As i understand currently only File Input node have option to automatically convert bitmap to heighfield - i dont know why this alghorithm not available as separate node, so i may sugest to add it
here i have color node that generates same image as heightmap, but i can not work with it due to there no bridge to convert bitmap into heightmap or so
I know that i can just use primary image, and not image that color node gives me - but i have some ideas about using specificly image generated by color node with filters nodes that process bitmap datatype to create interesting landscape solutions