- build-ext-gstate DOC #!optional FILL-ALPHA STROKE-ALPHA BLEND-MODEprocedure
Adds a PDF 1.4 ExtGState resource to DOC and returns it, for controlling alpha transparency and blend mode in later drawing (see set-ext-gstate). FILL-ALPHA and STROKE-ALPHA, if given, are constant alpha values from 0.0 (fully transparent) to 1.0 (fully opaque), applied to fill and stroke operations respectively. BLEND-MODE, if given, is a blend mode name, e.g. "Multiply". Signals an error unless DOC was created with PDF version "1.4" (see build-doc), since ExtGState is a PDF 1.4 feature, not part of core PDF 1.3.