Problem
Premultiplied-alpha edges create dark fringes around transparent graphic elements.
Solution
Root Cause / Diagnostic:
Assets exported with premultiplied alpha have their semi-transparent edge RGB values pre-blended with black. When placed over bright thumbnail backgrounds, these edge pixels retain a dark, dirty fringe that looks unpolished and harsh.
Actionable Fix:
1. Use Photoshop's Layer > Matting > Defringe (1–2 px) or Layer > Matting > Remove Black Matte to strip premultiplied black fringe values.
2. Export transparent overlays as straight (non-premultiplied) alpha PNG-24 assets.
3. Place the graphic over a solid white test background to verify edges are razor-sharp without dark halo outlines.
Pro Tip:
Apply "Remove Black Matte" to 3D renders and graphic assets before compositing; stripping premultiplied alpha fringes guarantees clean edges over bright backgrounds.
Assets exported with premultiplied alpha have their semi-transparent edge RGB values pre-blended with black. When placed over bright thumbnail backgrounds, these edge pixels retain a dark, dirty fringe that looks unpolished and harsh.
Actionable Fix:
1. Use Photoshop's Layer > Matting > Defringe (1–2 px) or Layer > Matting > Remove Black Matte to strip premultiplied black fringe values.
2. Export transparent overlays as straight (non-premultiplied) alpha PNG-24 assets.
3. Place the graphic over a solid white test background to verify edges are razor-sharp without dark halo outlines.
Pro Tip:
Apply "Remove Black Matte" to 3D renders and graphic assets before compositing; stripping premultiplied alpha fringes guarantees clean edges over bright backgrounds.