I haven't figured out how to control both values, but I found out how to turn the contrast up fully, and edit the brightness. woohoo. Feel free to look inside to change the costume to anything you want.
If I had to guess how this works, I would say it like this: Basically, a computer can only display 256 values for red, green, and blue light individually. When you turn the ghost effect up to 99, it forces the computer to render the image with the few colors it has left. if you add 255 to all the values, they can only display brightnesses between 255 and 256, which ends up being very very desaturated versions of red, yellow, green, cyan, blue, and magenta. By stamping the costume like 200 times, I'm layering those solid colors on top of eachother, adding saturation and opacity over and over until they become relatively visible. Due to some bugs with scratch's engine, it's impossible to get back to 100% opacity, but I got pretty close. I noticed that as the value increases, it cycles between all the brightness values, before going to the next contrast level. that's why the slider has such a tiny range.
