Thank you @joa-quim for the solution.
I had already tried to use color=“gray”, but got an error. Turns out there seems to be an error in my combination of Atom/Juno/Julia 1.0, because once I use the command in a fresh instance, it works. However, if I want to change the color, I get an error. As I had started from color=“rainbow”, I was not able to change the color-coding.
Thanks for clarifying. I did not know about grids before, because I am coming from a biological/ pharmaceutical field.
I am doing a lot of microscopic imaging, but images are just regarded as a “map of values”, each value representing a photon-count/intensity value (we are using quantitative cameras, monochrome, not RGB). The values are the important part, the color is for display purposes only. Whether I display the image in yellow, red, grey or rainbow is not important, as long as I can read out or access the intensity value.
I frequently use those images, i.e. maps of values, to do some math (e.g. devide one image by another for normalisation or ratio calculation). That’s why I always asked about “images”. As far as I understand it now, my “images” are basically grids that are displayed in greyscale by default.
That explains the problem I observed with the display:
grdimage always assigns RGB to the displayed image. The different shades of gray are encoded in RGB, not in black/white as I expected it. But saving the grid works fine, so this is not really an issue.
I had tried to understand all the different options, but with no background in grids, geological business and the different file formats, I was at a complete loss.