If you’ve ever wanted to combine multiple photos into one eye-catching piece of digital artwork, layer masks are the technique that makes it possible. In this beginner-friendly GIMP tutorial from DCP Web Designers, you’ll learn how to blend three separate stock images – a light bulb, ocean waves, and a shark – into a single, polished composite that looks like a shark leaping out of water trapped inside a glowing light bulb.
Below is a complete walkthrough of the video, so you can follow along at your own pace or use it as a quick reference while you work.
What You'll Need
Before you start, download three free stock images (all sourced from Pixabay in the video):
- A light bulb image
- An ocean wave/water image
- A shark image
Step 1: Prep the Light Bulb Layer
Drag the light bulb image into GIMP as your base layer. Turn on View > Show Guides and drag a horizontal guideline down from the top of the canvas – this gives you a straight line to align the bulb against.
- Select the Rotate Tool and rotate the light bulb so it lies roughly flat along the guideline.
- Create a new white background layer and move it beneath the light bulb layer.
- Use the Rectangle Select tool to draw a selection around the bulb, then go to Layer > Crop to Selection to trim the canvas down.
- Turn off the guides (View > Show Guides) and deselect (Select > None).
- Rename the layer “Light Bulb” – naming layers as you go makes the project much easier to manage later.
Step 2: Clean Up the Light Bulb
Step 3: Add the Water Into the Bulb
Drag in your wave/water image and right-click it in the Layers panel to Add Alpha Channel.
- Select the light bulb layer, Edit > Copy it.
- Go back to the waves layer, right-click and Add Layer Mask, choosing Black (full transparency).
- Click the new black mask and paste (Ctrl+V) the copied light bulb shape – this clips the water so it only shows inside the bulb’s silhouette.
- Use the Move Tool to nudge the water into alignment with the bulb outline, then click the anchor icon to commit it.
- With the black mask still selected, paint with black on the mask to hide the excess water above the bulb’s rim, leaving just the section that reads as “water trapped inside glass.”
Save this as a new version.
Step 4: Add the Shark
Drag in the shark image, drop its layer opacity to around 70% so you can see through it while positioning, then use the Scale Tool (hold Shift to keep proportions) to size it appropriately – roughly so the shark’s mouth pokes just above the bulb’s rim. Once positioned, restore opacity to 100%.
Rename this layer “Shark,” then repeat the copy/mask trick from Step 3:
- Copy the light bulb shape, add a black, fully transparent layer mask to the shark layer, and paste the bulb shape into the mask.
- Use the Move Tool to align the shark with the bulb outline.
- Switch the mask’s paint color between white (adds back) and black (removes) to fine-tune which parts of the shark show through the bulb’s opening – this is the core trick behind layer masking in GIMP.
Step 5: Blend the Shark Into the Water
This is the most detail-oriented part of the tutorial. Zoom in close and use a small, soft brush to:
- Paint out the blue water color bleeding around the shark’s body and fins (using black on the mask).
- Leave in the splash/spray detail generated near the shark for a natural “bursting through the surface” look.
- Switch back to the water layer’s mask to restore any wave detail that got covered up, so the water still reads clearly around the bulb’s rim.
Take your time here – going over the edges a few passes, getting progressively closer each time, gives a much cleaner result than trying to nail it in one go.
Step 6: Merge, Resize, and Add a Shadow
Once you’re happy with the blend, merge the light bulb, water, and shark layers down into a single image (right-click > Merge Down, repeated).
- Use the Scale Tool to shrink the merged image slightly and the Move Tool to center it on the canvas.
- Create a new transparent layer named “Shadow.” Use the Ellipse Select tool to draw an oval beneath the bulb, fill it with black (Edit > Fill with FG Color), deselect, then apply Filters > Blur > Gaussian Blur (around 30–33px) to soften it into a realistic drop shadow.
Step 7: Add a Reflection
Duplicate the light bulb layer, flip the copy vertically (Tools > Transform Tools > Flip), and position it just below the original. Use the Unified Transform Tool to squash it to roughly half height, then drop its opacity down to around 7–8% so it reads as a subtle reflection rather than a mirror image.
Step 8: Add a Gradient Background
Create a new transparent layer named “Color BG.” Using the Color Picker, sample a blue tone from the shark for your foreground color, then select the Gradient Tool set to “FG to BG.” Hold Ctrl and drag from the top of the canvas downward to create a smooth color gradient behind your composite.
Step 9: Add a Glow Effect
For a final polish, duplicate the merged light bulb layer, apply Gaussian Blur (around 29px) to the duplicate, and place it behind the sharp version. This creates a soft glow radiating around the bulb’s edges, reinforcing the idea that it’s lit up.
Step 10: Export Your Final Image
When you’re happy with the result, flatten as needed and export via File > Export As, choosing JPEG as the file type.
Final Thoughts
This project is a great introduction to GIMP’s layer mask workflow, a technique you can reuse for almost any kind of photo composite. Once you understand how black/white painting on a mask reveals or hides content non-destructively, you can combine any set of images into surreal or polished creative artwork.
