As a self-taught beginner artist, this tool is super handy! It saves me a significant amount of prep time otherwise spent using photo editors to generate the different values. Thank you!! My only suggestion would be to implement an optional grid overlay.
Great product. The missing piece in learning painting. It's true that many artists turn photo to greyscale to study tonal values. Also, many artists take a photo of their painting and turn it to greyscale also to compare with the reference.