Seamless pattern guide
Can a seamless PNG use transparency without visible seams?
Yes. Transparent repeats work when both color and alpha agree across opposite edges and semi-transparent pixels are tested on multiple backgrounds.
Alpha is part of the edge match
A transparent PNG stores color channels and an alpha channel. Two edge pixels may appear invisible on white yet contain different hidden colors or alpha values. When repeated over a dark or saturated background, those differences can form a halo. Seam testing must therefore include alpha as well as visible RGB.
Keep crossing motifs on wrapped copies exactly as you would for opaque artwork. Erasing the right edge and independently erasing the left usually produces different feathering. Duplicate the same pixels or vector object across the boundary, then export the complete tile once.
Watch for matte and premultiplication artifacts
Some applications store semi-transparent pixels whose RGB was blended with a white or black matte. Other pipelines premultiply RGB by alpha and later unpremultiply it with rounding. Either behavior can create bright or dark fringes around repeated motifs. Export without a matte when the destination supports straight transparency.
Do not judge transparency over the checkerboard alone. Place the tile over white, black, mid-gray, and at least one strong color. Examine soft shadows and antialiased lines where copies meet. If a halo changes with the background, inspect the hidden RGB values in the transparent fringe.
Deliver a predictable transparent repeat
Use PNG when the destination accepts it and movable background color is genuinely needed. Preserve the exact canvas size, include an embedded color profile when appropriate, and avoid optimizers that crop transparent borders automatically. Trimming changes the repeat dimensions even if no visible object appears in the removed area.
Test the exported PNG rather than the layered source. Repeat it on whole-pixel coordinates and verify all backgrounds. If a platform converts uploads to JPEG, transparency will be flattened; choose the intended background before upload or supply an opaque version as a separate asset.
