What is Alpha channel?
Also known as: Transparency
An additional per-pixel data channel storing transparency information. Alongside RGB color channels, alpha enables compositing, background removal, and masking.
In detail
An alpha channel is a fourth channel (alongside R, G, B) storing per-pixel transparency from 0 (fully transparent) to 255 (fully opaque). PNG and TIFF support alpha; JPEG does not (JPEG's lack of alpha is its main limitation for textile work). In textile design, alpha is used in: background removal (the subject has alpha 255, the background has alpha 0); layering (an embroidery motif on top of a printed background with smooth feather alpha at the edges); compositing (combining an AI-generated subject onto a hand-painted background); cutting masks (defining where embroidery stitches should and should not be placed). AI background removal models output an alpha channel as their primary deliverable. Print-ready files for digital printing typically have alpha set to 255 everywhere (the printer ignores alpha during printing) but rendered previews use alpha for client review.
Example
A BRIA RMBG 2.0 model removes the background from a product photo. Output: the subject (a folded scarf) with alpha 255, the surrounding background with alpha 0, soft alpha gradients at hair-level edges where the model is uncertain. The result drops cleanly onto any new background.