
Double exposure is an artistic technique in which a piece of photographic film is exposed twice to create a single photo. A little effort is required to create a double-exposed image with regular photographic film, but achieving this effect with an image editing app is a piece of cake.
Step 1
Open any image in Pixelmator.

Step 2
From your Desktop, select an additional image that you would like to blend with the current image and simply drag-and-drop it onto your composition to place it.

Step 3
If necessary, use the Move Tool (V) and the Transform tools (Edit > Transform) to position and scale the image so that it fits properly into the composition.

Step 4
In the Layers palette (View > Show Layers), select the image layer that is above the other layers and change its Blending to Overlay, as the Overlay blending mode combines layers equally.
If necessary, use the Eraser Tool (E) to get rid of the unwanted parts of either image (in our case, the visible edges of the second image).

Step 5
In order to equalize the colors in both images to match one color tone, first select both image layers and choose Layer > Duplicate Layers. Then choose Layer > Merge Layers. Once the layers are merged into one beautiful, double-exposed picture, use any of the color adjustment tools to enhance the results.
