Corrigendum to "Random grid-based visual secret sharing with abilities of OR and XOR decryptions"[Journal of Visual Communication and Image Representation. 24(2013) 48-62]

It has been observed that the contrast values for (2, 3) VSS scheme, (2, 4) VSS scheme, (3, 5) VSS scheme and (4, 5) VSS scheme claimed by Wu and Sun (2013) are found to be incorrect. Since the same values are cited and compared by many other researchers in their works, we have calculated and presented the correct values of contrast in this note.