Was this samurai the inspiration for the blind general's character in One Piece?
The blind samurai you're referring to is Zatoichi, and the blind Admiral in One Piece is named Issho, aka Fujitora. And yes, as revealed in SBS Volume 74, Fujitora was inspired by Zatoichi, and particularly his portrayal by Japanese actor Shintaro Katsu. Both swordsmen share quite a few characteristics, such as their blindness, proficiency with a sword, or their love of gambling.