Color can make or break an image, which makes color control an important tool in any image editor’s toolkit. GIMP has some excellent color adjustment tools which can make removing colors easy – more tools than you’ll probably ever need to use!
The general process for removing a single color in GIMP is simple: use a selection tool to select the color you want to remove, and then decide what you want to do with it. You can desaturate it, adjust the hue, or delete the pixels entirely and leave a transparent background, depending on the final result you want.
Usually, in these guides, I give advanced readers a quick version of the tutorial to help speed their project along and then go into more detail later for those who want it. I’ll do the same here, but I’ll also include an extra advanced method at the end for more unique color removal situations.
Also, thanks to Rich Smith for his free photo of the signage that I found on Unsplash for this tutorial!
The Quickest Way to Remove a Color in GIMP
This ultra-fast method works well when you need to remove a solid background color, such as the background behind a logo or a product image on a white background.
- Step 1: Open the Layers menu, select Transparency, and click Add Alpha Channel.
- Step 2: Switch to the Fuzzy Select tool and click on the color you want to remove, creating a selection around it.
- Step 3: Press the Delete key or open the Edit menu and select Clear.
That’s how to remove color in GIMP – or at least, one of the easiest ways. There are a bunch more options that you might need, depending on your image. So if this guide is a bit too brief, or you’ve got a more complex image, read on to learn some other ways to remove color in GIMP.
The Full Guide to Removing Color in GIMP
Step 1: The Alpha Channel
This step is only necessary if you want to actually remove pixels from your image and leave a transparent section. In order to support transparency, GIMP needs an alpha channel to keep track of which pixels are transparent and which ones are opaque. Fortunately, it’s easy!
Open the Layers menu, select the Transparency submenu, and click Add Alpha Channel.
That’s all there is to it! Now you’ll be able to remove color and leave only transparent pixels behind. If you try to remove your selected pixels without the step, you’ll just wind up filling your selection with your current background color.
Step 2: Selecting Your Color
In order to remove color in GIMP, you’ll have to actually tell it which color you want to remove. The selection method you use will depend on the kind of image that you’re working on, and where the color you want to remove is located.
The Fuzzy Select tool is the simplest automatic selection tool for this kind of work. The most important setting it has is the Threshold setting, which determines the color range of pixels that will be selected. Fuzzy Select will select all the pixels within the specified threshold that are directly connected to the first pixel you click on.
This might not make sense at first, so take a look at the examples below.
This photo of a sign for the Bond Street underground station in London looks like it has fairly straightforward colors: gray, white, navy, and red. I want to select the gray background and remove it, but there’s actually a fairly big numerical difference between the grey at the bottom right and the grey at the top left.
Each color on a computer screen has a numerical value from 0-255 for each of the three color channels – Red, Green, and Blue. Since my threshold is set to 20, any pixel with a numerical value within 20 of the place I clicked will get selected. In this case, the threshold is too low, and Fuzzy select has only selected the lower, darker gray area.
If I increase the threshold setting to 45, the range is large enough to encompass the slight brightness change from the bottom of the image to the top. It’s also not so wide that any of the red or navy pixels get selected.
Fuzzy Select will only select contiguous pixels – pixels that are connected in a direct chain from one to the next. To select the two halves of the red circle, you have to combine multiple selections. To select all the characters that spell “Bond Street”, you’ll have to add each character individually since they’re also separated by the navy background.
In order to add new areas to your selection, hold down the Shift key while clicking the next spot on your image. You can also remove areas from your current selection by holding the Ctrl key. If you look closely, you’ll see the cursor displays a small + or – sign to indicate whether you’re adding or subtracting from your current selection.
Step 3: Removal Time
At last, with your color completely selected, it’s time to delete the pixels! If you’re using a PC, you can just press the Delete key, but Mac users may find this doesn’t work depending on which keyboard they use. I only have one iMac keyboard and it’s not even from Apple, so I can’t test this myself – let us know in the comments if it works for you.
No matter what you’re using, you can always open the Edit menu and choose Clear. Assuming you’ve added your alpha channel, the pixels should be replaced by the checkerboard pattern used to indicate transparency (shown above). If the selection gets filled with a color instead, go back to Step 1 and try adding your alpha channel again.
Advanced Method: Remove A Color Without Deleting it
It’s possible to remove color in GIMP without leaving a big transparent hole in your image, and it can be a bit simpler than the whole complex selection process. There are also several ways to go about it, but for the purposes of this guide, I’ll show you the easiest method using the same image.
Step 1: Determine the Color Range
Since we’re not going to be using a selection tool in this method, we don’t have to worry about how to select each individual section of the circle.
Instead, open the Colors menu and select Hue/Saturation.
I think I’ll shake things up by turning the classic red into an eye-watering green for extra attention. Because I already know that the red color I want to remove will fall into the red area of the color wheel, I’ll need to adjust the R section of the image.
While it’s easy enough to figure out the correct color range to edit in this example, it’s not always so obvious. You may find yourself editing the Cyan section instead of Green, or Magenta instead of Red.
If your image doesn’t have such simple colors, you may want to adjust the Overlap slider to also include pixels that are close to red in your adjustment range.
If you can’t seem to locate it, experiment a bit by cycling through the primary color options and pushing the Hue and Lightness sliders to extreme values, just so that you can identify the affected pixels.
But as I said, in this example, it’s easy to know where to start, so I’ll click on the “R” label to select the color for adjustment.
Step 2: Hue Adjustment
Now comes the fun part. Start adjusting the Hue slider, and you’ll see the colors adjust in real-time in the main image window as long as you’ve got the Preview box checked. You can also turn on Split Preview to show the unedited image next to the results of your adjustments.
You’ll also see that the Red in the R section has been updated to reflect the new hue change. In this case, I don’t think the final result is a success, exactly, but it certainly has removed the color red from the image.
I regret my choices! Instead of unleashing this monstrosity on the world, it would be better to just desaturate the red until it’s gone.
You can adjust the Saturation slider to 0 to completely remove all hue from the selected areas – and also to save your eyes.
A Final Word
As you can see from that last example, the ability to remove colors in GIMP isn’t limited to simply deleting pixels. You can remove color by changing it to something else if you’d like, or simply desaturating it until it’s an inoffensive gray tone with no hue at all.
Whatever you choose to do, be sure to use your editing powers for good the next time you remove color in GIMP!About Thomas Boldt