Keep transparent edges transparent.

Try a transparent sample

Save our 101 × 103 transparent PNG. It contains a fully transparent border, an opaque coral center, and a half-transparent coral strip. Open it in the image splitter and choose 3 rows and 4 columns.

Export as PNG first. Open an edge tile over a contrasting background in an image editor: the outer border should let the background show through, and the half-transparent strip should blend with it. A checkerboard in a preview is a display aid; it is not part of the downloaded image.

PNG and JPEG give different results

JPEG cannot store transparent pixels. Before encoding it, PicMason paints the selected background behind the image. With a white background, the sample’s half-transparent coral (RGB 240, 96, 72; alpha 128 of 255) blends to approximately RGB 247, 175, 163 before JPEG compression. The final JPEG can differ slightly because its encoding is lossy.

Export a deliberate background

1. Select JPEG in the output settings.
2. Choose a background color that matches where the tiles will be used.
3. Set the JPEG quality, then generate a fresh export.
4. Open an edge tile and check it against the intended page or design background.

The quality control affects JPEG compression. It cannot restore transparency, fix an unwanted background, or recover detail already absent from the source. Choose PNG if the background may change later.

When to use WebP

WebP is another export option when you need transparency and the destination app accepts WebP. Its adjustable quality uses lossy compression, so colors can differ from the decoded source. It does not use the JPEG background color. Choose PNG when avoiding another lossy encoding step matters more than the output format.

If an edge looks black

First check the downloaded format. A transparent PNG or WebP may look black in a viewer that uses black behind transparency. Place it over white to see whether the border is actually transparent. For JPEG, confirm the selected background color and export again if needed.

Dark pixels baked into the source are real image content. Splitting does not remove backgrounds or repair a pre-existing dark halo. The tool also rejects animated files rather than silently exporting only one frame.

Transparent colors pass through the browser’s image decoder and canvas. The guarantee here is retaining usable alpha in PNG output; it is not preserving hidden RGB values beneath fully transparent pixels or the source file’s metadata.