Blur Image Background in Affinity Photo
While the ultimate goal is to blur the background of an image, I also want to save the outline that I’ve drawn around the main object in case I want to alter it later or just have it handy for future use.
1. Selection Brush Tool: draw marching ants around main subject
- Mode: Add (toggled between Add and Subtract if the selection got in or out of the target outline)
- Width: (large to begin with, then used smaller brush sizes to accommodate finer details)
- Snap to edges: On
- Soft edges: on (might leave this setting un-ticked next time)
2. Save selection: Select > Save Selection > As Spare Channel
3. Save file (marching ants selection has now been saved as a Spare Channel in the Channels Panel
4. To add Gaussian Blur to background we’ll first load the pixel selection from the shape previously saved to the Spare Channel:
- In the Channels panel press ^(ctrl)-click in the tiny gap between the thumbnail of your shape and the Spare Channel text, then
- Select Load to Pixel Selection in the pop-up dialog window
- Source: Affinity Help “Pixel selections from channels” > Section titled “To create a pixel selection from a channel”)
5. Then Invert pixel selection (so the marching ants are around the background and not the main subject): Select > Invert Pixel Selection
6. And finally add Gaussian Blur via a Live Filter Layer: Layer > New Live Filter Layer > Blur > Gaussian Blur…
- Preserve Alpha: On
- Radius: 26px
- Opacity: 100%
- Blend Mode: Normal
- Then exit dialog window by ticking the red dot in upper-left corner of dialog window
7. Save file
