@Frances,

I can see the first three as players in a production environment, Frances, but I can tell you right now that creating a feature that auto-converts a colour image to greyscale in a way that is pleasing and accurate to the human eye isn't going to happen real soon!

Even the Great and Almighty Adobe Systems gives the user options on how the saturation and brightness of every hue in a photo should be weighted to take into account the reality that colors doesn't naturally port to brightness (greyscale) values, partially because black and white is a man-made, artificial colour "state". Photoshop's Black & White Adjustment lets the user decide how "heavy" or light the hue contribution winds up in a greyscale equivalent. Here's a colour image, and then a straight greyscale by removing any saturation, and at bottom is an adjusted greyscale using the Photoshop feature.

Click image for larger version. 

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It sounds like an operation, that to satisfy artists and their clients, is one best done manually.

-g