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How Do I Mask a Layer in GIMP with Another Layer?

Published in GIMP Layer Masks 4 mins read

You can mask a layer in GIMP by adding a layer mask and then using another layer (or a copy of it) as the source for that mask. Here's how:

Steps to Mask a Layer in GIMP:

  1. Add a Layer Mask:

    • Right-click on the layer you want to mask in the Layers panel.
    • Select "Add Layer Mask..." from the context menu.
    • In the "Add Mask Options" dialog, choose the "White (full opacity)" option for a completely transparent mask, "Black (full transparency)" for a completely opaque mask, or another option as needed. Click "Add".

  2. Prepare the Mask Source (Layer):

    • The layer you intend to use as the mask source needs to influence the transparency of the target layer. Consider these options:
      • Use an existing layer: You can use any existing layer in your project. Make sure it's visible and positioned appropriately.
      • Create a new layer: Create a new layer and paint grayscale values onto it. White areas will make the target layer fully visible, black areas fully transparent, and shades of gray will create varying degrees of transparency.
      • Duplicate an existing layer: Duplicate a layer using Layer > Duplicate Layer. This is useful if you want to use a copy of the target layer as its own mask or a modified version of another layer.

  3. Copy and Paste as Mask:

    • Select the layer you want to use as the mask. This is the layer that will define the transparency. Make sure this layer is visible.
    • Copy the layer: Edit > Copy. If you're using a visible layer, you can copy its contents directly. Or if it is in the layers panel select the whole layer.
    • In the Layers panel, select the layer mask you just created (click on the mask thumbnail next to the layer thumbnail). A white outline should appear around it to indicate it's selected.
    • Paste into the mask: Edit > Paste. This will create a floating selection in the layer mask.
    • Anchor the Floating Selection: Layer > Anchor Layer. This merges the pasted content with the layer mask. Alternatively, you can click the green anchor icon in the Layers panel.

  4. Adjust the Mask (Optional):

    • You can now paint on the layer mask (using black, white, and shades of gray) to refine the masking effect.
    • Remember that white makes the layer visible, black makes it transparent, and gray values control the level of transparency.

  5. Disable/Enable the Mask (Optional):

    • You can temporarily disable the layer mask by Shift-clicking on the layer mask thumbnail in the Layers panel. This allows you to see the layer without the mask applied. Shift-click again to re-enable the mask.

Example Scenario:

Let's say you have a layer with a photo of a cat and you want to mask it with a text shape.

  1. Add a "Text" layer with the word "CAT".
  2. Right-click the cat photo layer and "Add Layer Mask...", using "White (full opacity)".
  3. Select the "CAT" text layer.
  4. Edit > Copy the "CAT" text layer.
  5. Select the layer mask of the cat photo (click on the white rectangle next to the cat photo layer).
  6. Edit > Paste, then Layer > Anchor Layer.

Now, only the part of the cat photo that overlaps the text "CAT" will be visible. The rest of the cat photo will be hidden, masked by the black (transparent) areas of the text.

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