Thank you for your email.
The error is not in the preview JS, but in the defective alpha blending in the image (alpha/RGB + interpolation).macadoum wrote: Sat Dec 13, 2025 5:36 pm ... On the left, the original file on my computer. On the right, after the upload.
The PNG does not have alpha=0 everywhere in the areas that are supposed to be "transparent", but rather a large number of pixels with very small, but ≠0 alpha (e.g., 2–6) and ‘garbage’ RGB values. During normal browser rendering, these RGB values are slightly offset against the background -> this looks like "scanlines".
If you open the image in a separate browser tab or Gimp, the messed-up transparent area is also displayed as "scanlines".
Therefore, no correction is necessary in the preview JS.
Best regards and have a relaxing Sunday,
Frank
