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GIMP Tutorial: Whiten a dull background

Kat Landreth from Pare & Focus shows how easy it is to whiten a dull background in GIMP.

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Words and images by Kat Landreth the writer for - a site for budget friendly photography tips, tricks, and tutorials.

It bugs me when I think the background in my photo is white when it’s really off white. Even if the background of my photos is just a little darker than white it’s obvious when I upload it to my white website.

Check out this image:

Grey background

The gray GIMP background makes my photo’s background look white in comparison. But trust me, it’s not white.

That made me think. Maybe I could change my GIMP background to mimic my website. So I did. Now when I use a simple levels adjustment to whiten the background I know it’s perfect before I upload.

Make GIMP mimic a white website:

1. Open

Open your photo in GIMP.

2. Preferences

Go to Edit > Preferences in the main GIMP window. The Preferences window will appear.

Preferences in the main GIMP window


3. Expand Image Windows

Expand the Image Windows options on the left side of the window by clicking the little arrow that’s next to it. Choose Appearance.

4. Custom Colour

Choose Custom Colour from the drop down menu next to the words Canvas Padding Mode on the right portion of the Preferences menu.

5. Custom Padding Colour

Make sure the Custom Padding Colour is white. If the little box is not white click it and choose white from the color options. Click OK.


Is there a yellow and black dotted line around your image? If that’s turned on you won’t get the full effect of mimicking a white website. Here’s how to turn it off:

6. View

Go to View in the main GIMP window.

7. Uncheck a box

Uncheck the box next to Show Layer Boundary.

Now that my photo is displayed against a really white background I can see at a glance what’s not white. As I make corrections I can easily tell when I’ve got it just right.

Show layer boundary

Whiten a dull background with levels:

1. Duplicate the background layer

Duplicate the background layer by holding Shift + Ctrl + D on your keyboard.

2. Levels

Go to Colors > Levels in the main GIMP window. The levels window will appear.

Adjust colour levels
There’s a lot in this window but you can ignore most of it. (I highlighted the important parts in the above image) You only have to do two things: number one, Make sure the Channel dropdown menu is set to Value and number two, grab the little arrow under the top histogram on it’s far right side and start slowly dragging it to the left.

As you drag the arrow you should notice your white background getting whiter. When it’s perfectly white it will blend seamlessly into the GIMP background. Click OK.

If your whole photo needed lightening it might look perfect now. But making this adjustment might make your subject too bright. That’s easy to fix with a layer mask.

Tone down the effect on your subject:

1. Add Layer Mask

Right Click the Background copy layer and choose Add Layer Mask from the menu that appears. A Layer Mask window will appear. Choose White (Full Opacity) and click Add.

2. Paintbrush

Grab the Paintbrush from the Toolbox window by double clicking it. I like to use a Fuzzy brush. I set the Opacity of the brush to 50% to start.

3. Foreground colour

Make sure the Foreground Color is set to Black.

4. Select the Layer Mask

Make sure the layer mask is selected (the layer icon will have a black border around it, the layer mask icon will have a white border).

5. Paint

Paint over areas that are too bright in the main GIMP window.

Paint tool

You should notice the subject start to change back to normal brightness as you paint. If it’s not getting toned down enough just turn up the opacity of the brush and keep painting.

You can see what my layer mask looked like when I was done here:

Layer Mask

I turned up the opacity of the brush for the wooden block portion of the picture. That part of the mask looks black. The soft brush prevented hard lines between the areas I masked and the areas I kept bright.

When everything is perfect you can merge the visible layers and finish doing any editing you have left to do.

It just gets easier

You only have to set up GIMP once for this trick. Even if you close GIMP and restart it your new appearance settings will be saved. Instead of following all of the steps in this tutorial you’ll only have to follow the Levels and Layer Mask part. Pretty cool, eh?

I leave GIMP set up like this most of the time. So much of the work I do ends up online and more often than not it’s on websites with white backgrounds. It’s incredibly handy to have GIMP mimic the look of those white websites. I know my pictures will look great before I upload and I only have to edit them once.

Kat Landreth is the writer for - a site for budget friendly photography tips, tricks, and tutorials.

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