, issicus said:

I feel like it should be able to handle this. 

Is there any indication besides CPU use that it can't, like lagging responses to user input or whatever?

[issicus]

On 4/30/2025 at 7:07 AM, R C-R said:

Is there any indication besides CPU use that it can't, like lagging responses to user input or whatever?

Yes. It is very slow.   

I guess I'm just hoping the devs see this and make it so it doesn't recalculate the selection when I'm switching tolerance (and nothing else). 

[R C-R]

11 minutes ago, issicus said:

Yes. It is very slow.   

I guess I'm just hoping the devs see this and make it so it doesn't recalculate the selection when I'm switching tolerance (and nothing else). 

Can you provide a sample Affinity document that demonstrates this? I ask because on my Mac there is no decidable delay while dragging the Flood Select tool across the canvas to change the tolerance on the fly, even with quite large raster images.

[GarryP]

9 hours ago, issicus said:

I guess I'm just hoping the devs see this and make it so it doesn't recalculate the selection when I'm switching tolerance (and nothing else).

The tolerance tells the software which pixels to select.

Why would you not want the software to recalculate the pixel selection when you change the tolerance?

Or, to put that another way, if you don’t want to select different pixels, why are you changing the tolerance?