Not in black or white, encryption of grayscale images by donor–acceptor Stenhouse adducts.

Invisible inks have been applied for the secrecy of texts, symbols and binary images. Based on the photochromism of donor–acceptor Stenhouse adducts (DASAs) in the solid-state promoted by ester-containing molecules, we report the encryption of grayscale information by controlling the kinetics of photoisomerization. [ABSTRACT FROM AUTHOR]