I know this is an old Post but the 2 above this post actually didn't know what his problem was it wasn't the code its his image any image that is transparent or ain't canvas just right will show grey lines its because your image for one is not the size for the game its bigger and, your forcing it a smaller size only solution i can tell you or anyone else that having issues with images with gray lines on the edges is Canvas the transparent image bigger so you wont have them Gray lines when scaling with the image .. If my sentence sucks oh well i tried my best..
Again sorry for bumping an old post..