SaveForWeb: Resizing in SFW adds white border pixels on transparent edges

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  • Problem
  • Updated 6 years ago
  • (Edited)
If you take a transparent image and scale it down in Save-for-Web, it adds white pixels around the edges that should not be there, and that get sampled into the borders of your transparent image when scaling. This does not happen if you resize before and then go to Save-for-Web. I know why this happens: Photoshop has 2 kinds of transparency: A 1-bit stencil transparency (go over an antialiased edge with the color picker, it will show all pixels' colors ignoring the transparency, and nothing where the 1-bit transparency is!) and the regular Alpha value of any given pixel. When going to Save-for-web, Photoshop fills the 1-bit stencil mask with white and hands over the RGBA data to SFW - and when that gets scaled down, the white pixels start to bleed in!

If you don't scale the image, there's no difference between filling the 1-bit stencil mask with white or not (cause it's always 100% transparent anyway!). It only shows when scaling...
Photo of Peter Schwarz

Peter Schwarz

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  • slightly puzzled nobody has noticed that before

Posted 6 years ago

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