Re: Preventing -extent from converting to RGB

----- Toby Thain <[email protected]> wrote:
> On 2016-08-27 9:36 PM, [email protected] wrote:
> >
> > ----- Toby Thain <[email protected]> wrote:
> >> Hi,
> >>
> >> I have a grey scale source image and I am applying a -rotate and an
> >> -extent operation. I'm finding that the output is RGB, presumably
> >> because of the background colour? Is there any way of getting the
> >> equivalent of -extent without the RGB conversion? (I know I can add a
> >> -channel to go back to greyscale, but it seems superfluous.)
> >
> > Did you try making the background a grayscale colour?
> 
> That was my first thought too, but the doc only talks about RGB colours; 
> there was no obvious way to specify a single channel "colour." (Of 
> course there may be a way I missed.)

Try "-background white", "-background black", "-background '#a0a0a0'",
etc.  As long as all three components of the background color are
equal, it won't force GM to write an RGB image.

BTW I'm assuming you are writing a PNG, and working with the current
version of GM.

Glenn

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