Non colour output

Software GIMP
1

Hi,

When I use Image → Mode → Grayscale and then send the resulting image to my professional print partner (who will charge me less for a non colour print) the printer software they are using still recognises it as a colour image.

I managed to overcome this by using Imagemagick to convert the pdf output I got from GIMP (using the Imagemagick command -colorspace gray -type grayscalealpha) to produce a new pdf that the printer’s software then recognised as non colour.

Unfortunately text that I had written in a large font was visibly undefined in the resulting print I got back. When I went back to the files I sent to the printer and zoomed in sufficiently I could see that in the conversion process the font had become less defined, so although the Imagemagick conversion is getting round the colour issue it is causing an unacceptable quality output.

If I had been able to send the printer the output straight from GIMP I’m sure I would have been happy with the definition, if only I could produce the output in such a way that the printer software would recognise it as non colour.

Can anyone propose a different solution that is available natively out of GIMP that will achieve the same outcome as what I get when I convert using the above commands in ImageMagick?

I verify the output using exiftool, the difference in a file the professional printer’s software likes appears to be that it comes with the tag:

  • EmbeddedImageColorSpace : DeviceGray

Thanks in advance for any suggestions you are able to provide.

2

Welcome to the forum!

Just looked, GIMP in PNG export will give you in the options dialog a “pixelformat” drop-down where you can select “8bpc GRAY”. That’ll do it.

Didn’t see a similar option for .pdf, .jpeg, or .tif…

3

ImageMagick is a raster image processor. So any vector elements in its input PDF, such as text, will be rasterized (converted to pixels).

IM isn’t a useful editor for PDFs that contain vector elements that you want to retain as vector. Other tools, such as exiftool or qdf, may be more useful.