A lot of the time when you’re combining images, you’ll have to tweak the scale of one layer to make it fit better into the overall design. Whether you want to make everything look perfectly natural or create an ant the size of King Kong, the process is pretty simple – as long as you know what to watch out for.
There are three main ways that you can resize a layer in GIMP: the Scale tool, the Unified Transform tool, and the Scale Layer command.
For simplicity’s sake, I recommend using the Scale tool, but the Unified Transform tool can save you some time if you also need to apply any other transformations such as rotation or perspective distortion. The Scale Layer command is better for precision adjustments based on pixel size, rather than resizing your layer visually.
Resize A Layer Using the Scale Tool
This is my preferred method for scaling a layer since most of the work I do in GIMP depends on visual alignments rather than pixel-perfect calculations. It’s fast and easy, and there’s no risk of accidentally applying the wrong transform to your layer, which can happen if you use the Unified Transform tool instead.
Switch to the Scale tool by using the keyboard shortcut Shift + S. You can also find it in the toolbox, nested under the Unified Transform tool icon. Right-click or click and hold to see all the nested tools.
Select the layer you want to transform in the Layers panel, and then click on the main image window to begin the resizing process. GIMP adds handles around the layer boundaries that you can click and drag to resize your layer, and also adds a small popup overlay that lets you type in a new size if you’d prefer.
If you make a mistake, click the Reset button. Once you’re satisfied, click the Scale button, and you’re done!
Using the Unified Transform Tool
The Unified Transform tool is similar to the Free Transform option in Photoshop. It combines all the possible transform operations into a single tool, which can be very helpful, but you’ll have to pay close attention to your cursor to make sure you’re applying the correct transform operation.
Activate the Unified Transform tool in the toolbox, or by using the keyboard shortcut Shift + T. Select the layer you want to resize in the Layers panel, and then click on the main image window to begin resizing your layer.
As with the Scale tool, GIMP adds a bunch of handles around your image and a popup overlay, but the handles are more complex this time. Each different handle applies a different transform operation, so it’s a bit too easy to accidentally apply a tiny bit of perspective skew to your layer if you’re not paying close enough attention.
You also can’t manually enter a new size using this tool, and I find the Transform Matrix popup to be a lot more confusing (and less helpful) than the popups from other tools. For all these reasons, I recommend using the Scale tool method above until you’re more comfortable working with GIMP.
Using the Scale Layer Command
This is a more traditional approach to layer scaling, but I tend to prefer using the visual method described above. There are times when you need a bit more precision, though, and the Scale Layer command is perfect for that. The only downside is that there is no Preview option for visual confirmation of the final result.
To use it, open the Layer menu and select Scale Layer. GIMP opens the Scale Layer dialog box. Simply enter the new pixel dimensions of your image (or use whichever units you prefer by clicking the px dropdown box)
By default, the width and height settings are linked to maintaining the existing aspect ratio, but you can distort your layer during the scaling process by clicking the chain link icon between the two to unlink them.
For the Quality setting, Cubic interpolation is fine for the vast majority of cases, although if you discover any halo artifacts in your resized layer you can try using the other interpolation methods. LoHalo and NoHalo take longer to process, especially on very large layers, but they may provide a better result.
A Final Word
Those are all the different ways to resize a layer in GIMP! Resizing is one of those super-basic operations that should feel like second nature to a good image editor, so practice, practice, practice until you don’t even have to think about it!About Thomas Boldt