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.
How does an alpha channel store transparency?
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.
When does an alpha channel matter in a print file?
An alpha-matting 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.