Spec
Alpha Channel
The transparency channel in a raster image that controls which pixels print and which stay clear.
Definition
Alpha channel is the transparency channel in a raster image. It stores a value from 0 to 255 for each pixel that defines how opaque or transparent that pixel is. A fully transparent alpha pixel does not print. A fully opaque alpha pixel prints at the assigned color. Alpha values between the two extremes are partially transparent and rasterize into a soft edge in production. PNG and TIFF file formats support alpha. JPG does not, which is why JPG is not the preferred format for transfer artwork. The DTF production engine reads alpha to decide where the white underbase prints and where the film stays clear.
Related Terms
Transparent PNG
A PNG file with a transparent alpha background so only the design prints and the surrounding film stays clear.
White Underbase
A layer of white ink printed beneath color ink so the design reads correctly on dark or colored fabric.
Knockout
An area of a design where the white underbase is removed so the substrate color shows through the print.
Print-Ready File
An artwork file that meets all the technical specifications required to send directly to the production press.