Average colour GIMP 3 plug-in: effortless instant results

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What does t’his average colour GIMP 3 plug-in do?

This one-click plug-in calculates the average colour of an image, then fills a new layer with that colour. It handles any colour or greyscale image and generates the exact same average colour as Photoshop’s Average blur. (The plug-in works only in GIMP 3, not GIMP 2.)

To use it, choose “Average colour” from the GIMP Colors menu. That will generate a new layer in your image filled with its average colour. Note that it calculates the average colour based on a copy of the currently visible layers.

I was surprised that this important capability has never been built in to GIMP. When I searched for solutions, I found a wide variety of approaches. But all of them involved programming or multi-step copy/paste user-unfriendly approaches.

Warning: science stuff. The most photographer-oriented approach dates all the way back to 2014. Claudio Bacchiani posted a simple answer to get the mean or average colour in GIMP for an RGB image: take the mean value for each of the red, green, and blue channels in the histogram, then plug them into the foreground/background colour picker. But that requires understanding how different image types calculate those values, and different ways to use math to convert them to values the GIMP colour picker can use., and move them into

So I decided to automate that process. It was essential to make it as straightforward as possible, and work with native GIMP without requiring any additional software.

Then I learned that photographers increasingly work in “linear space”. Average colour for a linear image is quite different than for a RGB image. So I have updated the plug-in to automatically detect whether the current open image is RGB or linear, and generate the appropriate average colour.

What are the advantages of knowing an image’s average colour?

Knowing an image’s average colour helps you:

• Identify colour casts

See warm, cool, or tinted biases affecting your entire image.

• Diagnose tonal balance issues

  average-image-colour-v3.zip

Discover whether your image leans too dark or too light overall.

• Create complementary colour schemes

Generate a starting point for introducing colours that create visual harmony, and film or cinematic looks.

• Create repeatable results

Replicate successful colour grades across different projects.

• Speed up your editing workflow

Make targeted, data-driven adjustments instead of trial-and-error tweaking of curves and colour wheels.

• Build professional split-toning effects

Understand any existing colour bias before strategically applying different tones to highlights and shadows.

• Neutralise white balance problems

Correct lighting colour casts by inverting or subtracting the average colour.

• Make informed creative decisions

Know your baseline colour so you can intentionally enhance or counterbalance it for specific moods.

Why does knowing the average colour of an image help with colour grading?

The average colour reveals your image’s overall colour bias. With that insight, you can make informed decisions about whether to neutralise it or enhance it for creative effect. It’s a colour diagnosis tool that shows you exactly what’s influencing your entire image. By inverting this average colour and blending it back into the image (using blend modes like Subtract or Difference), photographers can neutralise unwanted colour casts and push the image toward a more neutral or intentionally stylised colour palette.

How does average colour help achieve consistency across a photo series?

When editing multiple photos from the same shoot, the average colour acts as a reference point for maintaining visual cohesion. By comparing average colours across images, you can ensure your wedding photos, portrait series, or product shots all share the same mood and colour palette rather than looking disjointed.

What’s the relationship between average colour and complementary colour grading?

Once you know your image’s average colour, you can introduce its complements to create visual tension and interest. This is the foundation of popular cinematic looks like the orange-and-teal aesthetic. Understanding your starting point lets you push colours in intentional, harmonious directions.photographers increasingly work in “linear space”photographers increasingly work in “linear space”

Why is average colour useful for correcting white balance issues?

If your image has an unwanted colour cast (like overly warm indoor lighting or cool shadowy tones), the average colour immediately reveals this bias. By inverting or subtracting the average colour, you can neutralise the cast and restore more accurate, natural-looking tones.

How does average colour help with split-toning techniques?

Split-toning involves applying different colours to highlights and shadows. Knowing your image’s average colour helps you understand which tones are already dominant, allowing you to make strategic choices about employing contrasting colours to shadows or highlights.

Can average colour improve shadow and highlight balance?photographers increasingly work in “linear space”

Absolutely. The average colour shows you whether your image leans too heavily toward dark or light tones. This insight helps you selectively adjust shadows and highlights to create better tonal separation and dimensional depth.

Why do professional colourists care about average colour?

Professional colourists use average colour as a diagnostic tool to quickly assess an image’s colour health. It reveals problems that might not be immediately obvious to the eye, like subtle magenta shifts or green casts. Average colour provides a mathematical starting point for corrections rather than relying purely on subjective judgment.

How does understanding average colour speed up the editing workflow?

Instead of randomly adjusting curves and colour wheels hoping to find the right look, knowing your average colour gives you a precise starting point. You can make targeted adjustments based on actual data, reducing trial-and-error and helping you achieve consistent results faster across multiple images.

What’s the difference between average colour and dominant colour?

Average colour and dominant colour are fundamentally different ways of analysing an image’s colour content.

Average Colour

Average colour is a mathematical calculation. It adds up the colour value of every pixel in your image and then averages them to form one uniform colour. Think of it like mixing all your paint colours together on a palette.

Examples:

Dominant Colour

Dominant colour is the most frequently occurring colour or colour range in your image. It’s what colour actually takes up the most space, regardless of how other colours might mathematically balance it out. The dominant colour is usually what your eye naturally notices first. An image can have multiple dominant colours in different regions.

Example:

In a sunset photo with a small but vibrant orange sun against a vast purple sky, the dominant colour is purple (it occupies more pixels).

Practical comparison

Imagine a portrait with:

The dominant colour is white: it occupies the most pixels.

The average colour is pale pink: red + white + black all mixed together.

Why This Matters for Photographers

Average colour is better for technical corrections like removing colour casts or creating complementary grading schemes, because it represents the overall colour “weight” of the image.

Dominant colour is better for understanding visual impact, which helps with creative decisions about colour harmony and composition

Both have their place in photo editing: average colour for colour operations, dominant colour for understanding visual hierarchy.

It’s important to understand that while generating an image’s average colour is a pretty simple, straightforward, standardised mathematical process, identifying its dominant colour is not. There are a variety of methods to compute a dominant colour, and they result in different hues. Many online services let you submit an image and get the dominant colour palette back. But you’ll find that they all return different dominant colours and palettes—usually close but never the same.

Here’s an example of the surprising differences between online dominant colour tools. You can see the palettes include different colours.

FreeTool (https://www.freetool.dev/dominant-colors-of-the-image/)

ImageMagixOnline (https://www.imagemagixonline.com/tools/dominant-color-finder)

This side-by-side comparison of the dominant colour chosen by each tool shows the wide variation in how different online services choose a dominant colour:

So you’ll need to experiment to find an online service that suits you personally.

Important things to understand about RGB (gamma encoded) vs Linear light

When you calculate average colour in linear light, it appears lighter than when you compute average colour in RGB.

Why results differ between colour modes and bit depths

Different transfer functions

Colour spaces like sRGB and Adobe RGB apply different transfer functions (gamma curves) than linear-light spaces that encode brightness non-linearly. Gamma-encoded RGB values distribute precision to match human vision sensitivity. But they’re not proportional to linear physical light intensity. So averaging RGB values yields different numeric results than averaging linear light values.

Bit depth effects

Higher bit depths (16-bit, 32-bit) provide greater precision. The numeric average can shift slightly with different bit depths due to rounding. These variations are expected and reflect how the image data is stored.

The new enhancement to the plug-in: linear light support

The new linear-light mode automatically, where values are proportional to actual light. It will generate a floating-point, profile-tagged layer. The plug-in will offer two modes: Linear Light and RGB.y detects whether the image is RGB or linear space. It then computes the average colour appropriately for the colour encoding for the image.

Why RGB averaging works for most users

Standard workflow compatibility

Most photographers, designers, and digital artists work in standard colour spaces (sRGB, Adobe RGB, ProPhoto) throughout their workflow. RGB averaging integrates seamlessly with these workflows and p, where values are proportional to actual light. It will generate a floating-point, profile-tagged layer. The plug-in will offer two modes: Linear Light and RGB.roduces expected results.

Predictable and practical

RGB averaging delivers intuitive results that match how colours appear on screen and align with familiar tools like eyedroppers and colour pickers. This is the practical choice for design work, photo retouching, web graphics, and general photography.

Wide application support

Most imaging applications, plug-ins, and export workflows use these standard color spaces, making RGB averaging the compatible default.

Why linear light support is useful for specific workflows

Specialised high-precision editing

Some photographers work in 16- or 32-bit linear light for specific situations requiring maximum precision: HDR processing, complex compositing, or scientific imaging where maintaining physical light relationships is critical.

Physically accurate blending

Linear light averaging respects how light combines physically: two lights at 50% intensity equal one light at 100% intensity. This matters for certain technical workflows but is usually unnecessary for general photography.

Linear-only workflows

Photographers working in linear-to-output pipelines benefit from maintaining linear light throughout processing.

Summary

The plug-in now provides:

What languages is the plug-in available in?

This average colour plug-in for GIMP 3 is available in the following languages. You don’t have to do anything to see it in your language. GIMP will automatically load the correct version of the plug-in (provided you follow the installation instructions below).

If you have any suggestions to improve those translations, please leave a comment below.

How to install the plug-in

This plug-in is supported on Linux and Windows. It may work on the latest versions of macOS. The plug-in only works with GIMP 3. It does not work in GIMP 2.

If you want to be notified of any updates to this plug-in, please leave a comment below. I’ll use your email to notify you. And if you have any suggestions for enhancements, please also include them in a comment below.

If you run into any problems with any of the steps below, please let me know in the comments below.

1. Download the plug-in

Download the average image colour plug-in as a ZIP file. You’ll extract it as described below in the next section:

average-image-colour-v3.zip

2. Copy the downloaded file to where GIMP looks for plug-ins

This is something you have to do for every plug-in you add to GIMP. I discovered that the only reliable way is as follows.

Find where GIMP looks for plug-ins:

1. Open GIMP if it’s not already open and select Edit > Preferences in the GIMP menu.
2. In the Preferences dialog, scroll down the list on the left until you find Folders, then click on the expand icon in front of the word to expand that list.
3. Scroll down the list of folders and select Plug-ins.
4. Still in the Preferences dialog, on the Plug-in Folders panel on the right, to locate your plug-in folder(s). You can use the folder that’s listed for your user name or add a new one.
5. Click on the “Show file location in the file manager” to open your computer’s file manager.
6. Copy the .ZIP file you downloaded into that folder and extract it there. You should see a subfolder named “average-image-colour-v3”. The plug-in is inside that folder (see the note below for why it should be in its own subfolder). Don’t move it, just leave it in that subfolder.
7. Files downloaded from the internet or transferred across systems may not retain their “executable” flag, especially on UNIX-based systems like Linux. Windows 11 treats plug-in .py files as executable automatically. The .py file needs the correct permission to be executed as a script. It’s a quirk of the different operating systems’ security models.
   • Linux:
     You should be able to right click on the .py file and set the permission to allow it as an executable (see below for an example screenshot). Or you could set it in your Terminal app with the command chmod +x [PATH TO WHERE YOU EXTRACTED THE PLUG-IN FOLDER]/average-colour-layer-v3/average-colour-layer-v3.py. For example, with GIMP 3 I extracted the plug-in folder into a subfolder of Documents, so the command would be chmod +x "Documents/GIMP plug-ins/average-colour-layer-v3/average-colour-layer.py".
   • macOS:
     You may be able to right click on the .py file and set the permission to allow it as an executable (see below for an example screenshot). Otherwise, follow these instructions from Apple.

3. Register the plug-in with GIMP

Now you have to register the plug-in with GIMP: just close and re-open GIMP.

If all has gone according to plan, you should find a menu entry called Colours > Average colour. If not, please leave a comment below.

4. Optional: create a keyboard shortcut

If you want to assign a keyboard shortcut to a luminosity mask menu item, go right ahead:

These instructions are the same as for my other GIMP plug-ins (Interactive luminosity masks, Frequency separation, Dodge and burn). Only the plug-in names are changed.

Why it’s important to follow these steps

GIMP version 3.x requires that every plug-in must live in a folder with exactly the same name as the plug-in file. So for example, you add the subfolder where you’ve saved the plug-in file to the list of folders where GIMP looks for plug-ins, and that folder needs to be named exactly the same as the plug-in with that subfolder.

So for this situation, when you unzip the plug-in download, you should see a folder named “average-image-colour-v3” and that folder should contain a file, “average-image-colour-v3.py”. There will be other folders and files in that folder, leave them alone.

This is an example of how working with free software isn’t entirely free—you have to do some of the work that other systems automate, and put your thinking cap on. Bear in mind that GIMP is developed and maintained by volunteers who donate their time and talents as and when they can. So sometimes documentation lags behind development.