Background Erase

[Sydlyne]

I have an issue with Affinity Paint2 on PC.

I will be flood erasing at 40% on a complex (windmill) image with lots of enclosed sections to erase the white background.

After 10 or so blocks it stops flood erasing blocks and will only erase some pixels

I switch away to Paintbrush, then come back to Flood Erase and it has reset to 1% instead of the 40% I had. I reset to 40% and continue for another few blocks till it happens again.

I have to do this swap backwards and forwards dozens of times to get my image onto a transparent background.

[NotMyFault]

The background erase brush samples the color of the background at the starting position of every brush stroke, and uses the sampled color to distinguish between background and foreground pixels. If you by chance start in an area already erased, it can confuse the algorithm, as the remaining not fully erased pixels may have a color deviating too much. 
 

I get best results if using a real large brush and remove all background in one single stroke, covering the overall image.

never the less, the tool fails to remove color contamination at edges, where background and foreground are mixed.
 

The tool works great in some situations, but has its limits.

Can you upload the actual image? We may find a good way to remove all background.

[Sydlyne]

This is one of my images, I have a lot of these to make transparent. I've been using the Background Fill, then the Brush for the detail.

[NotMyFault]

Thanks for the image.

There is no easy solution:

• some white areas are not fully white
• not all fully white areas are background

It could be faster to use different approaches:

1. use a non-destructive workflow. This allows to correct small mistakes any time later without using undo
2. use flood selection tool, and deactivate continuous, activate antialiasing. Then click on a pure white area. Try to reduce threshold a tiny bit below the default 20%
3. create a new mask from selection by clicking the masking icon.
4. deactivate selection
5. invert the mask
6. add a fill layer below in blue (or other strong color)
7. there are a few spots inside the later needing correction of the mask layer.
8. use pixel brush, set hardness to 80%, size as required e.g. 8-32px
9. paint in white over areas with missing pixels.
10. Paint in black over areas who belong to background.
11. when all is corrected, merge visible or export as png.

[Sydlyne]

OK, great!  That gives me something to try!

 

Thanks

[knoefix]

Hello.

I had the same effect.
The following worked for me:
I hold the mouse button and paint over all areas.
When the effect appeared, I restarted in the pixel-free space and was able to continue painting.
It seemed to me that there is a time lag. If I paint quickly, the result will appear more often.

My settings in the picture.