Comment 75 for bug 482993

Nathan Orloffmo wrote
> Even simple things like changing an image to grayscale.

Are you trying to change an embedded or linked bitmap? Then of course 'Extensions > Color > Grayscale' doesn't do anything: the extension modifies the style attributes of vector objects and has no effect on bitmap images. For bitmap (aka raster) graphics (linked or embedded), you could 'Filters > Color > Desaturate' or maybe one of the raster extensions (Extensions > Raster), though I don't know at the moment which one of those would allow to convert the image to grayscale or desaturate it.