How to Reduce Noise in GIMP

If you’ve ever tried to take a photo on your smartphone at night, you’ve seen the effect of digital noise: small white and colored pixels spread across your image.

These miscolored pixels are the result of an over-sensitive sensor trying to pull details out of the darkness, and they can really distract from the rest of your image. 

Modern digital cameras do an excellent job of minimizing digital noise in most situations, but many photos can still benefit from a little extra noise reduction in an image editor like GIMP.

Of course, it’s usually preferable to remove noise during the RAW conversion process, but that’s not always an option. 

Here’s how you can make your images look their best!

Using GIMP’s Noise Reduction Filter

GIMP has a built-in noise reduction filter, although it’s a bit basic by today’s standards. In a world of denoising tools that use machine learning techniques, the traditional approach to noise removal seems primitive by comparison, but it’s still a lot better than nothing!

This chipmunk is cute, but the digital noise is not

Open your noisy image in GIMP, and then open the Filters menu, select the Enhance submenu, and click Noise Reduction

GIMP will open the Noise Reduction dialog, which gives you only a single control option: Strength.

Higher Strength values will increase the noise reduction effect, but this will result in a significant loss of detail. 

The left side has the Noise Reduction with Strength 4 applied, and the right side is the original image

Notice that the chipmunk’s fur is much sharper on the unaltered side of the image (right). In the dark background, the noise is smoother on the left side, but it’s still pretty visible. 

This might be acceptable for some images, but it will be up to you to decide. If you’re not happy with the results, read on to learn about how to use the excellent G’MIC plugin collection for a few better ways to reduce noise in GIMP. 

Using the G’MIC Plugin Suite

According to the official website, “G’MIC is a full-featured open-source framework for digital image processing,” but part of that framework is a package of over 500+ different plugins for GIMP. If you enjoy playing with GIMP’s filter tools, you’ll absolutely love everything you can do with G’MIC – and best of all, it’s free!

Preparation: Installing G’MIC 

To install G’MIC, download a free copy of the software from the official developer’s website here. There are versions for Windows and Linux but no official support for macOS. Despite that, some Mac users have apparently had success making it work, and the developer lists all the information you’ll need if you want to try to use it on a Mac. 

If you’re installing on Windows 10 or later, you might get a warning notification when you try to launch the installation wizard. The warning looks a bit scary, as you can see below, but it’s nothing to be concerned about.

Click the More info link as highlighted above, and a new button will appear labeled Run anyway.

Click the Run anyway button, and the installation process will continue as intended. Follow the installation prompts until the installation process is completed. 

Finally, you have to restart GIMP to enable GMIC since GIMP only checks for new plugins when it launches

Launching G’MIC

Assuming that the installation process went smoothly, you should now have a new entry in the Filters menu. 

Open your noisy image in GIMP, and then open the Filters menu and click G’MIC-Qt near the bottom of the menu. 

The entire window can be resized, including the divisions between the preview window, filter list, and filter settings area. 

G’MIC opens up its own window with a large resizable preview window and a huge list of filters to play around with. Some are amazing, some are cool but also useless, and some are helpful. 

My favorite part about everything you can do with G’MIC is that you have the option to output every single filter onto a new layer. 

Just change the Output mode setting to New layer(s), and you can always preserve an unedited copy of your original image.

There are a surprising number of noise removal options available in G’MIC located in the Repair section of the filters list, well over 20 different methods, although they don’t all provide useful results. 

Of course, if you’re not happy with any of the noise reduction options I’ve chosen, feel free to experiment with the rest of G’MICs available filters. One of the best things about this plugin set is that it’s being updated quite regularly, unlike GIMP. 

Method 1: Denoise Smooth

This is one of the more modern entries in the G’MIC list of noise reduction options, and it does an excellent job of removing color noise. 

Just remember to note the Note section that says G’MIC’s preview is inaccurate. Although it doesn’t explain why, my guess is that because noise removal can be very CPU-intensive, GIMP and G’MIC don’t take the time to fully apply the algorithm to the preview window, only to your full image when you click Apply or OK

Left has the Denoise Smooth filter applied, right is the original

Unfortunately, it’s hard to accurately represent the difference using screenshots of noisy images because JPEG compression will automatically alter the results a bit, but this is an excellent method for removing color noise from an image, even if the screenshots don’t show it properly. 

Method 2: Smooth (Anisotropic)

Another way to reduce noise in GIMP with G’MIC is the Smooth (Anisotropic) filter. This is close to what GIMP’s Noise Reduction tool does natively, but you get a lot more control over the effect when using the G’MIC version. 

That being said, it’s possible to have too much of a good thing since G’MIC doesn’t provide any kind of documentation that helps explain what the various slider settings actually do. 

The most important settings are Amplitude and Sharpness, which balance out the strength of the noise removal effect against the loss of sharpness that comes with any noise removal processing. 

A Final Word

That covers a few of the best ways to reduce noise in GIMP, and now you also have a whole new set of GIMP plugins to experiment with.

There are over 500 filters in the G’MIC collection as of this writing, but they’re constantly updating it and adding new methods, so there may be a brand-new way to reduce noise in GIMP by the time you’re reading this!

Enjoy your noise-free images!

About Thomas Boldt
I’ve been working with digital images since the year 2000 or so, when I got my first digital camera. I've tried many image editing programs. GIMP is a free and powerful software, but not exactly user-friendly until you get comfortable with it, and I wanted to make the learning process easier for you here.

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