Encode PNG to Look Correct Only on a Chosen Background

1) Upload intended final appearance (image)

This is the image as you want it to appear after compositing on the chosen background.

2) Choose target background color

Hex: #ffffff

Or upload a flat color swatch image (solid color only):

3) Transparency (alpha)

Use a larger alpha (more opaque) to reduce clamping artifacts.

Comparison background color

Hex: #2b2b2b