In this tutorial i will show you how you can change faces, or just adjust a picture into another picture without deleting anything. I will make a dog wear an uniform.

STEP 1.
Open both pictures, the picture with the uniform and the pet you want to use. Drag the picture of the pet over the one with the uniform and adjust the dimensions to match the dimension of the head of the officer.

STEP 2.
Now from Layer, add a Layer Mask- Reveal All and put your colors to defalt(back and white). Remember that black covers the picture in which you are working in the layer mask and white reveals it. So, being in the Layer mask use a hard/soft brush to hide the parts of the picture you don’t want to see using black and to bring up the elements from the background picture using the white.