I am trying to make the background of a drawing transparent, yet the drawing is a little bit blurry giving some problems. The drawing is only black and white, and I am trying to get all the white removed. I believe the best way is to get each pixel to be black, yet having the opacity be such that when placed in front of a white background, it looks just like the original drawing. This should achieve how the drawing would have looked like if he had drawn with a clear background in the first place (yet his drawing program doesn't have clear backgrounds, which is why he asked me cuz I have photoshop, and I thought it'd be easier than I thought).
I tried to use the magic eraser and select color range (where the color was white) and neither gave me what I want. They both treat the grey from the blurriness as a grey and only sometimes simply erasing it.