If you choose a colormap for imwrite, how does the colorscaling work? is there a way to try manipulate the caxis by choosing the number of steps in the colormap for example?
The documentation indicates,
imwrite(X,map,filename,fmt) writes the indexed image in X and its associated colormap map to filename in the format specified by fmt.
The question of color scaling is thus irrelevant, as indexed images do not use color scaling.
I suspect you might want to take advantage of the File Exchange contribution "freezeColors" to convert the image into a truecolor image that you can get() the Cdata property of and imwrite() that array (with no map)