Open one portrait photo in Photoshop.
Go to File – Place
Choose the background File Image
Click Ok to place the image.
Rename your layers. One should be called portrait and the other background image.
Now your layer palette should look like this:
Right click the background image and rasterize the layer.
Turn off the visibly of your background image layer.
Select the subject (person) of your portrait image
make sure your are on your portrait layer and click the Mask button on the layers palette
Your layer palette should look like this.
Turn off the visibility of the portrait image layer and turn on the visibility of the background image.
Go to Edit – Define Brush Preset
Name your brush
click to make the background image visible and make the portrait image invisible.
Add a layer mask to the background image layer
Using your paintbrush with your new brush design click one time on the layer mask, making sure that your fill is set to the color black.
With the background image layer selected go to EDIT – Invert
Add a new layer by clicking on the layer icon on the layer palette. Move the layer to the bottom of the stack.
Fill the layer with White by going to Edit – Fill
your final result should look something like this below. Save as a jpg and turn into canvas.