[sf-lug] Forcing a greyscape JPEG into RGB colorspace?

Bill Kendrick nbs at sonic.net
Mon Jun 14 10:30:29 PDT 2010

So I've got a system that receives images from users
We then ship those out to a 3rd party.  This 3rd party
requires that they be JPEGs (easy to convert to) of a
certain size (easy to check) and in RGB colorspace
(vs CMYK or Grey).

I had a great bit of difficulty, and simply threw my hands up,
when trying to "encourage" a greyscale image (that is, a picture
that's only grey pixels) to become an RGB colorspace JPEG.

Every automated tool I tried (libjpeg-progs, ImageMagick,
possibly others; it's been a while) seemed to ignore my colorspace
hint, and said to themselves "ah, but it's only grey pixels;
let's just save it as Grey colorspace!)

Does anyone here have any suggestions on a tool that can handle
this for me?  (Again, this will be running on a server as part
of an automated process, so desktop apps are out; don't bother
suggesting The GIMP :) )

I'd be willing to whip something up in C that used libjpeg
and ran on our server to handle the 'force-to-RGB-colorspace'
task.  (The other idea I had was to introduce an off-grey pixel
into the source image, to "convince" the tools we're using now
that the image really does deserve RGB colorspace :) )

Thanks in advance,


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