How to Make a Collage in GIMP

Making a collage means a lot of different things to different people, so in this post, I’m going to cover three of the most common methods for combining pictures into collages: a simple square grid, a more flexible masonry-style grid, and a totally free form collage style that can open up whole new types of digital art for you. 

Method 1: Making a Square Grid Collage

A grid collage is fairly simple, as long as all your images are squares. Since that’s not usually the case, we’ll have to crop them all into squares before we can begin arranging them. A bit of very simple math, and we’ll have images that fit perfectly with a nice even border around each one.

Step 1: Decide The Dimensions

If your collage is just going to be viewed on-screen, you don’t need to worry too much about the pixel dimensions. GIMP doesn’t handle the CMYK colorspace used in printing, but if you’re going to print it, remember that you’ll need around 300 pixels per inch to create a good-looking print. 

Let’s use a basic grid of nine images arranged in a 3×3 grid for viewing on-screen in this example. You can make this as big as you want, of course, just scale the instructions upward a bit.

A grid of 3 images will have 2 gutters between the columns, and a border on each side. If each image is shown at 300 pixels wide, that makes for 900 pixels of image content per row. 

Add in an even amount of border for each gutter and border, for example, 25 pixels, and we get another 100 pixels total of border-spacing, so let’s make our image 1000 pixels square. 

Don’t worry about the DPI settings at this point if you’re just viewing on-screen

Create a new file with your chosen dimensions. If you’re creating a print-friendly file, you might want to set the X resolution and Y resolution settings to 300 dpi, but you can always do this later if necessary. 

Step 2: Open Files

To arrange all your images easily, you’ll want to place each one on a separate layer. You can do this by hand, or you can use the Open as Layers command from the File menu. 

This option works best when you have all your files stored in a single folder, which can also help you make your choices about which images to include in your collage. 

Using Open as Layers saves you time!

GIMP will place each image into a separate new layer for easy adjustment and arrangement.

Step 3: Resize and Crop

Now it’s time to scale and crop our layers. We calculated that each image would be 300 x 300, so we’ll need to scale each image’s shorter edge to be 300 pixels, and then crop it into a square. 

The Scale Layer command in GIMP 2.10

Select a layer in the Layers panel, then open the Layer menu and select Scale Layer.

In the dialog box, change the smaller of the two settings for your image to ensure easy cropping later on. In this example, I’ve changed the Height setting to 300 (though you can use whatever you’ve calculated for your grid). 

If your image is in portrait orientation instead of landscape, change the Width setting instead.

Switch to the Crop tool using the toolbox or the keyboard shortcut Shift + C. In the Tool Options panel, make sure the Current layer only box is checked, which will stop the crop boundaries from extending beyond your layer boundaries. 

The Tool Options panel shows settings for easily cropping your images into perfect squares

Also check the Fixed box, select Aspect Ratio from the dropdown menu, and type 1:1 into the dialog box below to set a perfectly square aspect ratio. 

Click and drag on your image to set the crop boundaries, using the handles to adjust as necessary. You can also click and drag in the center of the crop tool bounding box to move the current crop area. Just don’t crop too tightly or you might lose some image quality!

Scale and crop each layer into the desired size

Press Enter to finalize the crop when you’re ready. 

Repeat this for each layer, until they’re all neat squares. To keep things clear, you can use the layer visibility settings in the Layers panel to control which layers are visible while you’re working. 

Simply click the small eye icon beside each layer thumbnail to hide or show that layer as needed. 

Step 4: Arranging

If you don’t mind tedious projects, you can arrange each layer into the grid pattern by hand from now on using the Move tool and the rulers along the top and left side of the image window – but that takes forever!

Instead, let’s create some guides to help align everything. Open the Image menu, select the Guides submenu, and click New Guide.

Guides should speed things up and keep everything inline

You could create them by hand by clicking the rulers and dragging them out onto the image, but this allows you to place them more precisely. Since we calculated a 25-pixel border around each image, I’ll create the first one using the Horizontal direction at Position 25, meaning 25 pixels from the left edge of the image. 

The New Guide script makes placement simple

The next guide should be one image over, so it would be at Position: 325. The next would be at Position: 350, then at 650 and 675, and then at 975 for the last one. Repeat the same process using the Vertical direction until your grid of guides is complete. 

The guides make things much easier!

You should now be able to easily fit your image into the grid of guides using the Move tool. Select each layer in the Layers panel and place it where you want, and it should snap to match the edges of the guides. If it doesn’t, open the Edit menu and make sure that Snap to Guides is enabled.

Now you’ve got your images in a perfect grid!

Guides don’t show up when you export your final image, but you can hide them while you’re working by opening the View menu and turning off Show Guides.

Method 2: Making A Masonry Grid Collage

This might actually be the easiest type of collage to make because you don’t have to worry about cropping each image, but you will have to do some masking later to make everything fit neatly. 

Step 1: Create Your Working File

Create a new image in GIMP. For this example, I’ll stick with a size that will fit on an 8.5” x 11” sheet of paper so that I can print it easily, but you can use any size you want. 

Once again, using the Open as Layers command makes this process easy

Next, we’ll need to open all the images we want to include as separate layers. You can do this one by one if you want, although that can take a long time. It’s much faster to use the Open as Layers command, and then select all the images you want to use at once (assuming that they’re all in the same folder). 

Click the Open button and GIMP will open each image as a separate new layer automatically.

Step 2: Arrange Your Images

With each image on its own layer, you can begin to arrange the images using the Move command. Adjust the scale of each one to your chosen size using the Scale tool or the Unified Transform tool, whichever you find easiest. 

Rather than drive yourself crazy matching everything, use selections to finalize your grid!

You can try to calculate the various sizes of each image so that they fit perfectly using the background layer to provide the grid lines between each image, but if math isn’t your strong suit, the final step will use layer masks to separate everything neatly. 

Step 3: Patching the Gaps

To start adding neat grid lines between the images, we’ll use layer masks to hide parts of the images that are interfering with the grid. Select the layer that needs cropping, and add a layer mask by opening the Layers menu, selecting Mask, and choosing Add Layer Mask.


With the layer mask selected in the Layers panel, switch to the Ellipse Select tool by using the toolbox or the keyboard shortcut R. Select the edges that you want to remove, and fill that area of the layer mask with black pixels to crop out whatever is necessary to create a neat grid around your images. 

Using layer masks will allow you to experiment with different layout options without having to actually delete parts of your image and then re-add them if you change your mind. 

A Juniper collage!

Of course, if you’d prefer to make an even grid, then you can simply crop every photo into a square and place them precisely.

Method 3: Making A Freeform Collage

This is definitely the most flexible of the three techniques, but it also takes a lot more work to make it look natural (if you care about that, of course). Layer masks are far more powerful than we explored in Method 2, and you can use them to create natural transitions between each image. 

In fact, it’s possible to make the transitions so seamless that you can completely alter the content of an image, while still making it look like a natural, unedited photograph. This is where you really unlock the full power of image editors – creating photorealistic scenes that never actually happened. 

However, these projects can be as complex as you want them to be and are possibly worthy of a whole series of articles, so I’ll just explain the basics by placing a hawk from one image onto a more dramatic sky background. 

This is a great picture of a Red-tailed Hawk in flight, but the sky is very boring

Using the Open as Layers command, I’ve placed the hawk image in a new layer over top of my chosen dramatic sky background, and I’m going to quickly combine the two using a layer mask.

I simply add the layer mask and mask out all the blah grey clouds (a good selection with the Fuzzy Select tool makes this process faster).

Suddenly he’s flying before the storm!

Obviously, this is a very quick example and it doesn’t create a very believable effect, but that’s mostly caused by differences in the lighting angle and color between the two images. 

A slight adjustment using the Curves tool and the Hue-Saturation filter can improve the “rightness” of the image quite a lot, but there are many different tips and tricks to help blend images successfully. 

This technique is only limited by time, patience, and imagination. If you want to add more realistic objects, you can, but you don’t need to think in terms of photos – you can incorporate anything you want, from shapes to text to brushstrokes or even one of GIMP’s many filters. A freeform collage is all about your vision and your choices!

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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  • Neel

    hell! I can write phd thesis in the that time. GIMP might be very powerful but it’s the WORST when it comes to user interface.

    Reply
    • Thomas Boldt

      I agree that it definitely has some major UI issues, but hopefully the new version will correct a lot of those issues – if the developers ever finally release it!

      Reply