Spot Colour in Gimp

“Why Gimp?”  I was asked, “It’s so difficult and non-intuitive.”  I think Graham Field in our group answered that question quite well.  “You see I’ve got Adobe Lightroom, but the licence prevents me from putting it on my laptop for use when I’m travelling.  Whereas Gimp is free and I can use it on as many machines as I like.”  It’s not that different to Photoshop and quite easy to use once you learn your way around the program.  It’s worth spending the time to learn a few tricks in Gimp.

Spot Colour Frances

I have not included the instructions to correct perspective in these instructions.  If you want to explore for yourself, there is a simple tool in the tool box that will achieve this quite easily.

Here is the walk through for spot colour.  

1. Open Gimp

Gimp - 6

This is what it looks like, The main window in the middle with tool box on the left and layers / brushes dialog on the right.

2. Open Image


This is easy.  You just drag and drop the image from windows explorer into the main window and it will open.

3. Make selection


I am using the Scissors tool.  By placing dots on the outline, the program will select a path of high contrast between the dots.  If it gets the path wrong, you can click on the line and drag it across to where it should be.  Close the object by clicking on the first dot.  You can still edit the shape until you convert it to a selection by hitting the enter key.


The selection is now surrounded by marching ants.

At this point we will invert the selection, so that we have selected the background and not Frances.  From the select menu click “invert”

4. Duplicate Layer

Image menu – “duplicate”.  Alternatively right click the layer icon in the layers box and select “duplicate layer”.

5. Create mask from selection

Layer menu – “Mask” – “Add Layer mask”.  Alternatively right click the upper layer icon in the layers box and select “Add Layer mask”.

A dialog will appear from which you choose “selection” and click “Add”.  You will notice that a little mask icon will appear next to the layer icon in the layers box.  Note that the active item (layer or mask) will be surrounded by a white frame.

At this point we want to clear the selection.  From the “Select” menu choose “None”.  The marching ants should disappear.

6. Desaturate top layer


First make sure the white frame (indicating the active element) is on the upper layer – on the picture icon, (not the mask) by clicking on this icon.

Now from the Colour menu click on the – “desaturate” command.  You will find you have three options, Lightness, Luminosity, Average.  Try all three and select your favourite.  We should now have the spot colour image that we anticipated.  If not, go back over the steps to make sure you haven’t made a mistake.

7. Export as .jpg


An annoying feature of Gimp is that the only “save as” option is the Gimp native file type, .xcf.  To save the image as a .jpg, (or any other file type) you must use the “export as” command (from the “File” menu).  Just follow the steps to save the image at the highest quality setting.  Make sure you use a different name to the original image to prevent overwriting and losing the original file.