How to turn image into black and green scale?

[mistyfalls236]

How do you make a picture into black and green scale? Kinda like the grayscale or black and white scale.

[chaarmann]

Classical grayscale is easy: just make every second black dot white.
Black and white scale: use brightness value of each pixel and redraw it with color white with the corresponding brightness.
Black and green scale: like black and white scale, but use green instead of white.

[mistyfalls236]

I was able to successfully make a grayscale and black and white. But I could not figure what values to put for black and green scale. I know red and blue are zeroes. But my final result always seem to be just green and no black.

[chaarmann]

It was all green?
I know that problem too well from a game I played on C64 25 years ago. There was a blue river with red piranhas inside. But I had a black-and-white monitor and they used the same brightness for red and blue. So I always got eaten by the invisible piranhas and never made it on the other side of the river. During that time I played all games up to the end and was very proud of it. So I spent hours for hours to blindly avoid the piranhas, and it nearly drove me mad. I still couldn't do it. I was cursing, why could'nt the programmer just use different brightness? So I started hacking the game to change the brightness of the piranhas to be able to cross the river. My programming career began ...