Hide part of an image and fill it with part of another image.
In the Layers panel, click the eye icon next to the bottom layer to temporarily hide it. (If the panel is not visible, choose Windows > Layers).
Note: This is a new feature in Photoshop. Make sure you’ve updated to the latest version!
Use the Quick Select tool to paint over an area you want to isolate. On your own image, it could be a background or any other area you want to knock out and replace with the image beneath. If you select too much of the image, hold Alt (Windows) or Option (Mac OS) while painting to subtract parts from the selection.
Experiment with the Transparency slider, on the Properties panel that appears when you choose Select and Mask, to see the areas you selected versus the unselected areas.
Under Output Settings in the Properties panel, choose to output the selection to a Layer Mask. Click OK.
Click the eye icon to make the bottom layer visible. You should see part of the bottom image showing through the area you defined for the top image.
Click the Layer Mask in the Layers panel to select it. Now, paint with black on the image to hide more of the top layer. Or, paint with white to reveal more of the top layer. Choose a softer brush or lower the opacity to create a softer transition in some areas.
It’s okay if you make a mistake. Just press Control+Z (Windows) or Command+Z (Mac OS) to undo.
We selected the Brush tool, chose a textured brush in the options bar, and then lowered the brush’s opacity. We set the foreground color to white and selected the Layer Mask by clicking it in the Layers panel. We then painted with white on the Layer Mask to reveal parts of the top image.