The Layer System
Layers are the single most important concept in GIMP. Everything else — masks, blending, compositing, retouching — is built on top of them. Master layers here and every subsequent session compounds faster.
Think of layers as transparent acetate sheets stacked on top of each other. Each sheet can contain its own drawing, photo, or adjustment — and you can edit any sheet without disturbing the ones above or below it. That isolation is the whole point.
In GIMP, layers are managed in the Layers panel (docked in Session 1). The topmost layer in the panel stack renders in front of everything below it. Transparency — represented by the grey-and-white checkerboard — passes through to the layer underneath wherever a layer has no pixel data.
The 80/20 operations you will use on almost every project: creating new layers, duplicating existing layers, reordering them, grouping them, adjusting opacity, toggling visibility, and merging or flattening when ready to export.
Skill unlock: After this session you can build any multi-element composition safely, knowing each element lives on its own layer and can be edited, moved, or deleted without destroying other parts of the image.
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01
Open an Image and Inspect the Layers Panel
Open any JPEG. In the Layers panel you'll see a single layer named "Background". Notice: it has a lock icon indicating it cannot be moved with the Move tool by default. This is GIMP's way of protecting the base image. Double-click the layer name and rename it "base" — good naming discipline starts now.
File → Open → inspect Layers panel (Windows → Dockable Dialogs → Layers) -
02
Create a New Transparent Layer
Click the "New Layer" button at the bottom of the Layers panel (the page icon), or use the menu. In the dialog that appears, set Fill with to "Transparency", give the layer a name such as "paint test", and click OK. The new layer appears above the base layer and is now the active layer — indicated by the highlight in the panel.
Layer → New Layer (Shift+Ctrl+N) → Fill with: Transparency -
03
Understand Layer Stacking Order
In the Layers panel, drag the "paint test" layer below the "base" layer. Notice the canvas — the paint test layer is now hidden behind the base image. Drag it back above "base". The rule: layers higher in the panel stack render in front of layers lower in the stack. Reorder at any time by dragging.
Drag layers in Layers panel to reorder. Or: Layer → Raise Layer / Lower Layer -
04
Duplicate a Layer
Click the "base" layer to select it, then duplicate it. This creates an exact copy directly above the original. Duplicating before applying any destructive operation (like painting, scaling, or a filter) is the single most effective safety habit in GIMP — you always have the original to fall back to. Rename the duplicate "base copy".
Layer → Duplicate Layer (Shift+Ctrl+D) — or right-click layer in panel → Duplicate Layer -
05
Control Layer Opacity
Select "base copy" in the Layers panel. At the top of the panel you'll see an Opacity slider (0–100). Drag it to 50% — the layer becomes semi-transparent and you can see through to the layer below. Opacity affects the entire layer uniformly. Set it back to 100% when done. Note: opacity is distinct from blend modes (covered in Session 3) — opacity simply scales transparency from fully opaque to fully invisible.
Layers panel → Opacity slider (top of panel) -
06
Toggle Layer Visibility
Click the eye icon to the left of any layer in the panel to hide it. The layer is not deleted — it's simply not rendered. This is essential for comparing before/after states: toggle the top layer's eye on and off to see what the layer is contributing. Click the eye again to restore visibility.
Click the eye icon (👁) to the left of the layer thumbnail in the Layers panel -
07
Create and Use a Layer Group
When a project has many layers, groups keep them organised. Click the "New Layer Group" button at the bottom of the Layers panel (the folder icon), or use the menu. Name it "adjustments". Drag your "paint test" and "base copy" layers into the group by dropping them onto the group name. Click the triangle next to the group name to collapse or expand it. Layer groups can also have their own opacity and blend mode, which affects all layers inside them.
Layer → New Layer Group — then drag layers into it in the Layers panel -
08
Understanding Floating Selections
When you paste content in GIMP (Ctrl+V), it arrives as a "Floating Selection" — a temporary layer that must be handled before you can work on anything else. You have two choices: click "New Layer" in the Layers panel to promote it to a permanent named layer, or click "Anchor Layer" (the anchor icon) to merge it down into the active layer below. Understanding this prevents the common "I can't draw on my layer" confusion.
Edit → Paste (Ctrl+V) → Layers panel → New Layer button (to promote) or Anchor icon (to merge down) -
09
Merge Down vs Flatten Image
Two destructive operations for combining layers — use them only when you're certain. Merge Down (Ctrl+M) combines the active layer with the one immediately below it into a single layer. Flatten Image merges every layer into a single Background layer, discarding all transparency, groups, and layer information. Use Flatten only immediately before export — never as part of your working process. To export without flattening, use File → Export As rather than File → Save.
Layer → Merge Down (Ctrl+M) | Image → Flatten Image -
10
Layer Boundary vs Canvas Size
In GIMP, a layer can be larger or smaller than the canvas. If you scale a layer up beyond the canvas edges, the pixel data still exists — it's just clipped from view. To see what's outside the canvas, use View → Shrink Wrap. To resize a layer to match the canvas exactly, use Layer → Layer to Image Size. To resize the canvas to fit all layers, use Image → Fit Canvas to Layers.
Layer → Layer to Image Size | Image → Fit Canvas to Layers
Critical habit: Always work on a named, duplicate layer. Never paint, filter, or adjust directly on your only copy of a layer. If it goes wrong, you want an undo path — duplicate first.
Open any photograph. You will build a simple four-layer file from scratch, performing every key layer operation from the core technique section.
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A
Set up the base
Open a photo. Rename the background layer "photo". Duplicate it and name the copy "photo — working copy". Toggle the original "photo" layer's visibility off so it acts as a safe backup. All your work will be on "photo — working copy".
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B
Add a solid-colour overlay layer
Create a new layer above "photo — working copy" (Shift+Ctrl+N), fill type "Foreground Color". Set your foreground colour to a bright red (click the foreground colour swatch in the Toolbox, enter #FF0000). Name this layer "colour overlay". Set its opacity to 30% and observe the tinted result.
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C
Create a layer group and organise
Create a layer group named "working layers". Move both "photo — working copy" and "colour overlay" into it. Collapse the group. Verify the image looks identical — grouping does not affect appearance. Set the group's opacity to 80% and note the effect on the entire group simultaneously.
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D
Paste and anchor
Copy any small image to your clipboard (or copy a selection from within GIMP). Press Ctrl+V to paste. The Floating Selection appears. Use the Layers panel to promote it to its own layer (click New Layer). Name it "pasted element". Toggle its visibility on and off.
Expected result: Your Layers panel should contain: a hidden "photo" layer at the bottom, a "working layers" group above it, and a "pasted element" layer at the top. This 3-level structure (backup → groups → working layers) is the foundation of professional GIMP organisation.
No step-by-step guidance. Attempt the following using only what you've learned today:
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Open two separate photos and combine them into one file
Open Photo A as your main canvas. Open Photo B separately. In Photo B, select all (Ctrl+A), copy (Ctrl+C), then switch to Photo A and paste (Ctrl+V). Promote the floating selection to its own layer. Resize Photo B's layer using the Scale tool so both images are visible. What happens when you reorder the two photo layers?
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Experiment with layer opacity to blend the two images
Set the top photo layer's opacity to 50%. What do you see? Try 25%, then 75%. Think about what this could be useful for — watermarks, double exposures, ghosting effects. We'll formalise this in Session 3 with blend modes.
Hint: If the pasted photo layer doesn't fill the canvas, make sure the layer is selected and use the Scale tool (Shift+S) to resize it, then the Move tool (M) to reposition it.
Session 2 Review
- Layers are independent, stackable sheets of pixel data
- Higher layers in the panel stack render in front of lower layers
- Transparency shows as a grey-white checkerboard; it passes through to the layer below
- A Floating Selection must be anchored or promoted before editing continues
- Flatten Image is destructive — use Export As to preserve layers
- A layer can extend beyond the canvas boundary — data is preserved, just clipped
- Editing the wrong layer (always check which layer is highlighted in the panel)
- Using File → Save instead of File → Export As — GIMP's native .xcf format preserves layers; JPEG/PNG do not
- Flattening the image mid-workflow and losing all layer separation
- Ignoring the Floating Selection — not anchoring or promoting it before continuing
- Confusing Layer opacity (uniform transparency) with blend modes (mathematical blending)
- What keyboard shortcut duplicates a layer?
- What are the two ways to handle a Floating Selection?
- What is the difference between Merge Down and Flatten Image?
- If a layer is invisible, has it been deleted?
- Which file format preserves all layers when saving in GIMP?
- Session 3 covers Layer Blend Modes — how layers interact mathematically with layers beneath them
- The same layer panel you set up today will be your workshop for blend modes
- Bring the two-photo file you made in the stretch challenge — you'll use it in Session 3 to test blend modes live
- No new tools needed — blend modes are controlled entirely from the Layers panel dropdown
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01
GIMP Official Docs Authoritative reference for every tool, dialog, and preference in GIMP 3.x.
docs.gimp.org ↗ -
02
Davies Media Design Video walkthroughs specifically for GIMP 3.x — best free companion to this course.
YouTube ↗ -
03
GIMP Forums Community support for troubleshooting, plug-in questions, and workflow advice.
gimp-forum.net ↗